基本情報

所属

• 理学研究院　物理学部門　電子物性物理学分野

職名

• 教授

学位

• 博士（理学）

科研費研究者番号

• 70204211

J-Global ID

• 200901073664479708

研究キーワード

• 走査トンネル顕微鏡/分光   Solid state physics II   

研究分野

• 自然科学一般 / 磁性、超伝導、強相関系

担当教育組織

•  学士課程　理学部
•  修士課程　理学院
•  博士課程　理学院

学歴

•         - 1984年   北海道大学   理学研究科   物理学
•         - 1984年   北海道大学
•         - 1982年   北海道大学   理学部   物理学
•         - 1982年   北海道大学

所属学協会

• 米国物理学会   日本物理学会   

研究活動情報

論文

• Dielectric response in the antiferromagnetic phase of Fe1.10Te

  Kazuoki Yokoi, Issei Miyazaki, Koichi Ichimura, Satoshi Tanda, Noriaki Matsunaga, Tohru Kurosawa, Migaku Oda

  Solid State Communications 371 115262 - 115262 2023年10月
• Optical vortex induced spatio-temporally modulated superconductivity in a high-T_c cuprate

  Yasunori Toda, Satoshi Tsuchiya, Keisaku Yamane, Ryuji Morita, Migaku Oda, Tohru Kurosawa, Tomaz Mertelj, Dragan Mihailovic

  Optics Express 31 11 17537 - 17537 2023年05月10日 [査読有り]
   

  We report an experimental approach to produce spatially localized photoinduced superconducting state in a cuprate superconductor using optical vortices with ultrafast pulses. The measurements were carried out using coaxially aligned three-pulse time-resolved spectroscopy, in which an intense vortex pulse was used for coherent quenching of superconductivity and the resulting spatially modulated metastable states were analyzed by the pump-probe spectroscopy. The transient response after quenching shows a spatially localized superconducting state that remains unquenched at the dark core of the vortex beam for a few picoseconds. Because the quenching is instantaneously driven by photoexcited quasiparticles, the vortex beam profile can be transferred directly to the electron system. By using the optical vortex-induced superconductor, we demonstrate spatially resolved imaging of the superconducting response and show that the spatial resolution can be improved using the same principle as that of super-resolution microscopy for fluorescent molecules. The demonstration of spatially controlled photoinduced superconductivity is significant for establishing a new method for exploring novel photoinduced phenomena and applications in ultrafast optical devices.
• Fate of charge order in overdoped La-based cuprates

  K. von Arx, Qisi Wang, S. Mustafi, D. G. Mazzone, M. Horio, D. John Mukkattukavil, E. Pomjakushina, S. Pyon, T. Takayama, H. Takagi, T. Kurosawa, N. Momono, M. Oda, N. B. Brookes, D. Betto, W. Zhang, T. C. Asmara, Y. Tseng, T. Schmitt, Y. Sassa, J. Chang

  npj Quantum Materials 8 1 2023年01月19日 [査読有り]
   

  Abstract In high-temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with a commensuration of eight and four lattice units, respectively. How this stripe order evolves across optimal doping remains a controversial question. Here we present a systematic resonant inelastic x-ray scattering study of weak charge correlations in La_2−xSr_xCuO₄ and La_1.8−xEu_0.2Sr_xCuO₄. Ultra high energy resolution experiments demonstrate the importance of the separation of inelastic and elastic scattering processes. Long-range temperature-dependent stripe order is only found below optimal doping. At higher doping, short-range temperature-independent correlations are present up to the highest doping measured. This transformation is distinct from and preempts the pseudogap critical doping. We argue that the doping and temperature-independent short-range correlations originate from unresolved electron–phonon coupling that broadly peaks at the stripe ordering vector. In La_2−xSr_xCuO₄, long-range static stripe order vanishes around optimal doping and we discuss both quantum critical and crossover scenarios.
• Uniaxial pressure induced stripe order rotation in La1.88Sr0.12CuO4

  Qisi Wang, K. von Arx, D. G. Mazzone, S. Mustafi, M. Horio, J. Küspert, J. Choi, D. Bucher, H. Wo, J. Zhao, W. Zhang, T. C. Asmara, Y. Sassa, M. Månsson, N. B. Christensen, M. Janoschek, T. Kurosawa, N. Momono, M. Oda, M. H. Fischer, T. Schmitt, J. Chang

  Nature Communications 13 1 2022年12月 [査読有り][通常論文]
   

  Abstract Static stripe order is detrimental to superconductivity. Yet, it has been proposed that transverse stripe fluctuations may enhance the inter-stripe Josephson coupling and thus promote superconductivity. Direct experimental studies of stripe dynamics, however, remain difficult. From a strong-coupling perspective, transverse stripe fluctuations are realized in the form of dynamic “kinks”—sideways shifting stripe sections. Here, we show how modest uniaxial pressure tuning reorganizes directional kink alignment. Our starting point is La_1.88Sr_0.12CuO₄ where transverse kink ordering results in a rotation of stripe order away from the crystal axis. Application of mild uniaxial pressure changes the ordering pattern and pins the stripe order to the crystal axis. This reordering occurs at a much weaker pressure than that to detwin the stripe domains and suggests a rather weak transverse stripe stiffness. Weak spatial stiffness and transverse quantum fluctuations are likely key prerequisites for stripes to coexist with superconductivity.
• Single-domain stripe order in a high-temperature superconductor

  Gediminas Simutis, Julia Küspert, Qisi Wang, Jaewon Choi, Damian Bucher, Martin Boehm, Frédéric Bourdarot, Mads Bertelsen, Chennan N Wang, Tohru Kurosawa, Naoki Momono, Migaku Oda, Martin Månsson, Yasmine Sassa, Marc Janoschek, Niels B. Christensen, Johan Chang, Daniel G. Mazzone

  Communications Physics 5 1 2022年11月21日 [査読有り]
   

  Abstract The coupling of spin, charge and lattice degrees of freedom results in the emergence of novel states of matter across many classes of strongly correlated electron materials. A model example is unconventional superconductivity, which is widely believed to arise from the coupling of electrons via spin excitations. In cuprate high-temperature superconductors, the interplay of charge and spin degrees of freedom is also reflected in a zoo of charge and spin-density wave orders that are intertwined with superconductivity. A key question is whether the different types of density waves merely coexist or are indeed directly coupled. Here we profit from a neutron scattering technique with superior beam-focusing that allows us to probe the subtle spin-density wave order in the prototypical high-temperature superconductor La$${}_{1.88}$$Sr$${}_{0.12}$$CuO$${}_{4}$$ under applied uniaxial pressure to demonstrate that the two density waves respond to the external tuning parameter in the same manner. Our result shows that suitable models for high-temperature superconductivity must equally account for charge and spin degrees of freedom via uniaxial charge-spin stripe fluctuations.
• Pseudogap suppression by competition with superconductivity in La-based cuprates

  J. Küspert, R. Cohn Wagner, C. Lin, K. von Arx, Q. Wang, K. Kramer, W. R. Pudelko, N. C. Plumb, C. E. Matt, C. G. Fatuzzo, D. Sutter, Y. Sassa, J.-Q. Yan, J.-S. Zhou, J. B. Goodenough, S. Pyon, T. Takayama, H. Takagi, T. Kurosawa, N. Momono, M. Oda, M. Hoesch, C. Cacho, T. K. Kim, M. Horio, J. Chang

  Physical Review Research 4 4 2022年10月10日 [査読有り]
  
• Competition between spin ordering and superconductivity near the pseudogap boundary in La2-xSrxCuO4 : Insights from NMR

  I. Vinograd, R. Zhou, H. Mayaffre, S. Krämer, S. K. Ramakrishna, A. P. Reyes, T. Kurosawa, N. Momono, M. Oda, S. Komiya, S. Ono, M. Horio, J. Chang, M.-H. Julien

  Physical Review B 106 5 2022年08月31日 [査読有り]
  
• Evidence for a Square-Square Vortex Lattice Transition in a High-Tc Cuprate Superconductor

  D. J. Campbell, M. Frachet, S. Benhabib, I. Gilmutdinov, C. Proust, T. Kurosawa, N. Momono, M. Oda, M. Horio, K. Kramer, J. Chang, M. Ichioka, D. LeBoeuf

  Physical Review Letters 129 6 2022年08月02日 [査読有り]
  
• Unveiling Unequivocal Charge Stripe Order in a Prototypical Cuprate Superconductor

  J. Choi, Q. Wang, S. Jöhr, N. B. Christensen, J. Küspert, D. Bucher, D. Biscette, M. H. Fischer, M. Hücker, T. Kurosawa, N. Momono, M. Oda, O. Ivashko, M. v. Zimmermann, M. Janoschek, J. Chang

  Physical Review Letters 128 20 2022年05月20日 [査読有り]
  
• Charge density waves in cuprate superconductors beyond the critical doping

  H. Miao, G. Fabbris, R. J. Koch, D. G. Mazzone, C. S. Nelson, R. Acevedo-Esteves, G. D. Gu, Y. Li, T. Yilimaz, K. Kaznatcheev, E. Vescovo, M. Oda, T. Kurosawa, N. Momono, T. Assefa, I. K. Robinson, E. S. Bozin, J. M. Tranquada, P. D. Johnson, M. P. M. Dean

  npj Quantum Materials 6 1 2021年12月 [査読有り]
   

  The unconventional normal-state properties of the cuprates are often discussed in terms of emergent electronic order that onsets below a putative critical doping of x_c ≈ 0.19. Charge density wave (CDW) correlations represent one such order; however, experimental evidence for such order generally spans a limited range of doping that falls short of the critical value x_c, leading to questions regarding its essential relevance. Here, we use X-ray diffraction to demonstrate that CDW correlations in La_2−xSr_xCuO₄ persist up to a doping of at least x = 0.21. The correlations show strong changes through the superconducting transition, but no obvious discontinuity through x_c ≈ 0.19, despite changes in Fermi surface topology and electronic transport at this doping. These results demonstrate the interaction between CDWs and superconductivity even in overdoped cuprates and prompt a reconsideration of the role of CDW correlations in the high-temperature cuprate phase diagram.
• High magnetic field ultrasound study of spin freezing in La1.88Sr0.12CuO4

  M. Frachet, S. Benhabib, I. Vinograd, S.-F. Wu, B. Vignolle, H. Mayaffre, S. Krämer, T. Kurosawa, N. Momono, M. Oda, J. Chang, C. Proust, M.-H. Julien, D. LeBoeuf

  Physical Review B 103 11 2021年03月18日 [査読有り]
  
• Coexistence of checkerboard and quasiparticle interference modulations in Bi2Sr2CaCu2O8+x studied by scanning tunneling microscopy/spectroscopy

  Shusei Mizuta, Migaku Oda, Naoki Momono, Hiroyuki K. Yoshida, Masayuki Ido

  PHYSICAL REVIEW B 102 18 2020年11月 [査読有り]
   

  We performed scanning tunneling microscopy/spectroscopy measurements in the superconducting state of underdoped Bi(2)Sr(2)CaCu(2)O(8+x )and demonstrated that the checkerboard (CB) and Bogoliubov quasiparticle interference (QPI) modulations, which are considered to be characteristic features for the low-energy states around the antinodal and nodal regions of the Fermi surface, respectively, coexist in identical regions of the Cu-O plane. In the present work, these electronic superstructures are successfully separated from each other, and the local amplitude and phase are evaluated for the CB modulation and the q(1) component of QPI, which are characterized by similar wave vectors. The q(1)-QPI component tends to be in-phase and antiphase with the CB modulation for positive and negative bias voltages, respectively. The significant spatial phase relationship is confirmed in regions where the local amplitude of CB modulation is comparatively large. This finding implies an interplay between the QPI and CB modulations.
• Hidden magnetism at the pseudogap critical point of a cuprate superconductor

  Mehdi Frachet, Igor Vinograd, Rui Zhou, Siham Benhabib, Shangfei Wu, Hadrien Mayaffre, Steffen Kramer, Sanath K. Ramakrishna, Arneil P. Reyes, Jerome Debray, Tohru Kurosawa, Naoki Momono, Migaku Oda, Seiki Komiya, Shimpei Ono, Masafumi Horio, Johan Chang, Cyril Proust, David LeBoeuf, Marc-Henri Julien

  NATURE PHYSICS 16 10 1064 - + 2020年10月 [査読有り]
   

  NMR and ultrasound measurements show that the spin-glass phase exists in a cuprate all the way up to the doping that marks the end of the pseudogap phase. This highlights the possible connection between the pseudogap and Mott physics.The nature of the pseudogap phase of hole-doped cuprate superconductors is still not understood fully. Several experiments have suggested that this phase ends at a critical hole doping levelp*, but the nature of the ground state for lower doping is still debated. Here, we use local nuclear magnetic resonance and bulk ultrasound measurements to show that, once competing effects from superconductivity are removed by high magnetic fields, the spin-glass phase of La(2-x)Sr(x)CuO(4)survives up to a doping level consistent withp*. In this material, the antiferromagnetic-glass phase extends from the doped Mott insulator atp= 0.02 up top* approximate to 0.19, which provides a connection between the pseudogap and the physics of the Mott insulator. Furthermore, the coincidence of the pseudogap boundary with a magnetic quantum phase transition in the non-superconducting ground state has implications for the interpretation of other experiments, particularly for transport and specific-heat measurements in high magnetic fields.
• High-pressure synthesis, crystal structure, and magnetic properties of the Shastry-Sutherland-lattice oxides BaLn2ZnO5 (Ln = Pr, Sm, Eu)

  Yuto Ishii, Jie Chen, Hiroyuki K. Yoshida, Migaku Oda, Andrew D. Christianson, Kazunari Yamaura

  Journal of Solid State Chemistry 289 121489 - 121489 2020年09月 [査読有り]
  
• Impurity Effects on Superconductivity of LaO1-xFxBi1-ySbyS2 through Specific Heat Measurements

  Ying Wang, Shotaro Takahashi, Takaya Suda, Taro Tamura, Haruka Ohta, Tohru Kurosawa, Migaku Oda, Masayuki Ido, Naoki Momono

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 89 9 2020年09月 [査読有り]
   

  In this study, we illustrate the effect of Sb substitution on a single crystal of the layered superconductor LaO1-xFxBi1-ySbyS2 through specific heat measurements. LaO1-xFxBiS2 (x = 0.4 and 0.5) and LaO0.5F0.5Bi1-ySbyS2 (y = 0 -0.20) were synthesized by the flux method under ambient pressure. The electronic specific heat C-e of LaO1-xFxBiS2 (x = 0.4 and 0.5) below similar to T-c can be explained by s-wave superconductivity with either a single gap or two gaps. The C-e/T at T <= T-c in LaO0.5F0.5Bi1-ySbyS2 below y = 0.06 is hardly recovered by Sb substitution, indicating that the superconductivity is robust against nonmagnetic impurities.
• q=0 long-range magnetic order in centennialite CaCu3(OD)6Cl2·0.6D2O: A spin-12 perfect kagome antiferromagnet with J1−J2−Jd

  K. Iida, H. K. Yoshida, A. Nakao, H. O. Jeschke, Y. Iqbal, K. Nakajima, S. Ohira-Kawamura, K. Munakata, Y. Inamura, N. Murai, M. Ishikado, R. Kumai, T. Okada, M. Oda, K. Kakurai, M. Matsuda

  Physical Review B 101 22 2020年06月22日 [査読有り]
   

  Crystal and magnetic structures of the mineral centennialite CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O are investigated by means of synchrotron x-ray diffraction and neutron diffraction measurements complemented by density functional theory (DFT) and pseudofermion functional renormalization group (PFFRG) calculations. CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O crystallizes in the P (3) over bar m1 space group and Cu2+ ions form a geometrically perfect kagome network with antiferromagnetic J(1). No intersite disorder between Cu2+ and Ca2+ ions is detected. CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O enters a magnetic long-range ordered state below T-N = 7.2 K, and the q = 0 magnetic structure with negative vector spin chirality is obtained. The ordered moment at 0.3 K is suppressed to 0.58(2)mu(B). Our DFT calculations indicate the presence of antiferromagnetic J(2) and ferromagnetic J(d) superexchange couplings of a strength which places the system at the crossroads of three magnetic orders (at the classical level) and a spin-1/2 PFFRG analysis shows a dominance of q = 0 type magnetic correlations, consistent with and indicating proximity to the observed q = 0 spin structure. The results suggest that this material is located close to a quantum critical point and is a good realization of a J(1)-J(2)-J(d) kagome antiferromagnet.
• Strongly Correlated Charge Density Wave in La2−xSrxCuO4 Evidenced by Doping-Dependent Phonon Anomaly

  J. Q. Lin, H. Miao, D. G. Mazzone, G. D. Gu, A. Nag, A. C. Walters, M. García-Fernández, A. Barbour, J. Pelliciari, I. Jarrige, M. Oda, K. Kurosawa, N. Momono, Ke-Jin Zhou, V. Bisogni, X. Liu, M. P. M. Dean

  Physical Review Letters 124 20 2020年05月21日 [査読有り]
  
• High-Temperature Charge-Stripe Correlations in La1.675Eu0.2Sr0.125CuO4

  Qisi Wang, M. Horio, K. von Arx, Y. Shen, D. John Mukkattukavil, Y. Sassa, O. Ivashko, C. E. Matt, S. Pyon, T. Takayama, H. Takagi, T. Kurosawa, N. Momono, M. Oda, T. Adachi, S. M. Haidar, Y. Koike, Y. Tseng, W. Zhang, J. Zhao, K. Kummer, M. Garcia-Fernandez, Ke-Jin Zhou, N. B. Christensen, H. M. Ronnow, T. Schmitt, J. Chang

  PHYSICAL REVIEW LETTERS 124 18 2020年05月 [査読有り]
   

  We use resonant inelastic x-ray scattering to investigate charge-stripe correlations in La1.675Eu0.2Sr0.125CuO4. By differentiating elastic from inelastic scattering, it is demonstrated that charge-stripe correlations precede both the structural low-temperature tetragonal phase and the transport-defined pseudogap onset. The scattering peak amplitude from charge stripes decays approximately as T-2 towards our detection limit. The in-plane integrated intensity, however, remains roughly temperature independent. Therefore, although the incommensurability shows a remarkably large increase at high temperature, our results are interpreted via a single scattering constituent. In fact, direct comparison to other stripe-ordered compounds (La1.875Ba0.125CuO4, La1.475Nd0.4Sr0.125CuO4, and La1.875Sr0.125CuO4) suggests a roughly constant integrated scattering intensity across all these compounds. Our results therefore provide a unifying picture for the charge-stripe ordering in La-based cuprates. As charge correlations in La1.675Eu0.2Sr0.125CuO4 extend beyond the low-temperature tetragonal and pseudogap phase, their emergence heralds a spontaneous symmetry breaking in this compound.
• Thermal-transport studies of kagomé antiferromagnets

  M. Yamashita, M. Akazawa, M. Shimozawa, T. Shibauchi, Y. Matsuda, H. Ishikawa, T. Yajima, Z. Hiroi, M. Oda, H. Yoshida, H.-Y. Lee, J. H. Han, N. Kawashima

  Journal of Physics: Condensed Matter 32 7 074001  2020年 [査読有り][通常論文]
   

  Searching for the ground state of a kagom Heisenberg antiferromagnet (KHA) has been one of the central issues of condensed-matter physics, because the KHA is expected to host spin-liquid phases with exotic elementary excitations. Here, we show our longitudinal () and transverse () thermal conductivities measurements of the two kagom materials, volborthite and Ca kapellasite. Although magnetic orders appear at temperatures much lower than the antiferromagnetic energy scale in both materials, the nature of spin liquids can be captured above the transition temperatures. The temperature and field dependence of is analyzed by spin and phonon contributions, and large sample variations of the spin contribution are found in volborthite. Clear changes in are observed at the multiple magnetic transitions in volborthite, showing different magnetic thermal conduction in different magnetic structures. These magnetic contributions are not clearly observed in low- crystals of volborthite, and are almost absent in Ca kapellasite, showing the high sensitivity of the magnetic excitation in to the defects in crystals. On the other hand, a clear thermal Hall signal has been observed in the lowest- crystal of volborthite and in Ca kapellasite. Remarkably, both the temperature dependence and the magnitude of of volborthite are found to be very similar to those of Ca kapellasite, despite of about an order of magnitude difference in We find that of both compounds is well reproduced, both qualitatively and quantitatively, by spin excitations described by the Schwinger-boson mean-field theory applied to KHA with the Dzyaloshinskii?Moriya interaction. This excellent agreement demonstrates not only that the thermal Hall effect in these kagom antiferromagnets is caused by spins in the spin liquid phase, but also that the elementary excitations of this spin liquid phase are well described by the bosonic spin excitations.
• Anomalous Transport Properties in BiS2-based Superconductors LnO1-xFxBiS2(Ln=Nd,La-Sm)

  Sho Iwasaki, Yoshiki Kawai, Shotaro Takahashi, Takaya Suda, Ying Wang, Yasunori Koshino, Fumiya Ogura, Yoshiyuki Shibayama, Tohru Kurosawa, Migaku Oda, Masayuki Ido, Naoki Momono

  Journal of the Physical Society of Japan 88 4 2019年02月 [査読有り][通常論文]
   

  We report the electronic properties of the layered bismuth-based sulfide superconductors NdO1-xFxBiS2 (x = 0.25, 0.4, and 0.5) and La1-ySmyO0.5F0.5BiS2 (y = 0.1-0.7), which have been studied by investigation of their transport properties and X-ray diffraction. In the lightly carrier-doped NdO1-xFxBiS2 (x = 0.25 and 0.4) and La1-ySmyO0.5F0.5BiS2 (y = 0.3 and 0.4), the resistivity and Hall coefficient exhibit anomalous temperature dependences below T-CDW( )similar to 130 and 200 K, respectively, suggesting the formation of an energy gap on the Fermi surface associated with charge-density wave (CDW). In NdO1-xFxBiS2 (x = 0.25), the bond angles and bond lengths of the Bi-S pentahedron change their temperature dependences below similar to 200K, suggesting that a lattice instability related to the Bi-S pentahedron exists below similar to 200K, which is much higher than T-CDW. These results indicate that the lattice instability of the Bi-S pentahedron can trigger a CDW transition in the low-carrier region of BiS2 superconductors.
• Spin Thermal Hall Conductivity of a Kagome Antiferromagnet

  Doki, H, Akazawa, M, Lee, HY, Han, JH, Sugii, K, Shimozawa, M, Kawashima, N, Oda, M, Yoshida, H, Yamashita, M

  PHYSICAL REVIEW LETTERS 121 9 097203  2018年08月 [査読有り][通常論文]
   

  A clear thermal Hall signal (kappa(xy)) was observed in the spin-liquid phase of the S = 1/2 kagome antiferromagnet Ca kapellasite [CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O]. We found that kappa(xy) is well reproduced, both qualitatively and quantitatively, using the Schwinger-boson mean-field theory with the Dzyaloshinskii-Moriya interaction of D/J similar to 0.1. In particular,kappa(xy) values of Ca kapellasite and those of another kagome antiferromagnet, volborthite, converge to one single curve in simulations modeled using Schwinger bosons, indicating a common temperature dependence of kappa(xy) for the spins of a kagome antiferromagnet.
• STM/STS study on electronic superstructures in the superconducting state of high-Tc cuprate Bi2Sr2CaCu2O8+δ

  S Mizuta, T Kurosawa, K Takeyama, N Momono, Y Ishii, H Yoshida, M Oda, M Ido

  Journal of Physics: Conf. Series 969 1 12071/1 - 12071/6 2018年04月19日 [査読有り][通常論文]
   

  We report STM/STS measurements at 8 K in underdoped Bi2Sr2CaCu2O8+δ crystals (T c = 76 K and hole-doping level p ∼ 0.12) whose energy spectra around the Fermi level are characterized by a two-gap structure consisting of spatially inhomogeneous pseudogap (PG) and comparatively homogeneous superconducting gap (SCG). Two electronic superstructures, checkerboard modulation (CBM) and Cu-O-Cu bond-centered modulation (BCM), are observed with mapping spectral weights at low energies within the SCG and the ratio of spectral weights at ±ΔPG (PG energy), respectively. On the basis of the present findings, we suggest that the lower-energy scale CBM is an intrinsic property of Cu-O planes and can coexist with the BCM whose characteristic energy is ∼ΔPG in identical regions in real space.
• Direct observation of orbital hybridisation in a cuprate superconductor

  Matt, CE, Sutter, D, Cook, AM, Sassa, Y, Mansson, M, Tjernberg, O, Das, L, Horio, M, Destraz, D, Fatuzzo, CG, Hauser, K, Shi, M, Kobayashi, M, Strocov, VN, Schmitt, T, Dudin, P, Hoesch, M, Pyon, S, Takayama, T, Takagi, H, Lipscombe, OJ, Hayden, SM, Kurosawa, T, Momono, N, Oda, M, Neupert, T, Chang, J

  NATURE COMMUNICATIONS 9 972  2018年03月 [査読有り][通常論文]
  
• Nonequilibrium quasiparticle dynamics in Bi-based superconductors measured by modulation photoexcitation spectroscopy

  Y. Toda, H. Mochizuki, S. Tsuchiya, T. Kurosawa, M. Oda, T. Mertelj, D. Mihailovic

  Journal of Superconductivity and Novel Magnetism 31 3 753 - 756 2018年 [査読有り][通常論文]
   

  We develop an orbital angular momentum (OAM) excitation pump-probe (Pp) spectroscopy and perform experiments on a Bi2 Sr2 CaCu2 O8+δ (Bi2212) superconductor. The OAM modulation for the pump is realized by using a transverse mode conversion technique which allows to modulate the chirality of the optical OAM with a fixed polarization. The result reveals a difference of the OAM-dependent transient reflectivity changes below Tc, indicating that the pump OAM can break the chiral symmetry of the superconducting (SC) state. The OAM dependences of the transient signal imply that the quasiparticle (QP) excitation with OAM enhances the SC with opposite chirality and/or suppress the SC with equal chirality. The temperature dependence of the OAM dynamics shows virtually no pairing fluctuation that usually appears in the QP dynamics observed by conventional Pp, suggesting that the nonequilibrium OAM dynamics is sensitive to the delocalized OAM associated with long range order.
• Gapless magnetic excitations in the kagome antiferromagnet Ca-kapellasite probed by Cl-35 NMR spectroscopy

  Y. Ihara, T. Sasaki, N. Noguchi, Y. Ishii, M. Oda, H. Yoshida

  PHYSICAL REVIEW B 96 18 180409  2017年11月 [査読有り][通常論文]
   

  The low-energy magnetic excitations of the spin-1/2 kagome antiferromagnet CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O (Ca-kapellasite) have been investigated by a Cl-35 NMR experiment in fields up to 18.9 T. Recently, Ca-kapellasite was found to be one of the most promising candidates to explore the intrinsic magnetic properties in kagome antiferromagnets, because magnetic defects, which deteriorate the intrinsic magnetic properties, are minimized by choosing Ca ions with a large ionic radius as the counterions. From our nuclear spin-lattice relaxation rate 1/T-1 measurement, we found a power-law temperature dependence below the magnetic ordering temperature T-M = 7.2 K, which leads us to suggest that gapless magnetic excitations survive even in the ordered state. This power-law behavior is suppressed in high magnetic fields. We discuss a possible magnetic state that can generate gapless excitations at low fields.
• Dynamics of superconducting order parameter through ultrafast normal-to-superconducting phase transition in Bi2Sr2CaCu2O8+delta from multipulse polarization-resolved transient optical reflectivity

  I. Madan, V. V. Baranov, Y. Toda, M. Oda, T. Kurosawa, V. V. Kabanov, T. Mertelj, D. Mihailovic

  PHYSICAL REVIEW B 96 18 184522  2017年11月 [査読有り][通常論文]
   

  A systematic temperature-dependent study of the femtosecond optical superconducting (SC) state destruction and recovery in Bi2Sr2CaCu2O8+delta cuprate superconductor by means of the all-optical polarization-sensitive multipulse spectroscopy is presented. At low temperatures and a partial SC state suppression, an anisotropic SC-gap recovery time scale is suggested by the data. The SC state destruction and recovery dynamics are compared to the recent TR-ARPES-inferred SC-gap dynamics and a qualitative agreement is found. Using a phenomenological response function, the experimental data are also compared to time-dependent Ginzburg-Landau model simulations.
• 1/8 Anomaly Induced by the Substitution of Dy in Underdoped Bi2Sr2Ca1-xDyxCu2O8+delta

  K. Kawamura, Y. Kobayashi, C. Kobashi, S. Baar, T. Kurosawa, M. Oda, M. Ido, N. Momono

  JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 30 8 2037 - 2042 2017年08月 [査読有り][通常論文]
   

  An anomalous "dip" feature near the hole concentration of p similar to 1/8 on the T-c - p curve of Bi2Sr2 Ca1- xDyxCu2O8+delta (Dy-Bi2212) was reported. Dy-Bi2212 with p similar to 1/8 exhibited a "checkerboard charge order" with a wave vector similar to 0.3 r.l.u., and well-defined coherent peaks were not observed in the quasiparticle tunneling spectra of this material, obtained from scanning tunneling microscopy/spectroscopy (STM/STS) experiments. The dip of the T-c - p curve induced by the substitution of Dy in Bi2212 was similar to that observed in Zn-doped Bi2212 (Akoshima et al., Phys. Rev. B 57, 7491 1998), suggesting that the suppression of Tc near p similar to 1/8 in Dy-Bi2212 is related to the pinning of the charge order.
• Rotation symmetry breaking in La2-xSrxCuO4 revealed by angle-resolved photoemission spectroscopy

  E. Razzoli, C. E. Matt, Y. Sassa, M. Mansson, O. Tjernberg, G. Drachuck, M. Monomo, M. Oda, T. Kurosawa, Y. Huang, N. C. Plumb, M. Radovic, A. Keren, L. Patthey, J. Mesot, M. Shi

  PHYSICAL REVIEW B 95 22 224504  2017年06月 [査読有り][通常論文]
   

  Using angle-resolved photoemission spectroscopy it is revealed that in the vicinity of optimal doping the electronic structure of La2-x SrxCuO4 cuprate undergoes an electronic reconstruction associated with a wave vector q(a) = (pi, 0). The reconstructed Fermi surface and folded band are distinct to the shadow bands observed in BSCCO cuprates and in underdoped La2-xSrxCuO4 with x <= 0.12, which shift the primary band along the zone diagonal direction. Furthermore, the folded bands appear only with q(a) = (pi, 0) vector, but not with q(b) = (0, pi). We demonstrate that the absence of q(b) reconstruction is not due to thematrix-element effects in the photoemission process, which indicates the fourfold symmetry is broken in the system.
• Damped spin excitations in a doped cuprate superconductor with orbital hybridization

  O. Ivashko, N. E. Shaik, X. Lu, C. G. Fatuzzo, M. Dantz, P. G. Freeman, D. E. McNally, D. Destraz, N. B. Christensen, T. Kurosawa, N. Momono, M. Oda, C. E. Matt, C. Monney, H. M. Ronnow, T. Schmitt, J. Chang

  PHYSICAL REVIEW B 95 21 214508  2017年06月 [査読有り][通常論文]
   

  A resonant inelastic x-ray scattering study of overdamped spin excitations in slightly underdoped La2-xSrxCuO4 (LSCO) with x = 0.12 and 0.145 is presented. Three high-symmetry directions have been investigated: (1) the antinodal (0,0) -> (1/2,0), (2) the nodal (0,0) -> (1/4, 1/4), and (3) the zone-boundary direction (1/2,0) -> (1/4, 1/4) connecting these two. The overdamped excitations exhibit strong dispersions along (1) and (3), whereas a much more modest dispersion is found along (2). This is in strong contrast to the undoped compound La2CuO4 (LCO) for which the strongest dispersions are found along (1) and (2). The t - t' - t'' - U Hubbard model used to explain the excitation spectrum of LCO predicts-for constant U/t-that the dispersion along (3) scales with (t'/ t)(2). However, the diagonal hopping t' extracted on LSCO using single-band models is low (t'/t similar to -0.16) and decreasing with doping. We therefore invoked a two-orbital (d(x2-y2) and dz(2)) model which implies that t' is enhanced. This effect acts to enhance the zone-boundary dispersion within the Hubbard model. We thus conclude that hybridization of d(x2-y2) and d(z)(2) states has a significant impact on the zone-boundary dispersion in LSCO.
• Unusual Magnetic State with Dual Magnetic Excitations in the Single Crystal of S=1/2 Kagome Lattice Antiferromagnet CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O

  Hiroyuki Yoshida, Naoya Noguchi, Yoshitaka Matsushita, Yuto Ishii, Yoshihiko Ihara, Migaku Oda, Hirotaka Okabe, Satoshi Yamashita, Yasuhiro Nakazawa, Atsushi Takata, Takanori Kida, Yasuo Narumi, Masayuki Hagiwara

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 86 3 033704  2017年03月 [査読有り][通常論文]
   

  We have succeeded in preparing single crystals of CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O, a candidate for the S = 1/2 Kagome lattice antiferromagnet. Magnetic properties of the compound are dominated by the nearest neighbor antiferromagnetic interaction J(1), and the next nearest neighbor ferromagnetic J(2) and an antiferromagnetic J(d) across a hexagon, which is different from related compounds Kapellasite and Haydeeite with ferromagnetic J(1). Magnetic susceptibility exhibits a sudden increase below 13K and a cusp anomaly at T* = 7.2K in the ab-plane, whereas only a moderate enhancement is observed below T* along the c-axis. A tiny peak detected in heat capacity at T* indicates the occurrence of a magnetic phase transition. The low temperature magnetic heat capacity was reproduced by assuming a two-dimensional spin-wave component and a temperature-linear term. The spin-wave contribution suggests a magnon excitation in a short-range ordered region, whereas the relatively large T-linear term 5.9 mJ/(Cu-mol center dot K-2) at H = 0T of this insulating compound suggests the existence of an unusual quasi-particle excitation below T*. They apparently reveal the unconventionality of the ground state of this S = 1/2 Kagome lattice antiferromagnet.
• Structural study of quasi-one-dimensional vanadium pyroxene LiVSi2O6 single crystals

  Yuto Ishii, Yoshitaka Matsushita, Migaku Oda, Hiroyuki Yoshida

  JOURNAL OF SOLID STATE CHEMISTRY 246 125 - 129 2017年02月 [査読有り][通常論文]
   

  Single crystals of quasi-one-dimensional vanadium pyroxene LiVSi2O6 were synthesized and the crystal structures at 293 K and 113 K were studied using X-ray diffraction experiments. We found a structural phase transition from the room-temperature crystal structure with space group C2/c to a low-temperature structure with space group P2(I)/c, resulting from a rotational displacement of SiO4 tetrahedra. The temperature dependence of magnetic susceptibility shows a broad maximum around 116 K, suggesting an opening of the Haldane gap expected for one-dimensional antiferromagnets with S=1. However, an antiferromagnetic long-range order was developed below 24 K, probably caused by a weak inter-chain magnetic coupling in the compound.
• Out-of-Plane Disorder Effects on the Energy Gaps and Electronic Charge Order in Bi2Sr1.7R0.3CuO6+delta (R = La and Eu)

  Tohru Kurosawa, Kohsaku Takeyama, Stefan Baar, Yuto Shibata, Moeko Kataoka, Shusei Mizuta, Hiroshi Yoshida, Naoki Momono, Migaku Oda, Masayuki Ido

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 85 4 044709  2016年04月 [査読有り][通常論文]
   

  We performed STM/STS experiments at 8K in Bi2Sr1.7R0.3CuO6+delta (R-Bi2201) systems that had optimal (OP) holedoping levels (similar to 0.17) but different T-c values, 35K for R = La and 20K for R = Eu, and examined out-of-plane disorder effects on the superconducting (SC) gap (SCG) and the pseudogap (PG) which is associated with the so-called "checkerboard charge order" (CCO). As out-of-plane disorders are strengthened by replacing La with Eu in OP R-Bi2201, the antinodal PG size Delta(PG) increases from similar to 30 to similar to 60 meV, the nodal SCG size Delta(SC) seems to decrease from similar to 7 to similar to 4 meV, and the pairing gap amplitude Delta(0) or d-wave gap size at the antinodes is almost unchanged (Delta(0) similar to 15 meV). These gap sizes for OP doping in Eu-Bi2201 are comparable to those for an underdoping level of similar to 0.1 in La-Bi2201. Although out-of-plane disorders strongly affect the electronic system of the Cu-O plane, they have no effect on the period of the CCO, which is five times the lattice constant (5a) along the Cu-O bond directions for OP doping and 4a for p similar to 0.1. We suggest that the concentration of holes doped into the Cu-O plane may be an essential factor for determining the period of the CCO.
• The Impurity Effects on the Superconducting Gap in the High-T-c Superconductor Bi2Sr2CaCu2-xFexO8+delta Investigated by STM/STS

  S. Baar, N. Momono, K. Kawamura, Y. Kobayashi, S. Iwasaki, T. Sakawaki, Y. Amakai, H. Takano, T. Kurosawa, M. Oda, M. Ido

  JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 29 3 659 - 662 2016年03月 [査読有り][通常論文]
   

  We performed scanning tunneling microscopy/ spectroscopy (STM/STS) experiments to investigate Fe substitution effects on the superconductivity (SC) of overdoped Bi2212. The gap-edge peaks in STS spectrum at Ta << T (c) become inhomogeneous strongly in Fe-doped Bi2212. The spectral weight around zero bias, namely the density of states (DOS) at similar to E (F) is partly recovered by substitution of Fe in every position. The recovery of the DOS at similar to E (F) can be explained in terms of impurity effects on d-wave SC in the unitarity limit. However, the strong inhomogeneity of gap-edge peaks would be ascribed to different effects due to Fe-substitution.
• 19aPS-75 S=5/2三角格子ダイマーCs_3Fe_2Cl_9の磁性

  石井 裕人, 野口 直彌, 吉田 紘行, 小田 研

  日本物理学会講演概要集 71 1081 - 1081 一般社団法人日本物理学会 2016年
• 19aPS-43 擬一次元量子スピン系CaCu_2(OH)_3Cl_3のスピン一重項状態

  野口 直彌, 石井 裕人, 吉田 紘行, 松下 能孝, 小田 研

  日本物理学会講演概要集 71 1050 - 1050 一般社団法人日本物理学会 2016年
• 銅酸化物高温超伝導体Bi₂Sr₂CaCu₂O_8+δの超伝導に対するDy添加効果

  河村 一磨, 小林 侑幹, 小橋 知沙登, Baar Stefan, 松元 和幸, 桃野 直樹, 黒澤 徹, 小田 研, 伊土 政幸

  日本物理学会講演概要集 71 1996 - 1996 一般社団法人 日本物理学会 2016年 

  !LaTeX 銅酸化物高温超伝導体Bi_2_Sr_2_CaCu_2_O_8+${\delta}$_(Bi2212)では，CaサイトのDy置換によりエネルギーギャップがd波からずれて大きくなることが報告されている．本研究では，このDy添加について知見を得る目的でBi_2_Sr_2_Ca_1-x_Dy_x_Cu_2_O_8+${\delta}$_単結晶を用いた磁化や熱電能の測定，走査トンネル顕微鏡を用いた実験を行った．

• STM/STSから見たBi2212の電荷秩序とエネルギーギャップ

  水田 崇聖, 岸 文香, 米川 雄太, 黒沢 徹, 桃野 直樹, 竹山 幸作, 吉田 紘行, 小田 研, 伊土 政幸

  日本物理学会講演概要集 71 1993 - 1993 一般社団法人 日本物理学会 2016年 

  銅酸化物高温超伝導体Bi2212のアンダードープ試料においてSTM/STS実験を行い、この系で問題となっている電荷秩序が観測されるエネルギー領域（電子的な準粒子状態に対応する正の適当なエネルギー領域でのみ観測されるか？）について調べた。また、このエネルギー領域と超伝導ギャップや擬ギャップとの関係についても調べた。講演では、これらの結果について報告する。

• BiS₂系超伝導体LaO_1-xF_xBi_1-ySb_yS₂におけるSb置換効果

  坂脇 卓磨, 岩嵜 翔, 河合 祥紀, 黒澤 徹, 小田 研, 伊土 政幸, 雨海 有佑, 高野 英明, 桃野 直樹

  日本物理学会講演概要集 71 2191 - 2191 一般社団法人 日本物理学会 2016年 

  典型的な層状硫化物超伝導体の1つであるLaO_1-x_F_x_BiS_2_の超伝導転移温度T_c_はFのドープ量に依存し、x = 0.5(最適ドープ)で最も高くT_c_〜2.7 Kとなる。興味深いことにT_c_は高圧合成あるいは圧力印加で10.6 Kまで大きく上昇する。本研究では常圧下合成において、幅広い組成のLaO_1-x_F_x_BiS_2_、及びBiサイトをSbで部分置換したLaO_1-x_F_x_Bi_1-y_Sb_y_S_2_の単結晶を作製し、超伝導に対するSbの置換効果を調べた。当日はそれらの結果について報告する。

• BiS₂系超伝導体LnO_1-xF_xBiS₂(Ln=La,Nd)の超伝導と輸送特性

  岩嵜 翔, 坂脇 卓磨, 高橋 将太郎, 黒澤 徹, 小田 研, 伊土 政幸, 雨海 有佑, 高野 英明, 桃野 直樹

  日本物理学会講演概要集 71 2190 - 2190 一般社団法人 日本物理学会 2016年 

  典型的なBiS_2_系超伝導体LnO_1-x_F_x_BiS_2_(Ln=La,Ce,Pr,Nd)はO^2-^をF^-^で置換することにより電子が伝導層にドープされ超伝導が発現し、超伝導転移温度T_c_はF濃度に依存する。LaO_1-x_F_x_BiS_2_(La系)とNdO_1-x_F_x_BiS_2_(Nd系)はxに対するT_c_カーブが異なっており、T_c_のピーク位置にズレが生じている。本研究ではLa系とNd系に注目し、F置換による超伝導や電子系の変化を輸送特性から調べ、La系とNd系における超伝導や電子系の特徴について知見を得ることを目的とした。

• 銅酸化物超伝導体Bi₂Sr_2-xLn_xCuO_6+δ(Ln=La, Nd, Eu)の超伝導に対するSrサイト置換効果

  小林 侑幹, 河村 一磨, Baar Stefan, 開米 望, 桃野 直樹, 松元 和幸, 黒澤 徹, 小田 研, 伊土 政幸

  日本物理学会講演概要集 71 1918 - 1918 一般社団法人 日本物理学会 2016年 

  銅酸化物超伝導体Bi_2_Sr_2_CuO_6+!LaTeX$\d$_はCu-O面の上下にあるSr-O面にSrとイオン半径が大きく異なる希土類元素Lnを添加すると超伝導転移温度T_c_が大きく抑制されることが報告されている。近年、ARPESやSTM/STSからこのような面間のdisorderの効果が調べられ、面間disorderの増強に伴いアンチノード付近のギャップの発達が顕著になると報告されている。本研究ではBi_2_Sr_2-x_Ln_x_CuO_6+!LaTeX$\d$_(Ln=La, Nd, Eu)において面間disorderが超伝導に及ぶす影響について主にSTM/STSから調べたので報告する。

• Time-resolved polarimetry for photoexcited QP dynamics in Bi2212

  K. Watanabe, S. Tsuchiya, Y. Toda, T. Kurosawa, M. Oda, T. Mertelj, I. Madan, V. V. Kabanov, D. Mihailovic

  INTERNATIONAL JOURNAL OF MODERN PHYSICS B 29 25-26 1542031  2015年10月 [査読有り][通常論文]
   

  The dynamics of quasi-particle (QP) excitations with different symmetry is investigated in the superconducting (SC) and pseudogap (PG) states of the high-temperature superconductor Bi2Sr2CaCu2O8+d (Bi2212) using a polarization-sensitive optical pump-probe measurement. The observation of distinct anisotropies for SC excitations and for PG excitations by the probe beam polarization and absence of any dependence on the pump beam polarization evidence the existence of a spontaneous spatial symmetry breaking in the PG state.
• Nodal gap behavior of Bi(2)Sr(2-x)Ln(x)CuO(6+delta) (Ln = La, Eu) investigated by specific heat measurements

  M. Shimizu, Y. Moriya, S. Baar, N. Momono, Y. Amakai, H. Takano, S. Murayama, T. Kurosawa, M. Oda, M. Ido

  INTERNATIONAL JOURNAL OF MODERN PHYSICS B 29 25-26 1542014  2015年10月 [査読有り][通常論文]
   

  We performed low-temperature specific heat measurements on slightly underdoped samples of monolayer cuprate superconductors Bi(2)Sr(2-x)Ln(x)CuO(6+delta) (Ln = La, Eu, Ln-Bi2201) under magnetic fields H. In La-Bi2201, the coefficient gamma of T-linear term in the electronic specific heat C-el at T << T-c shows root H dependence, as expected in d(x)(2)-y(2) -wave superconductors. In Eu-Bi2201, gamma shows almost the same root H dependence as that of La-Bi2201 below H similar to 2 T, while gamma is suppressed above H similar to 2 T and deviates downward from the root H curve of La-Bi2201. This result suggests the the gap and the electronic excitation spectrum near nodes are modified in Eu-Bi2201 except the region of the Fermi surface in the immediate vicinity of nodes.
• STM/STS studies for interplane disorder effects on the electronic states of the Cu-O plane in Bi2201

  T. Kurosawa, G. Hatta, H. Miyazaki, J. Yamaji, K. Yoshikawa, Y. Nakagawa, Y. Shibata, H. Yoshida, M. Oda, M. Ido, K. Takeyama, N. Momono

  INTERNATIONAL JOURNAL OF MODERN PHYSICS B 29 25-26 1542009  2015年10月 [査読有り][通常論文]
   

  STM/STS experiments have been performed in Bi2Sr1.7R0.3CuO6+delta (R-Bi2201) systems with R = La and Eu, which are of a nearly optimal doping level p(o) but have different T-c values, 35 K and 20 K, respectively, to examine interplane disorder effects on the superconducting (SC) gap and the pseudogap (PG) that is accompanied by a checkerboard-type charge order (CCO). We report that as interplane disorders are strengthened by replacing La with Eu in optimal Bi2201, the antinodal PG size Delta* increases from similar to 30 meV to similar to 60 meV, which is comparable to the value for an under-doping level p/p(o) similar to 0.5 in La-Bi2201. On the other hand, the period of CCO in optimal Eu-Bi2201 is the same as in optimal La-Bi2201, about five times lattice constant similar to 5a along the Cu-O bond directions; it remains unchanged even if the PG develops markedly to the same degree as for p/p(o) similar to 0.5 in La-Bi2201, whose period is similar to 4a.
• Electron scattering, charge order, and pseudogap physics in La1.6-xNd0.4SrxCuO4: An angle-resolved photoemission spectroscopy study

  C. E. Matt, C. G. Fatuzzo, Y. Sassa, M. Mansson, S. Fatale, V. Bitetta, X. Shi, S. Pailhes, M. H. Berntsen, T. Kurosawa, M. Oda, N. Momono, O. J. Lipscombe, S. M. Hayden, J. -Q. Yan, J. -S. Zhou, J. B. Goodenough, S. Pyon, T. Takayama, H. Takagi, L. Patthey, A. Bendounan, E. Razzoli, M. Shi, N. C. Plumb, M. Radovic, M. Grioni, J. Mesot, O. Tjernberg, J. Chang

  PHYSICAL REVIEW B 92 13 134524  2015年10月 [査読有り][通常論文]
   

  We report an angle-resolved photoemission study of the charge stripe ordered La1.6-xNd0.4SrxCuO4 (Nd-LSCO) system. A comparative and quantitative line-shape analysis is presented as the system evolves from the overdoped regime into the charge ordered phase. On the overdoped side (x = 0.20), a normal-state antinodal spectral gap opens upon cooling below 80 K. In this process, spectral weight is preserved but redistributed to larger energies. A correlation between this spectral gap and electron scattering is found. A different line shape is observed in the antinodal region of charge ordered Nd-LSCO x = 1/8. Significant low-energy spectral weight appears to be lost. These observations are discussed in terms of spectral-weight redistribution and gapping originating from charge stripe ordering.
• Field-induced interplanar magnetic correlations in the high-temperature superconductor La1.88Sr0.12CuO4

  A. T. Romer, P. J. Ray, H. Jacobsen, L. Udby, B. M. Andersen, M. Bertelsen, S. L. Holm, N. B. Christensen, R. Toft-Petersen, M. Skoulatos, M. Laver, A. Schneidewind, P. Link, M. Oda, M. Ido, N. Momono, K. Lefmann

  PHYSICAL REVIEW B 91 17 174507  2015年05月 [査読有り][通常論文]
   

  We present neutron-scattering studies of the interplanar magnetic correlations in the high-temperature superconductor La1.88Sr0.12CuO4 (T-c = 27 K). The correlations are studied both in a magnetic field applied perpendicular to the CuO2 planes, and in zero field under different cooling conditions. We find that the effect of the magnetic field is to increase the magnetic scattering signal at all values of the out-of-plane wave vector L, indicating an overall increase of the magnetic moments. In addition, weak correlations between the copper oxide planes develop in the presence of a magnetic field. This effect is not taken into account in previous reports on the field effect of magnetic scattering, since usually only L approximate to 0 is probed. Interestingly, the results of quench-cooling the sample are similar to those obtained by applying a magnetic field. Finally, a small variation of the incommensurate peak position as a function of L provides evidence that the incommensurate signal is twinned with the magnetic scattering from the dominant and subdominant structural twin displaying peaks at even and odd values of L, respectively, in our crystal.
• Evidence for carrier localization in the pseudogap state of cuprate superconductors from coherent quench experiments

  I. Madan, T. Kurosawa, Y. Toda, M. Oda, T. Mertelj, D. Mihailovic

  NATURE COMMUNICATIONS 6 6958  2015年04月 [査読有り][通常論文]
   

  A 'pseudogap' was introduced by Mott to describe a state of matter that has a minimum in the density of states at the Fermi level, deep enough for states to become localized. It can arise either from Coulomb repulsion between electrons, and/or incipient charge or spin order. Here we employ ultrafast spectroscopy to study dynamical properties of the normal to pseudogap state transition in the prototype high-temperature superconductor Bi2Sr2CaCu2O8+delta. We perform a systematic temperature and doping dependence study of the pseudogap photodestruction and recovery in coherent quench experiments, revealing marked absence of critical behaviour of the elementary excitations, which implies an absence of collective electronic ordering beyond a few coherence lengths on short timescales. The data imply ultrafast carrier localization into a textured polaronic state arising from a competing Coulomb interaction and lattice strain, enhanced by a Fermi surface instability.
• STM/STS study of the superconducting gap in SmFeAsO1-xFx

  Yuki Kawashima, Koichi Ichimura, Kazuhiro Katono, Tohru Kurosawa, Migaku Oda, Satoshi Tanda, Yoichi Kamihara, Hideo Hosono

  SOLID STATE COMMUNICATIONS 204 33 - 36 2015年02月 [査読有り][通常論文]
   

  We report an electron tunneling study of SmFeAsO1-xFx in the low doping region (x=0, 0.045, 0.046, 0.069) by low temperature UI-IV-STM/STS. Superconducting gaps are observed for each superconducting sample x=0.045 (T-c=12.9 K), x=0.046 (T-c=32.9 K) and x=0.069 (T-c=46.9 K). We obtained corresponding superconducting gap size of Delta(sc) = 9.5 +/- 0.5 meV, 9.75 +/- 0.25 mcV and 11 +/- 1 meV. While T-c increases, Delta(sc) is kept the same. This suggests that the effective attractive interaction is the same and that there is some mechanism that suppresses the superconductivity in the low doping region. On the other hand, similar gap structures were found in a non superconducting sample with x=0 at 7.8 K. The obtained gap size was Delta(N) = 8.5 +/- 1.5 meV, which is almost the same as the superconducting gap in the superconducting samples (x=0.045, 0.046, 0.069). (C) 2014 Published by Elsevier Ltd.
• 19aPS-16 STM/STSから見たBi_2Sr_2CaCu_2O_<8+δ>におけるFe置換効果

  鈴木 順也, 河村 一磨, 小林 侑幹, 桃野 直樹, 雨海 有佑, 高野 英明, 黒澤 徹, 小田 研, 伊土 政幸

  日本物理学会講演概要集 70 2110 - 2110 一般社団法人日本物理学会 2015年
• 19aPS-17 STM/STSから見たBi_2Sr_2Ca_<1-x>Dy_xCu_2O_<8+δ>のギャップ構造

  曽田 純平, 河村 一磨, 桃野 直樹, 雨海 有佑, 高野 英明, 黒澤 徹, 小田 研, 伊土 政幸

  日本物理学会講演概要集 70 2111 - 2111 一般社団法人日本物理学会 2015年
• 18aCG-5 新奇スピン1/2 カゴメ格子反強磁性体CaCu_3(OH)_6Cl_2・0.67H_2O の磁性

  野口 直彌, 石井 裕人, 片岡 萌子, 吉田 紘行, 松下 能孝, 小田 研

  日本物理学会講演概要集 70 911 - 911 一般社団法人日本物理学会 2015年
• 18aCG-7 S = 3/2 カゴメ格子反強磁性体 Li_2Cr_3SbO_8 の磁性

  石井 裕人, 野口 直彌, 片岡 萌子, 吉田 紘行, 山浦 一成, 宮川 仁, 小田 研

  日本物理学会講演概要集 70 913 - 913 一般社団法人日本物理学会 2015年
• 24pDC-4 STM/STSから見たBi2212のオーバードープ領域におけるギャップ構造

  岸 文香, 米川 雄太, 黒澤 徹, 桃野 直樹, 竹山 幸作, 吉田 紘行, 小田 研, 伊土 政幸

  日本物理学会講演概要集 70 2484 - 2484 一般社団法人日本物理学会 2015年
• 24pDC-3 STM/STSから見たアンダードープ領域におけるBi2212の電荷秩序と準粒子干渉

  米川 雄太, 板垣 征一朗, 岸 文香, 黒澤 徹, 桃野 直樹, 吉田 紘行, 竹山 幸作, 小田 研, 伊土 政幸

  日本物理学会講演概要集 70 2483 - 2483 一般社団法人日本物理学会 2015年
• Impurity Effects on the Energy Gap in Fe-doped Bi2212

  Stefan Baar, N. Momono, J. Suzuki, J. Soda, K. Kobayashi, H. Takano, Y. Amakai, T. Kurosawa, M. Oda, M. Ido

  20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015 75 18 - 22 2015年 [査読有り][通常論文]
   

  We performed scanning tunnelling microscopy/spectroscopy (STM/STS) on Fe-doped Bi2212. The Fe substitution for Cu causes a strong spatial inhomogeneity in STS spectra. The energy gap (Delta(1) similar to 80mV) has a sub-gap (Delta(2) similar to 70mV) in some distinct locations on the sample surface. We find that the gap edge peaks are largely depressed and only the sub-gap survives across the region where the spatial modulation of the local density of states is stronger. This indicates, that Delta(1) anti-correlates with Delta(2).
• Rotated stripe order and its competition with superconductivity in La1.88 Sr0.12 CuO4

  V. Thampy, M. P.M. Dean, N. B. Christensen, L. Steinke, Z. Islam, M. Oda, M. Ido, N. Momono, S. B. Wilkins, J. P. Hill

  Physical Review B - Condensed Matter and Materials Physics 90 10 2014年09月26日 [査読有り][通常論文]
   

  We report the observation of a bulk charge modulation in La1.88Sr0.12CuO4 (LSCO) with a characteristic in-plane wave vector of (0.236,±δ), with δ=0.011 r.l.u. The transverse shift of the ordering wave vector indicates the presence of rotated charge-stripe ordering, demonstrating that the charge ordering is not pinned to the Cu-O bond direction. On cooling through the superconducting transition, we find an abrupt change in the growth of the charge correlations and a suppression of the charge order parameter indicating competition between the two orderings. Orthorhombic LSCO thus helps bridge the apparent disparities between the behavior previously observed in the tetragonal "214" cuprates and the orthorhombic yttrium and bismuth-based cuprates and thus lends strong support to the idea that there is a common motif to charge order in all cuprate families.
• Rotational symmetry breaking in Bi2Sr2CaCu2O8+delta probed by polarized femtosecond spectroscopy

  Y. Toda, F. Kawanokami, T. Kurosawa, M. Oda, I. Madan, T. Mertelj, V. V. Kabanov, D. Mihailovic

  PHYSICAL REVIEW B 90 9 094513  2014年09月 [査読有り][通常論文]
   

  The quasiparticle (QP) dynamics with different symmetry is investigated in the superconducting (SC) and normal state of the high-temperature superconductor Bi2Sr2CaCu2O8+delta (Bi2212) using optical pump-probe experiments with different light polarizations at different doping levels. The observation of distinct selection rules for SC excitations present in A(1g) and B-1g symmetries, and for the pseudogap (PG) excitations present in A(1g) and B-2g symmetries by the probe, and absence of any dependence on the pump beam polarization leads to the unequivocal conclusion of the existence of a spontaneous spatial symmetry breaking in the PG state not limited to the sample surface.
• Rotated stripe order and its competition with superconductivity in La1.88Sr0.12CuO4

  V. Thampy, M. P. M. Dean, N. B. Christensen, L. Steinke, Z. Islam, M. Oda, M. Ido, N. Momono, S. B. Wilkins, J. P. Hill

  PHYSICAL REVIEW B 90 10 Thampy, V; Dean, MPM; Christen  2014年09月 [査読有り][通常論文]
   

  We report the observation of a bulk charge modulation in La1.88Sr0.12CuO4 (LSCO) with a characteristic in-plane wave vector of (0.236, +/-delta), with delta = 0.011 r.l.u. The transverse shift of the ordering wave vector indicates the presence of rotated charge-stripe ordering, demonstrating that the charge ordering is not pinned to the Cu-O bond direction. On cooling through the superconducting transition, we find an abrupt change in the growth of the charge correlations and a suppression of the charge order parameter indicating competition between the two orderings. Orthorhombic LSCO thus helps bridge the apparent disparities between the behavior previously observed in the tetragonal "214" cuprates and the orthorhombic yttrium and bismuth-based cuprates and thus lends strong support to the idea that there is a common motif to charge order in all cuprate families.
• Separating pairing from quantum phase coherence dynamics above the superconducting transition by femtosecond spectroscopy

  I. Madan, T. Kurosawa, Y. Toda, M. Oda, T. Mertelj, P. Kusar, D. Mihailovic

  SCIENTIFIC REPORTS 4 5656  2014年07月 [査読有り][通常論文]
   

  In classical superconductors an energy gap and phase coherence appear simultaneously with pairing at the transition to the superconducting state. In high-temperature superconductors, the possibility that pairing and phase coherence are distinct and independent processes has led to intense experimental search of their separate manifestations. Using femtosecond spectroscopy methods we now show that it is possible to clearly separate fluctuation dynamics of the superconducting pairing amplitude from the phase relaxation above the critical transition temperature. Empirically establishing a close correspondence between the superfluid density measured by THz spectroscopy and superconducting optical pump-probe response over a wide region of temperature, we find that in differently doped Bi2Sr2CaCu2O8+delta crystals the pairing gap amplitude monotonically extends well beyond T-c, while the phase coherence shows a pronounced power-law divergence as T -> T-c, thus showing that phase coherence and gap formation are distinct processes which occur on different timescales.
• Strain-Induced Enhancement of the Electron Energy Relaxation in Strongly Correlated Superconductors

  C. Gadermaier, V. V. Kabanov, A. S. Alexandrov, L. Stojchevska, T. Mertelj, C. Manzoni, G. Cerullo, N. D. Zhigadlo, J. Karpinski, Y. Q. Cai, X. Yao, Y. Toda, M. Oda, S. Sugai, D. Mihailovic

  PHYSICAL REVIEW X 4 1 011056  2014年03月 [査読有り][通常論文]
   

  We use femtosecond optical spectroscopy to systematically measure the primary energy relaxation rate Gamma(1) of photoexcited carriers in cuprate and pnictide superconductors. We find that Gamma(1) increases monotonically with increased negative strain in the crystallographic a axis. Generally, the Bardeen-Shockley deformation potential theorem and, specifically, pressure-induced Raman shifts reported in the literature suggest that increased negative strain enhances electron-phonon coupling, which implies that the observed direct correspondence between a and Gamma(1) is consistent with the canonical assignment of Gamma(1) to the electron-phonon interaction. The well-known nonmonotonic dependence of the superconducting critical temperature T-c on the a-axis strain is also reflected in a systematic dependence T-c on Gamma(1), with a distinct maximum at intermediate values (similar to 16 ps(-1) at room temperature). The empirical nonmonotonic systematic variation of T-c with the strength of the electron-phonon interaction provides us with unique insight into the role of electron-phonon interaction in relation to the mechanism of high-T-c superconductivity as a crossover phenomenon.
• Impact of pseudogap on photoinduced superconducting phase transition in underdoped Bi2212

  Y. Toda, T. Mertelj, P. Kusar, T. Kurosawa, M. Oda, M. Ido, D. Mihailovic

  PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 493 112 - 113 2013年10月 [査読有り][通常論文]
   

  We report nonequilibrium quasiparticle (QP) dynamics in underdoped Bi2212 crystals using ultrafast optical spectroscopy, which allows to analyze the dynamics associated with the superconducting (SC) and psuedogap (PG) QPs independently. In the saturation condition of the SC component, where the SC condensate is fully destroyed within the photoexcited volume, we found a delay of the SC state recovery associated with a transient normal state. The delay increases linearly with increasing the pump fluence. The QP dynamics also shows a contribution of the PG component, whose magnitude at the start of the SC state recovery was almost constant at various pump fluences, suggesting a critical level of PG order before the SC condensate can recover. (C) 2013 Elsevier B.V. All rights reserved.
• Charge stripe structure in Fe1+xTe by STM

  Yuki Kawashima, Koichi Ichimura, Junya Ishioka, Tohru Kurosawa, Migaku Oda, Kazuhiko Yamaya, Satoshi Tanda

  SOLID STATE COMMUNICATIONS 167 10 - 13 2013年08月 [査読有り][通常論文]
   

  The electronic state of Fe1.17Te was investigated with atomic resolution by using STM. We discovered a charge stripe structure at 7.8 K for the first time. The wave vector of the charge stripe structure is along the a-axis or b-axis. Furthermore we found that the charge stripe occurred at the Fe layer. We also found a 9 meV gap structure on the Fermi surface by STS. The gap size is consistent with the mean field approximation with SOW transition temperature of 58 K. (C) 2013 Elsevier Ltd. All rights reserved.
• Glassy low-energy spin fluctuations and anisotropy gap in La1.88Sr0.12CuO4

  A. T. Romer, J. Chang, N. B. Christensen, B. M. Andersen, K. Lefmann, L. Maehler, J. Gavilano, R. Gilardi, Ch. Niedermayer, H. M. Ronnow, A. Schneidewind, P. Link, M. Oda, M. Ido, N. Momono, J. Mesot

  PHYSICAL REVIEW B 87 14 144513  2013年04月 [査読有り][通常論文]
   

  We present high-resolution triple-axis neutron scattering studies of the high-temperature superconductor La1.88Sr0.12CuO4 (T-c = 27 K). The temperature dependence of the low-energy incommensurate magnetic fluctuations reveals distinctly glassy features. The glassiness is confirmed by the difference between the ordering temperature T-N similar or equal to T-c inferred from elastic neutron scattering and the freezing temperature T-f similar or equal to 11 K obtained from muon spin rotation studies. The magnetic field independence of the observed excitation spectrum as well as the observation of a partial suppression of magnetic spectral weight below 0.75 meV for temperatures smaller than T-f, indicate that the stripe frozen state is capable of supporting a spin anisotropy gap, of a magnitude similar to that observed in the spin and charge stripe-ordered ground state of La1.875Ba0.125CuO4. The difference between T-N and T-f implies that the significant enhancement in a magnetic field of nominally elastic incommensurate scattering is caused by strictly inelastic scattering-at least in the temperature range between T-f and T-c-which is not resolved in the present experiment. Combining the results obtained from our study of La1.88Sr0.12CuO4 with a critical reappraisal of published neutron scattering work on samples with chemical composition close to p = 0.12, where local probes indicate a sharp maximum in T-f (p), we arrive at the view that the low-energy fluctuations are strongly dependent on composition in this regime, with anisotropy gaps dominating only sufficiently close to p = 0.12 and superconducting spin gaps dominating elsewhere. DOI: 10.1103/PhysRevB.87.144513
• Charge stripe structure in FeTe

  Y. Kawashima, K. Ichimura, J. Ishioka, T. Kurosawa, M. Oda, K. Yamaya, S. Tanda

  PHYSICA B-CONDENSED MATTER 407 11 1796 - 1798 2012年06月 [査読有り][通常論文]
   

  We report the STM study on a single-crystalline sample of FeTe at 7.8 K. FeTe is one of the iron-based superconductor. We measured the resistivity and the magnetization of FeTe. FeTe shows SDW transition at 58 K on these measurements. We study the electronic state of FeTe by using STM/STS for observing FeTe from a microscopic viewpoint. We observed the iron layer and the tellurium layer with atomic resolution. Moreover, we discover the charge stripe structure on STM/STS measurement. We find the charge stripe structure is caused by iron atoms from the analysis. The gap structure of 9 meV was observed in tunneling spectra. This gap size is consistent with the SDW gap which is expected from mean field theory with T-N= 58 K. (C) 2012 Elsevier B.V. All rights reserved.
• High superconducting critical temperatures depend systematically on the electron-phonon interaction strength

  C. Gadermaier, V. V. Kabanov, A. S. Alexandrov, L. Stojchevska, T. Mertelj, C. Manzoni, G. Cerullo, N. D. Zhigadlo, J. Karpinski, Y. Q. Cai, X. Yao, Y. Toda, M. Oda, S. Sugai, D. Mihailovic

  2012年05月 [査読有り][通常論文]
   

  The origin of high critical temperature (Tc) superconductivity is still
  remarkably elusive. To gain insight into the high- Tc mechanism, we need
  experiments which identify the parameters that determine Tc and link them to
  the interaction(s) that establish the superconducting state. Here we show that
  for pnictides, cuprates, and bismuthates Tc depends systematically on the
  primary electron energy relaxation rate 1/tau_1. We find that 1/tau_1 is a
  direct experimental measure of the strength of the electron-phonon interaction
  (EPI) and correlates with structural parameters, in particular the l...
• Ni-impurity effects on the superconducting gap of La 2-xSr xCuO 4 studied from the magnetic field and temperature dependence of the electronic specific heat

  T. Kurosawa, N. Momono, M. Oda, M. Ido

  Physical Review B - Condensed Matter and Materials Physics 85 13 2012年04月23日 [査読有り][通常論文]
   

  The magnetic field and temperature dependence of the electronic specific heat C el have been systematically investigated in La 2-xSr xCu 1-yNi yO 4 (LSCNO) in order to study Ni-impurity effects on the superconducting (SC) gap. In LSCNO with x=0.15 and y=0.015, the value of γ (≡C el/T) at T=0 K, γ 0, is enhanced under the magnetic field H applied along the c axis. The increment of γ 0, Δγ 0, follows the Volovik relation Δγ 0=A√H, characteristic of the SC gap with line nodes, with prefactor A similar to that of a pure sample. The C el/T versus T curve under H=0 shows a d-wave-like SC anomaly with an abrupt increase at T c and T-linear dependence at TT c, although the γ 0-value in the C el/T versus T curve increases with increasing Ni concentrations. Interestingly, as the SC part of C el/T, C el/T- γ 0≡γ s, decreases in LSCNO, T c is reduced in proportion to the decrease of γ s. These findings can be explained phenomenologically by a simple model in which Ni impurities bring about strong pair breaking at the edges of the coherent nodal part of the Fermi surface but in the vicinity of the nodes of the SC gap. The reduction of the SC condensation energy U 0 in LSCNO, evaluated from C el at T≤T c, is also understood by the same model. © 2012 American Physical Society.
• Spin density wave induced disordering of the vortex lattice in superconducting La2-xSrxCuO4

  J. Chang, J. S. White, M. Laver, C. J. Bowell, S. P. Brown, A. T. Holmes, L. Maechler, S. Streassle, R. Gilardi, S. Gerber, T. Kurosawa, N. Momono, M. Oda, M. Ido, O. J. Lipscombe, S. M. Hayden, C. D. Dewhurst, R. Vavrin, J. Gavilano, J. Kohlbrecher, E. M. Forgan, J. Mesot

  PHYSICAL REVIEW B 85 13 134520  2012年04月 [査読有り][通常論文]
   

  We use small-angle neutron scattering to study the superconducting vortex lattice in La2-xSrxCuO4 as a function of doping and magnetic field. We show that near optimally doping the vortex lattice coordination and the superconducting coherence length. are controlled by a Van Hove singularity crossing the Fermi level near the Brillouin zone boundary. The vortex lattice properties change dramatically as a spin-density-wave instability is approached upon underdoping. The Bragg glass paradigm provides a good description of this regime and suggests that spin-density-wave order acts as a source of disorder on the vortex lattice.
• Ni-impurity effects on the superconducting gap of La2-xSrxCuO4 studied from the magnetic field and temperature dependence of the electronic specific heat

  T. Kurosawa, N. Momono, M. Oda, M. Ido

  PHYSICAL REVIEW B 85 13 134522  2012年04月 [査読有り][通常論文]
   

  The magnetic field and temperature dependence of the electronic specific heat C-el have been systematically investigated in La2-xSrxCu1-yNiyO4 (LSCNO) in order to study Ni-impurity effects on the superconducting (SC) gap. In LSCNO with x = 0.15 and y = 0.015, the value of gamma ( C-el/T) at T = 0 K, gamma(0), is enhanced under the magnetic field H applied along the c axis. The increment of gamma(0), Delta gamma(0), follows the Volovik relation Delta gamma(0) = A root H, characteristic of the SC gap with line nodes, with prefactor A similar to that of a pure sample. The C-el/T versus T curve under H = 0 shows a d-wave-like SC anomaly with an abrupt increase at T-c and T-linear dependence at T << T-c, although the gamma(0)-value in the C-el/T versus T curve increases with increasing Ni concentrations. Interestingly, as the SC part of C-el/T, C-el/T - gamma(0) gamma(s), decreases in LSCNO, T-c is reduced in proportion to the decrease of gamma(s). These findings can be explained phenomenologically by a simple model in which Ni impurities bring about strong pair breaking at the edges of the coherent nodal part of the Fermi surface but in the vicinity of the nodes of the SC gap. The reduction of the SC condensation energy U-0 in LSCNO, evaluated from C-el at T less than or similar to T-c, is also understood by the same model.
• Charge-parity symmetry observed through Friedel oscillations in chiral charge-density waves

  J. Ishioka, T. Fujii, K. Katono, K. Ichimura, T. Kurosawa, M. Oda, S. Tanda

  PHYSICAL REVIEW B 84 24 245125  2011年12月 [査読有り][通常論文]
   

  We discovered a chiral behavior of Friedel oscillations (FOs), which have both triangular symmetry and inverse chirality from chiral charge-density waves (CDWs) in 1T-TiSe2 by using scanning tunneling microscopy (STM). Surprisingly, the existence of FOs with the opposite chirality to the underlying CDWs suggests that the excess electron induced by impurity reduces the local helicity of CDWs without CDW breaking. This FOs can be explained with a two-branch model with different chiralities, which permits excitation from one branch to another, that is, Dirac-type dispersion. Moreover, we found two states that correspond to electron addition and electron removal. In terms of the chirality of electrons, these two states are the same. This result provides an evidence for the charge-parity (CP) symmetry conservation in CDW systems.
• Quasiparticle relaxation dynamics in underdoped Bi2Sr2CaCu2O8+delta by two-color pump-probe spectroscopy

  Y. Toda, T. Mertelj, P. Kusar, T. Kurosawa, M. Oda, M. Ido, D. Mihailovic

  PHYSICAL REVIEW B 84 17 174516  2011年11月 [査読有り][通常論文]
   

  We investigate the relaxation dynamics of photoexcited quasiparticles (QPs) in underdoped Bi2Sr2CaCu2O8+delta (T-c = 78 K). By changing the excitation energy and polarization of the probe beam, two different types of relaxation dynamics, associated with superconducting (SC) and pseudogap (PG) QPs, are quantitatively analyzed independently. From the temperature dependencies, we obtained the SC gap, Delta(SC)(0) = 24 meV, using BCS-type temperature-dependent gap and the pseudogap, Delta(PG) = 41 meV. The pump fluence (F) dependence of the SC-dominated transients shows a contribution of the PG component above the saturation condition of the SC component (F-th = 16 mu J/cm(2)), where Cooper pairs with long-range order are fully destroyed within the photoexcited volume. Assuming a temperature-independent PG decay time, we successfully isolate the native SC transient even above F-th by subtracting the PG response from the original data. In the saturation regime, the exponential decay (recovery of SC) is fast (tau(SC) similar to 2-3 ps), suggesting an efficient nonequilibrium phonon relaxation in this compound. We also find a flat-top response preceding the exponential decay at F > F-th, which appears as a delay of SC recovery in the original data. This response is visible over the whole temperature range below T-c and its duration increases with increasing F. The response is attributable to a photoinduced SC to non-SC phase transition arising from excitation by the nonthermal QPs and/or high-frequency phonons. The consistently near-constant magnitude of the PG response at the start of the SC state recovery from the non-SC phase suggests a correlation between the SC and PG QPs.
• Magnetic Field-Induced Closure of the Spin Excitation Gap near Optimal Doping in La2-xSrxCuO4

  N. B. Christensen, J. Chang, E. Razzoli, M. Bator, Ch. Niedermayer, K. Lefmann, H. M. Ronnow, D. F. Mcmorrow, A. Schneidewind, P. Link, A. Hiess, M. Boehm, R. Mottl, S. Pailhes, M. Oda, M. Ido, N. Momono, J. Mesot

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 2011年01月 [査読有り][通常論文]
   

  We have investigated how a magnetic field applied perpendicular to the CuO2 planes of the near-optimally hole-doped high-temperature superconductor La1.855Sr0.145CuO4 (T-c approximate to 36 K) influences the low-energy magnetic excitation spectrum. Our detailed single-crystal neutron scattering experiments reveal that the gap to magnetic excitations falls off linearly with increasing field and reaches zero at the magnetic field mu H-0(s)=7 +/- 1 T required to induce long-range incommensurate magnetic order. A comparison with the electron-doped cuprate Nd1.85Ce0.15CuO4 is made and the possible link between field-induced magnetic order and Fermi surface reconstruction in cuprates is discussed.
• Time-resolved polarimetry for photoexcited QP dynamics in Bi2212

  K. Watanabe, S. Tsuchiya, Y. Toda, T. Kurosawa, M. Oda, T. Mertelj, I. Madan, V. V. Kabanov, D. Mihailovic

  Int. J. Mod. Phys. B 29, 1542031(1-7) (2015) 29 1542031  2011年 [査読有り][通常論文]
  
• Ni-impurity effects on the superconducting gap of La2-xSrxCuO4: Measurements of the electronic specific heat under magnetic fields

  T. Kurosawa, N. Momono, H. Amitsuka, M. Oda, M. Ido

  PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 S42 - S43 2010年12月 [査読有り][通常論文]
   

  We investigate the residual gamma-value of the specific heat under the magnetic field H for Ni-substituted La2-xSrxCu1-yNiyO4(x = 0.15, y = 0.015; T-c = 26.5K) and La2-xSrxCuO4(x = 0.15; T-c = 37.0 K) crystals. The reduction of the SC gap estimated by applying the Volovik's relation to Delta gamma vs. H curve is too small to explain the suppression of T-c in Ni-substituted samples, where Delta gamma is the change of gamma under H. We point out the possibility that T-c of Ni-substituted sample decreases through the reduction of the area of the coherent nodal d-wave gap in momentum space, which will play an important role in causing the superconductivity. (C) 2009 Elsevier B.V. All rights reserved.
• Electron tunneling using STM/STS on iron-based oxypnictides

  Yuuki Kawashima, Koichi Ichimura, Toru Kurosawa, Migaku Oda, Satoshi Tanda, Hiroki Takahashi, Hironari Okada, Yoichi Kamihara, Hideo Hosono

  PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 S315 - S316 2010年12月 [査読有り][通常論文]
   

  We report the electron tunneling study on SmFeAsO(1-x)F(x) (x = 0, 0.045, 0.046, 0.069) by using low temperature UHV-STM/STS. The superconducting gap and pseudogap structures are observed on x = 0.045, 0.046, 0.069. We also found similar structures on non-superconducting sample of x = 0. The value of 2 Delta(sc)/kT(c) decreases as T(c) increases. (C) 2010 Elsevier B.V. All rights reserved.
• The Fermi surface and band folding in La2-xSrxCuO4, probed by angle-resolved photoemission

  E. Razzoli, Y. Sassa, G. Drachuck, M. Mansson, A. Keren, M. Shay, M. H. Berntsen, O. Tjernberg, M. Radovic, J. Chang, S. Pailhes, N. Momono, M. Oda, M. Ido, O. J. Lipscombe, S. M. Hayden, L. Patthey, J. Mesot, M. Shi

  NEW JOURNAL OF PHYSICS 12 125003  2010年12月 [査読有り][通常論文]
   

  A systematic angle-resolved photoemission study of the electronic structure of La2-xSrxCuO4 in a wide doping range is presented in this paper. In addition to the main energy band, we observed a weaker additional band, the (pi, pi) folded band, which shows unusual doping dependence. The appearance of the folded band suggests that a Fermi surface reconstruction is doping dependent and could already occur at zero magnetic field.
• Chiral Charge-Density Waves

  J. Ishioka, Y. H. Liu, K. Shimatake, T. Kurosawa, K. Ichimura, Y. Toda, M. Oda, S. Tanda

  PHYSICAL REVIEW LETTERS 105 17 2010年10月 [査読有り][通常論文]
   

  We discovered the chirality of charge-density waves (CDW) in 1T-TiSe(2) by using STM and time-domain optical polarimetry. We found that the CDW intensity becomes Ia(1):Ia(2):Ia(3) 1:0.7 +/- 0.1:0.5 +/- 0.1, where Ia(i) (i = 1, 2, 3) is the amplitude of the tunneling current contributed by the CDWs. There were two states, in which the three intensity peaks of the CDW decrease clockwise and anticlockwise. The chirality in CDW results in the threefold symmetry breaking. Macroscopically, twofold symmetry was indeed observed in optical measurement. We propose the new generalized CDW chirality H(CDW) equivalent to q(1) . (q(2) x q(3)), where q(i) are the CDW q vectors, which is independent of the symmetry of components. The nonzero H(CDW)-the triple-q vectors do not exist in an identical plane in the reciprocal space-should induce a real-space chirality in CDW system.
• Chiral Charge-Density Waves

  J. Ishioka, Y. H. Liu, K. Shimatake, T. Kurosawa, K. Ichimura, Y. Toda, M. Oda, S. Tanda

  PHYSICAL REVIEW LETTERS 105 17 176401  2010年10月 [査読有り][通常論文]
   

  We discovered the chirality of charge-density waves (CDW) in 1T-TiSe(2) by using STM and time-domain optical polarimetry. We found that the CDW intensity becomes Ia(1):Ia(2):Ia(3) 1:0.7 +/- 0.1:0.5 +/- 0.1, where Ia(i) (i = 1, 2, 3) is the amplitude of the tunneling current contributed by the CDWs. There were two states, in which the three intensity peaks of the CDW decrease clockwise and anticlockwise. The chirality in CDW results in the threefold symmetry breaking. Macroscopically, twofold symmetry was indeed observed in optical measurement. We propose the new generalized CDW chirality H(CDW) equivalent to q(1) . (q(2) x q(3)), where q(i) are the CDW q vectors, which is independent of the symmetry of components. The nonzero H(CDW)-the triple-q vectors do not exist in an identical plane in the reciprocal space-should induce a real-space chirality in CDW system.
• Nonequilibrium Carrier Dynamics Studied in Underdoped Bi2212 by Polarized Optical Pump-Probe Spectroscopy

  Y. Toda, J. Sekiya, Y. H. Liu, N. Momono, M. Oda, M. Ido

  JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 23 5 871 - 872 2010年07月 [査読有り][通常論文]
   

  We investigate nonequilibrium quasiparticle dynamics measured by ultrafast optical spectroscopy on underdoped Bi2212 crystals, which provide direct evidence that superconducting (SC) and pseudogap (PG) quasiparticies coexist below T. We verify that the ratio of signals from SC and PG quasiparticles depends on both excitation energy and polarization of the probe beam due to the anisotropy of the probe transition matrix elements and the interband transition probability. Based on this property, we successfully separate the SC or PG component and precisely evaluate the temperature dependence of them across T-c.
• Impurity Effects on Energy Gap in Bi2Sr2CaCu2O8+y Investigated by Electronic Raman Scattering

  N. Momono, T. Kurosawa, Y. Amakai, Y. Sato, T. Suzuki, H. Takano, S. Murayama, A. Sakai, M. Oda, M. Ido

  JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 23 5 785 - 787 2010年07月 [査読有り][通常論文]
   

  The Raman scattering experiments were carried out in Zn-doped and Zn-free Bi2Sr2CaCu2O8+y with optimal hole concentration below and above T-c. The energy of pair-breaking peak in the B-1g Raman spectrum, corresponding to the magnitude of superconducting gap 2 Delta 0, is suppressed by 1% Zn-doping. In the normal state, the B-1g Raman spectrum for Zn-doped sample shows no pseudogap behaviour, suggesting that the pseudogap is strongly smeared by Zn-doping.
• Measurement of chirality of charge-density-waves in TiSe2 by using STM

  J. Ishioka, Y. H. Liu, K. Shimatake, T. Kurosawa, K. Ichimura, Y. Toda, M. Oda, S. Tanda

  PHYSICA B-CONDENSED MATTER 405 11 S214 - S216 2010年06月 [査読有り][通常論文]
   

  We report the chirality of charge density waves (COW) in 1T-TiSe2 by using scanning tunneling microscopy (STM) measurements We found that the COW intensity becomes Ia(1) Ia(2) Ia(3) = 1 07 +/- 0 1 0 5 +/- 0 1 where Ia(1) (I = 1 2 3) is the amplitude of the tunneling current contributed by the CDWs We found two states in which the three intensity peaks of the CDW decrease clockwise and anticlockwise when we index each nesting vector in order of intensity in the Fourier transformation of the STM images We found that this difference arises from COW stacking along the c-axis at intervals of 2c(0)/3 This chirality is attributed to the helical stacking such as cholesteric liquid crystals (C) 2010 Elsevier B V All rights reserved
• Large pseudogap and nodal superconducting gap in Bi2Sr2-xLaxCuO6+delta and Bi2Sr2CaCu2O8+delta: Scanning tunneling microscopy and spectroscopy

  T. Kurosawa, T. Yoneyama, Y. Takano, M. Hagiwara, R. Inoue, N. Hagiwara, K. Kurusu, K. Takeyama, N. Momono, M. Oda, M. Ido

  PHYSICAL REVIEW B 81 9 094519  2010年03月 [査読有り][通常論文]
   

  In the present work, scanning tunneling microscopy/spectroscopy (STM/STS) measurements were carried out on underdoped Bi2Sr2-xLaxCuO6+delta and Bi2Sr2CaCu2O8+delta to clarify the origin of the pseudogap, in particular, the inhomogeneous large pseudogap. The nodal part of a d-wave pairing gap, which is under no influence of the inhomogeneous large pseudogap, was also examined by relating the homogeneous bottom part of the STS gap to a nodal d-wave gap in momentum space. We report that the inhomogeneous large pseudogap in the antinodal region links to a two-dimensional electronic charge order, and that the gap size of the nodal d-wave part Delta(sc) scales with the superconducting critical temperature T-c in the pseudogap regime.
• Dielectric Properties in CaCu3Ti4O12 Single Crystal at High Temperatures

  K. Kawatani, M. Takesada, M. Fukunaga, M. Oda, M. Ido, A. Onodera

  FERROELECTRICS 402 200 - 205 2010年 [査読有り][通常論文]
   

  High-temperature dielectric properties of perovskite-related CaCu3Ti4O12 single and polycrystalline samples were studied. Both samples show a very similar high dielectric response, while the value of single crystal is about two times as large as those of polycrystalline ceramic samples. The dielectric constant shows a shoulder-like round anomaly around 600 K with increasing temperature, and a dielectric anomaly at 726 K for the present single crystal (732 K for ceramic samples). The present evidence means that a structural phase transition occurs in CaCu3Ti4O12 at 726 K. The origin of high dielectric response is not related to an extrinsic one due to grains and grain boundary layers.
• Spectroscopic evidence for preformed Cooper pairs in the pseudogap phase of cuprates

  M. Shi, A. Bendounan, E. Razzoli, S. Rosenkranz, M. R. Norman, J. C. Campuzano, J. Chang, M. Mansson, Y. Sassa, T. Claesson, O. Tjernberg, L. Patthey, N. Momono, M. Oda, M. Ido, S. Guerrero, C. Mudry, J. Mesot

  EPL 88 2 2009年10月 [査読有り][通常論文]
   

  Angle-resolved photoemission on underdoped La(1.895)Sr(0.105)CuO(4) reveals that in the pseudogap phase, the dispersion has two branches located above and below the Fermi level with a minimum at the Fermi momentum. This is characteristic of the Bogoliubov dispersion in the superconducting state. We also observe that the superconducting and pseudogaps have the same d-wave form with the same amplitude. Our observations provide direct evidence for preformed Cooper pairs, implying that the pseudogap phase is a precursor to superconductivity. Copyright (C) EPLA, 2009
• Dielectric and Thermal Properties of Single-Crystalline CaCu3Ti4O12 at High Temperatures

  Akira Onodera, Keiichi Kawatani, Masaki Takesada, Migaku Oda, Masayuki Ido

  JAPANESE JOURNAL OF APPLIED PHYSICS 48 9 2009年09月 [査読有り][通常論文]
   

  The dielectric and thermal properties of perovskite-related CaCu3Ti4O12 single crystals were studied at high temperatures. A dielectric anomaly was confirmed at T-1 = 726 K, while it was previously reported to be 732 K for ceramic samples. With increasing temperature, the dielectric constant epsilon shows a shoulder-like round anomaly at around 600 K and a peak (epsilon(peak) similar to 6.0 x 10(5) at f = 1 MHz.) at T-1. CaCu3Ti4O12 exhibits an enormously high dielectric constant in both single crystals and ceramics even at high temperatures. Heat capacity was measured with an ac calorimeter, and the results also showed an anomaly around T-1. The present evidence indicates that CaCu3Ti4O12 undergoes a phase transition at T-1 in addition to the antiferromagnetic phase transition at 25 K. (C) 2009 The Japan Society of Applied Physics
• Electronic structure of La1.48Nd0.4Sr0.12CuO4 probed by high- and low-energy angle-resolved photoelectron spectroscopy

  T. Claesson, M. Mansson, A. Onsten, M. Shi, Y. Sassa, S. Pailhes, J. Chang, A. Bendounan, L. Patthey, J. Mesot, T. Muro, T. Matsushita, T. Kinoshita, T. Nakamura, N. Momono, M. Oda, M. Ido, O. Tjernberg

  PHYSICAL REVIEW B 80 9 094503  2009年09月 [査読有り][通常論文]
   

  We present angle-resolved photoelectron spectroscopy data probing the electronic structure of the Nd-substituted high-T-c cuprate La1.48Nd0.4Sr0.12CuO4. Data have been acquired at low and high photon energies, h nu=55 and 500 eV, respectively. The two extracted Fermi surfaces show significant differences. The differences can be attributed to either the change in probing depth suggesting dissimilarity of the intrinsic electronic structure between surface and bulk regions, or a considerable c-axis dispersion signaling a strong interlayer coupling. At both photon energies, considerable spectral weight is observed at all points along the Fermi surface and the intensity distribution as well as Fermi-surface shape observed at low as well as high photon energy is markedly different from what has been previously reported for La1.28Nd0.6Sr0.12CuO4 by Zhou [Science 286, 268 (1999)].
• Magnetic-Field-Induced Soft-Mode Quantum Phase Transition in the High-Temperature Superconductor La1.855Sr0.145CuO4: An Inelastic Neutron-Scattering Study

  J. Chang, N. B. Christensen, Ch. Niedermayer, K. Lefmann, H. M. Ronnow, D. F. McMorrow, A. Schneidewind, P. Link, A. Hiess, M. Boehm, R. Mottl, S. Pailhes, N. Momono, M. Oda, M. Ido, J. Mesot

  PHYSICAL REVIEW LETTERS 102 17 177006  2009年05月 [査読有り][通常論文]
   

  Inelastic neutron-scattering experiments on the high-temperature superconductor La1.855Sr0.145CuO4 reveal a magnetic excitation gap Delta that decreases continuously upon application of a magnetic field perpendicular to the CuO2 planes. The gap vanishes at the critical field required to induce long-range incommensurate antiferromagnetic order, providing compelling evidence for a field-induced soft-mode driven quantum phase transition.
• Electronic Raman Scattering in Zn-doped Bi2Sr2CaCu2O8+delta

  N. Momono, T. Kurosawa, M. Naito, M. Oda, M. Ido, Y. Aamakai, H. Takano, S. Murayama, A. Sakai

  25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 5 150 2009年 [査読有り][通常論文]
   

  The Raman scattering spectra of optimally doped Bi2Sr2Ca(Cu1-xZnx)(2)O8+delta (x=0 and x=0.01) have been measured below and above the superconducting transition temperature T-c. In B-1g Raman spectrum, a broad pair-breaking peak is observed at T<<T-c for x=0.01 as well as for Zn free Bi2212. The peak energy of the B-1g spectrum for x=0.01(similar to 350 cm(-1)) is much smaller than that of the Zn-free sample (similar to 510 cm(-1)), suggesting that the (effective) superconducting gap is largely suppressed by 1% Zn-doping.
• On the electronic inhomogeneity of underdoped Bi2Sr2CaCu2O8+delta

  Y. H. Liu, K. Takeyama, T. Kurosawa, N. Momono, M. Oda, M. Ido

  JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 69 12 3039 - 3041 2008年12月 [査読有り][通常論文]
   

  Using scanning tunneling microscopy and spectroscopy (STM/STS), we investigated the spatial dependence of electronic structure in both the superconducting (SC) and pseudogap (PG) states of one Underdoped Bi2Sr2CaCu2O8+delta (Bi2212). It is found that this sample shows rather homogeneous electronic states on a nanometer scale both below and above T-c, supporting the contention that the spatially homogeneous electronic state exists in Bi2212. Furthermore, we emphasize that the electronic inhomogeneity reported previously [S.H. Pan, et al., Nature 413 (2001) 282; C. Howald, P. Fournier, A. Kapitulnik, Phys. Rev. B 64 (2001) 100504(R); T. Cren, et al., Phys. Rev. Lett. 84 (2000) 147; A. Hashimoto, et al., Phys. Rev. B 74 (2006) 064508] is associated with the incoherent electronic states in the antinodal regions on the Fermi surface and the Superconductivity occurring on the "Fermi arc" is spatially homogeneous. (C) 2008 Elsevier Ltd. All rights reserved.
• STM/STS study on nondispersive checkerboard superstructure in superconducting Bi2212 and La-Bi2201

  M. Ido, T. Yoneyama, Y. H. Liu, Y. Takano, N. Momono, M. Oda

  JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 69 12 3006 - 3010 2008年12月 [査読有り][通常論文]
   

  We performed STM/STS measurements on superconducting Bi2212 and La-Bi2201 in order to study the nondispersive two-dimensional (21)) electronic superstructure, namely the so-called checkerboard. The nondispersive checkerboard clearly appears within the pairing gap in both systems, although the period is different between Bi2212 (similar to 4a x 4a) and La-Bi2201 (similar to 5a x 5a). We point out that the nondispersive checkerboard originates in hole-pairs and/or quasiparticles around the antinodes of the d-wave gap. and interrelates with the spatially inhomogeneous pairing gap. (c) 2008 Elsevier Ltd. All rights reserved.
• STM/STS study in the stripe-ordered state of La2-x-yNdySrxCuO4 (x=1/8, y similar to 0.4)

  N. Momono, T. Kurosawa, T. Endo, K. Kurusu, K. Takeyama, M. Oda, M. Ido

  JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 69 12 3031 - 3033 2008年12月 [査読有り][通常論文]
   

  We performed scanning tunneling microscopy/spectroscopy (STM/STS) in the stripe-ordered state of La2-x-yNdySrxCuO4 (x = 1/8, y similar to 0.4) at T similar to 9 K (>T-c) and compared the results with those of super-conducting La2-xSrxCuO4 (x similar to 1/8). The STS spectrum of La2-x-yNdySrxCuO4 (x = 1/8, y similar to 0.4) exhibits a d-wave-like gap with broad gap-edge peaks and an asymmetrically V-shaped background. The observed gap is almost the same in magnitude and shape as that of La2-xSrxCuO4 (x similar to 1/8). This result suggests that there is a close relation between the stripe order (or correlation) and the pseudogap formation because 2 triangle(0) scales with the pseudogap temperature in La2-xSrxCuO4. (C) 2008 Elsevier Ltd. All rights reserved.
• Superconducting Gap and Pseudogap Structure in LaFeAsO1-xFx Probed by STM/STS

  Koichi Ichimura, Junya Ishioka, Toru Kurosawa, Katsuhiko Inagaki, Migaku Oda, Satoshi Tanda, Hiroki Takahashi, Hironari Okada, Yoichi Kamihara, Masahiro Hirano, Hideo Hosono

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 151 - 152 2008年11月 [査読有り][通常論文]
   

  We report the electron tunneling study on LaFeAsO1-xFx (x=0.07) using low temperature UHV-STM/STS. Tunneling spectra below T-c clearly shows the gap structure. We found three anomalies as kinks in the tunneling differential conductance curve: 1) Superconducting gap structure Delta(SC)=6 meV. 2) Small pseudogap Delta(PGS)=20 meV. 3) Large pseudogap Delta(PGL)=100-150 meV. Corresponding value of 2 Delta(SC)/k(B)T(c)=5.8 suggests strong coupling superconductivity. Tunneling spectra at T=80 K show dip structure. The kink around V=150 mV still exist.
• Anisotropic quasiparticle scattering rates in slightly underdoped to optimally doped high-temperature La(2-x)Sr(x)CuO(4) superconductors

  J. Chang, M. Shi, S. Pailhes, M. Mansson, T. Claesson, O. Tjernberg, A. Bendounan, Y. Sassa, L. Patthey, N. Momono, M. Oda, M. Ido, S. Guerrero, C. Mudry, J. Mesot

  PHYSICAL REVIEW B 78 20 205103  2008年11月 [査読有り][通常論文]
   

  An angle-resolved photoemission study of the scattering rate in the superconducting phase of the high-temperature superconductor La(2-x)Sr(x)CuO(4) with x=0.145 and x=0.17, as a function of binding energy and momentum, is presented. We observe that the scattering rate scales linearly with binding energy up to the high-energy scale E(1)similar to 0.4 eV. The scattering rate is found to be strongly anisotropic, with a minimum along the (0,0)-(pi,pi) direction. A possible connection to a quantum-critical point is discussed.
• Electronic structure near the 1/8-anomaly in La-based cuprates

  J. Chang, Y. Sassa, S. Guerrero, M. Mansson, M. Shi, S. Pailhes, A. Bendounan, R. Mottl, T. Claesson, O. Tjernberg, L. Patthey, M. Ido, M. Oda, N. Momono, C. Mudry, J. Mesot

  NEW JOURNAL OF PHYSICS 10 103016  2008年10月 [査読有り][通常論文]
   

  We report an angle-resolved photoemission study of the electronic structure of the pseudogap state in La(1.48)Nd(0.4)Sr(0.12)CuO(4) (T(c) < 7 K). Two opposite dispersing Fermi arcs are the main result of this study. Several scenarios that can explain this observation are discussed.
• Fermi-arc superconductivity, pseudogap and charge order in Bi2Sr2CaCu2O8+delta

  T. Kurosawa, M. Oda, Y. H. Liu, K. Takeyama, N. Momono, M. Ido

  JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 69 9 2265 - 2267 2008年09月 [査読有り][通常論文]
   

  We report STM/STS observations on the 4a x 4a charge order in the pseudogap (PG) and superconducting (SC) states of Bi2Sr2CaCu2O8+delta, and suggest that the charge order is associated with incoherent quasiparticle or pair states around the antinodal fermi surface (FS), which are also responsible for the PC, and it can coexist with the superconductivity caused by the pairing of coherent quasiparticles on the nodal fermi arc. We also suggest that the nanometer-scale gap inhomogeneity in the SC state, reported previously [Pan, et al, Nature 413 (2001) 282; Mommo, et al., J. Phys. Soc. Jpn. 74 (2005) 2400; Hashimoto, et al., Phys. Rev. B74 (2006) 0645081 arises from that in the PC state, which occurs around the antinodal FS. (C) 2008 Elsevier Ltd. All rights reserved.
• Tuning competing orders in La(2-x)Sr(x)CuO(4) cuprate superconductors by the application of an external magnetic field

  J. Chang, Ch. Niedermayer, R. Gilardi, N. B. Christensen, H. M. Ronnow, D. F. McMorrow, M. Ay, J. Stahn, O. Sobolev, A. Hiess, S. Pailhes, C. Baines, N. Momono, M. Oda, M. Ido, J. Mesot

  PHYSICAL REVIEW B 78 10 104525  2008年09月 [査読有り][通常論文]
   

  We report the results of a combined muon-spin rotation and neutron-scattering study on La(2-x)Sr(x)CuO(4) in the vicinity of the so-called 1/8 anomaly. Application of a magnetic field drives the system toward a magnetically ordered spin-density-wave state, which is fully developed at 1/8 doping. The results are discussed in terms of competition between antiferromagnetic and superconducting order parameters.
• Direct observation of the coexistence of the pseudogap and superconducting quasiparticles in Bi2Sr2CaCu2O8+y by time-resolved optical spectroscopy

  Y. H. Liu, Y. Toda, K. Shimatake, N. Momono, M. Oda, M. Ido

  PHYSICAL REVIEW LETTERS 101 13 137003  2008年09月 [査読有り][通常論文]
   

  We report the ultrafast optical response of quasiparticles (QPs) in both the pseudogap ( PG) and superconducting (SC) states of an underdoped Bi2Sr2CaCu2O8+y (Bi2212) single crystal measured with the time-resolved pump-probe technique. At a probe energy hw(pr) = 1.55 eV, it is found that the reflectivity change Delta R/R changes its sign at exactly T-c, which allows the direct separation of the charge dynamics of PG and SC QPs. Further systematic investigations indicate that the transient signals associated with PG and SC QPs depend on the probe beam energy and polarization. By tuning them below T-c, two distinct components can be detected simultaneously, providing evidence for the coexistence of PG and SC QPs.
• Coherent d-wave superconducting gap in underdoped La(2-x)Sr(x)CuO(4) by angle-resolved photoemission spectroscopy

  M. Shi, J. Chang, S. Pailhes, M. R. Norman, J. C. Campuzano, M. Mansson, T. Claesson, O. Tjernberg, A. Bendounan, L. Patthey, N. Momono, M. Oda, M. Ido, C. Mudry, J. Mesot

  PHYSICAL REVIEW LETTERS 101 4 047002  2008年07月 [査読有り][通常論文]
   

  We present angle-resolved photoemission spectroscopy data on moderately underdoped La(1.855)Sr(0.145)CuO(4) at temperatures below and above the superconducting transition temperature. Unlike previous studies of this material, we observe sharp spectral peaks along the entire underlying Fermi surface in the superconducting state. These peaks trace out an energy gap that follows a simple d-wave form, with a maximum superconducting gap of 14 meV. Our results are consistent with a single gap picture for the cuprates. Furthermore our data on the even more underdoped sample La(1.895)Sr(0.105)CuO(4) also show sharp spectral peaks, even at the antinode, with a maximum superconducting gap of 26 meV.
• On the relations among the pseudogap, electronic charge order and Fermi-arc superconductivity in Bi2Sr2CaCu2O8+delta

  M. Oda, Y. H. Liu, T. Kurosawa, K. Takeyama, N. Momono, M. Ido

  INTERNATIONAL SYMPOSIUM ON LATTICE EFFECTS IN CUPRATE HIGH TEMPERATURE SUPERCONDUCTORS (LEHTSC2007) 108 2008年 [査読有り][通常論文]
   

  On the basis of STM/STS, break-junction tunneling and electronic Raman scattering experiments on Bi2Sr2CaCu2O8+delta reported so far, we suggest that the static, electronic charge order is associated with inhomogeneous electronic states on antinodal parts of the Fermi surface that are outside the Fermi-arc around the node and responsible for the pseudogap, and coexists with the homogeneous superconductivity caused by the pairing of coherent quasiparticles on the Fermi-arc, the so-called "Fermi-arc superconductivity", in the real space, although the two electronic orders or the corresponding energy gaps compete with each other in the k-space.
• STM/STS study on underdoped La2-xSrxCuO4

  N. Momono, T. Goto, K. Takeyama, M. Oda, M. Ido

  PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460 965 - 966 2007年09月 [査読有り][通常論文]
   

  We performed scanning tunneling microscopy/spectroscopy (STM/STS) experiments on superconducting La2-xSrxCuO4 with x = 0.12. We observed atomically resolved STM images, which show nearly square lattice with lattice constant a = similar to 4 angstrom although many atomic defects were also observed. We found that the surface atoms form dimers and result in 2 x I superstructures. STS spectrum exhibits an asymmetric V-shaped gap with gap size Delta similar to 100 meV, which is not d-wave superconducting gap but similar to so-called zero-temperature pseudogap (ZTPG). This ZTPG-like spectrum indicates the reduction of doping level around the surface. (c) 2007 Elsevier B.V. All rights reserved.
• STM studies on electronic charge order in the PG state of Bi2212

  Y. H. Liu, K. Takeyama, M. Ishikura, N. Momono, M. Oda, M. Ido

  PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460 961 - 962 2007年09月 [査読有り][通常論文]
   

  Using scanning tunneling microscopy (STM), we confirmed a nondispersive similar to 4a(0) x 4a(0) electronic charge order, whose characteristic energy is the pseudogap (PG), in the PG state of Bi2212 above T-c. (c) 2007 Elsevier B.V. All rights reserved.
• On-board sample cleaver

  Martin Mansson, Thomas Claesson, Ulf O. Karlsson, Oscar Tjernberg, Stephane Pailhes, Johan Chang, Joeel Mesot, Ming Shi, Luc Patthey, Naoki Momono, Migaku Oda, Masayuki Ido

  REVIEW OF SCIENTIFIC INSTRUMENTS 78 7 2007年07月 [査読有り][通常論文]
   

  An on-board sample cleaver has been developed in order to cleave small and hard-to-cleave samples. To acquire good cleaves from rigid samples the alignment of the cleaving blade with respect to the internal crystallographic planes is crucial. To have the opportunity to mount the sample and align it to the blade ex situ has many advantages. The design presented has allowed us to cleave very tiny and rigid samples, e.g., the high-temperature superconductor La(2-x)SrxCuO4. Further, in this design the sample and the cleaver will have the same temperature, allowing us to cleave and keep the sample at low temperature. This is a big advantage over prior cleaver systems. As a result, better surfaces and alignments can be realized, which considerably simplifies and improves the experiments. (C) 2007 American Institute of Physics.
• STM study on the period of charge order in the PG state of Bi2212

  K. Takeyama, Y. H. Liu, T. Kurosawa, N. Momono, M. Oda, M. Ido

  INTERNATIONAL JOURNAL OF MODERN PHYSICS B 21 18-19 3220 - 3223 2007年07月 [査読有り][通常論文]
   

  STM/STS is used to examine the charge order in the pseudogap state on underdoped Bi2212 crystals with different hole-doping levels (p). We report that although the data for the period of charge order are slightly scattered, it is nearly 4a x 4a (a: the lattice constant) and exhibits no obvious dependence on p in the p-range examined.
• 4ax4a electronic charge order enhanced in the inhomogeneous pseudogap state of Bi2Sr2CaCu2O8+delta

  Y. H. Liu, K. Takeyama, T. Kurosawa, N. Momono, M. Oda, M. Ido

  PHYSICAL REVIEW B 75 21 212507  2007年06月 [査読有り][通常論文]
   

  Scanning tunneling microscopy and spectroscopy are used to examine the 4ax4a electronic charge order (CO) and the spatial dependence of energy gap in the pseudogap (PG) state above T-c on Bi2Sr2CaCu2O8+delta. We report the first observation on energy gap inhomogeneity in the PG state, together with the result that the static CO develops markedly in the inhomogeneous PG state, although it is very weak in the homogeneous PG state. This static CO, which is considered to be stabilized by the pinning of the dynamically fluctuating CO, can coexist with the superconductivity below T-c.
• When low- and high-energy electronic responses meet in cuprate superconductors

  J. Chang, S. Pailhes, M. Shi, M. Mansson, T. Claesson, O. Tjernberg, J. Voigt, V. Perez, L. Patthey, N. Momono, M. Oda, M. Ido, A. Schnyder, C. Mudry, J. Mesot

  PHYSICAL REVIEW B 75 22 224508  2007年06月 [査読有り][通常論文]
   

  The existence of coherent quasiparticles near the Fermi energy in the low-temperature state of high-temperature superconductors has been well established by angle-resolved photoemission spectroscopy (ARPES). We present a study of La(1.83)Sr(0.17)CuO(4) in the superconducting state and report an abrupt change in the quasiparticle spectral function, as we follow the dispersion of the ARPES signal from the Fermi energy to 0.6 eV. The interruption in the quasiparticle dispersion separates coherent quasiparticle peaks at low energies from broad incoherent excitations at high energies. We find that the boundary between these low-energy and high-energy features exhibits a cosine-shaped momentum dependence, reminiscent of the superconducting d-wave gap. Further intriguing similarities between characteristics of the incoherent excitations and quasiparticle properties suggest a close relation between the electronic response at high and low energies in cuprate superconductors.
• Nature of the magnetic order in the charge-ordered cuprate La(1.48)Nd(0.4)Sr(0.12)CuO(4)

  N. B. Christensen, H. M. Ronnow, J. Mesot, R. A. Ewings, N. Momono, M. Oda, M. Ido, M. Enderle, D. F. McMorrow, A. T. Boothroyd

  PHYSICAL REVIEW LETTERS 98 19 197003  2007年05月 [査読有り][通常論文]
   

  Using polarized neutron scattering we establish that the magnetic order in La(1.48)Nd(0.4)Sr(0.12)CuO(4) is either (i) one dimensionally modulated and collinear, consistent with the stripe model or (ii) two dimensionally modulated with a novel noncollinear structure. The measurements rule out a number of alternative models characterized by 2D electronic order or 1D helical spin order. The low-energy spin excitations are found to be primarily transversely polarized relative to the stripe ordered state, consistent with conventional spin waves.
• Magnetic-field-induced spin excitations and renormalized spin gap of the underdoped La(1.895)Sr(0.105)CuO(4) superconductor

  J. Chang, A. P. Schnyder, R. Gilardi, H. M. Ronnow, S. Pailhes, N. B. Christensen, Ch. Niedermayer, D. F. McMorrow, A. Hiess, A. Stunault, M. Enderle, B. Lake, O. Sobolev, N. Momono, M. Oda, M. Ido, C. Mudry, J. Mesot

  PHYSICAL REVIEW LETTERS 98 7 077004  2007年02月 [査読有り][通常論文]
   

  High-resolution neutron inelastic scattering experiments in applied magnetic fields have been performed on La(1.895)Sr(0.105)CuO(4) (LSCO). In zero field, the temperature dependence of the low-energy peak intensity at the incommensurate momentum transfer Q(IC)=(0.5,0.5 +/-delta,0),(0.5 +/-delta,0.5,0) exhibits an anomaly at the superconducting T(c) which broadens and shifts to lower temperature upon the application of a magnetic field along the c axis. A field-induced enhancement of the spectral weight is observed, but only at finite energy transfers and in an intermediate temperature range. These observations establish the opening of a strongly downward renormalized spin gap in the underdoped regime of LSCO. This behavior contrasts with the observed doping dependence of most electronic energy features.
• Neutron scattering investigations of the Abrikosov state of high-temperature superconductors

  Chang J, Mesot J, Gilardi R, Kohlbrecher J, Drew A. J, Divakar U, Lister S. J, Lee S. L, Brown S. P, Charalambous D, Forgan E. M, Dewhurst C. D, Cubitt R, Momono N, Oda M

  PHYSICA B-CONDENSED MATTER 385 35 - 37 2006年11月 [査読有り][通常論文]
  
• Muons as local probes of three-body correlations in the mixed state of type-II superconductors

  G. I. Menon, A. Drew, U. K. Divakar, S. L. Lee, R. Gilardi, J. Mesot, F. Y. Ogrin, D. Charalambous, E. M. Forgan, N. Momono, M. Oda, C. Dewhurst, C. Baines

  PHYSICAL REVIEW LETTERS 97 17 177004  2006年10月 [査読有り][通常論文]
   

  The vortex glass state formed by magnetic flux lines in a type-II superconductor is shown to possess nontrivial three-body correlations. While such correlations are usually difficult to measure in glassy systems, the magnetic fields associated with the flux vortices allow us to probe these via muon-spin rotation measurements of the local field distribution. We show via numerical simulations and analytic calculations that these observations provide detailed microscopic insight into the local order of the vortex glass and more generally validate a theoretical framework for correlations in glassy systems.
• Scanning tunneling microscopy and spectroscopy study of 4ax4a electronic charge order and the inhomogeneous pairing gap in superconducting Bi2Sr2CaCu2O8+delta

  A. Hashimoto, N. Momono, M. Oda, M. Ido

  PHYSICAL REVIEW B 74 6 064508  2006年08月 [査読有り][通常論文]
   

  We performed scanning tunneling microscopy and scanning tunneling spectroscopy (STS) measurements on underdoped Bi2212 crystals with doping levels p similar to 0.11, similar to 0.13, and similar to 0.14 to examine the nature of the nondispersive 4ax4a charge order in the superconducting state at T < T-c. The charge order appears conspicuously within the pairing gap, and low doping tends to favor the charge order. We point out the possibility that the 4ax4a charge order will be dynamical in itself, and pinned down over regions with effective pinning centers. The pinned 4ax4a charge order is closely related to the spatially inhomogeneous pairing gap structure, which has often been reported in STS measurements on high-T-c cuprates.
• mu SR measurements on the vortex lattice of La1.83Sr0.17CuO4

  AJ Drew, DOG Heron, UK Divakar, SL Lee, R Gilardi, J Mesot, FY Ogrin, D Charalambous, N Momono, M Oda, C Baines

  PHYSICA B-CONDENSED MATTER 374 203 - 206 2006年03月 [査読有り][通常論文]
   

  We report mu SR measurements of the vortex lattice in the slightly overdoped compound La2-xSrxCuO4 (x = 0.17). The magnetic phase diagram provides an interesting comparison to the more exotic phases observed in the underdoped (x = 0.10) compound. The field induced hexagonal to intrinsic square transition is observed to occur at around OAT in agreement with previous neutron measurements. (c) 2005 Elsevier B.V. All rights reserved.
• STM/STS study on local electronic states of La2-xSrxCuO4

  N. Momono, T. Goto, A. Hashimoto, K. Takeyama, Y. Ichikawa, M. Oda, M. Ido

  LOW TEMPERATURE PHYSICS, PTS A AND B 850 411 - + 2006年 [査読有り][通常論文]
   

  We performed scanning tunneling microscopy/spectroscopy (STM/STS) on overdoped La1.81Sr0.19CuO4 (T-c=33K). We can clearly see oxygen atoms on the cleaved surface of Cu-O plane. The tunneling spectrum measured on the cleaved surface is similar to the so-called zero temperature pseudogap (ZTPG), which was recently reported in lightly doped cuprates by McElroy et al.[Phys. Rev. Lett. 94, 197005 (2005)] and by Hanaguri et al. [Nature 430, 1001 (2004)]. The ZTPG-like spectrum indicates that the electronic states of the topmost Cu-O plane, where STS spectrum was measured, will be seriously modified on account of the marked reduction of the doping level.
• STM/STS study on 4ax4a electronic charge modulation of Bi2Sr2CaCu2O8+delta

  A. Hashimoto, Y. Kobatake, S. Nakamura, N. Momono, M. Oda, M. Ido

  LOW TEMPERATURE PHYSICS, PTS A AND B 850 521 - + 2006年 [査読有り][通常論文]
   

  We performed low-bias STM measurements on lightly doped Bi2212 crystals, and confirmed the development of two-dimensional (2D) superstructure with a periodicity of four lattice constants (4a) within the Cu-O layer at T < T-c. This 4a x 4a superstructure orients along the Cu-0 bonding direction, and is nondispersive. The nondispersive 4a x 4a superstructure was clearly observed within the ZTPG or d-wave gap, while it tended to fade out outside the gaps.
• STM/STS study on 4 alpha x 4 alpha electronic charge order of superconducting Bi2Sr2CaCu2O8+delta

  N Momono, A Hashimoto, Y Kobatake, M Oda, M Ido

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 9 2400 - 2403 2005年09月 [査読有り][通常論文]
   

  We performed low-bias STM measurements on underdoped Bi2212 crystals, and confirmed that a two-dimensional (2D) superstructure with a periodicity of four lattice constants (4a) is formed within the Cu-O plane at T < T-c. This 4a x 4a superstructure, oriented along the Cu-O bonding direction, is nondispersive and more intense in lightly doped samples with a zero temperature pseudogap (ZTPG) than in samples with a d-wave gap. The nondispersive 4a x 4a superstructure was clearly observed within the ZTPG or d-wave gap, while it tended to fade out outside the gaps. The present results provide a useful test for various models proposed for an electronic order hidden in the underdoped region of high-T-c cuprates.
• Combined neutron scattering and muon-spin rotation investigations of the abrikosov state of high-temperature superconductors

  J. Mesot, J. Chang, J. Kohlbrecher, R. Gilardi, A. J. Drew, U. Divakar, D. O.G. Heron, S. J. Lister, S. L. Lee, S. P. Brown, D. Charalambous, E. M. Forgan, F. Y. Ogrin, G. I. Menon, C. D. Dewhurst, R. Cubitt, C. Baines, N. Momono, M. Oda, T. Uefuji, K. Yamada

  Proceedings of SPIE - The International Society for Optical Engineering 5932 1 - 8 2005年 [査読有り][通常論文]
   

  The magnetic phase diagram of high-temperature superconductors can contain many exotic vortex phases not observed in conventional superconducting materials. For example, the familiar vortex lattice may melt at high temperatures into a vortex liquid. The influence of defects, which pin the vortices, is of particular interest from both a theoretical and an experimental point of view. We have used a combination of small angle neutron scattering (SANS) and muon-spin rotation to probe the order of the vortex system on a microscopic scale and have succeeded, for the first time, to measure a well-ordered vortex lattice (VL) structure at all doping regimes of LSCO. In the optimally to overdoped regime a field-induced transition from hexagonal to square coordination is reported. The possible connections of our neutron results to photoemission data, as well as the implications for various competing theoretical models will be discussed. In the underdoped regime we observe, as a function of applied magnetic field, a transition from an ordered vortex state to a vortex glass phase that results from the presence of random pinning. Finally, recent measurements of the VL on electron doped high-temperature superconductors are presented.
• Electronic specific heat of La2-xSrxCuO4: Pseudogap formation and reduction of the superconducting condensation energy

  T Matsuzaki, N Momono, M Oda, M Ido

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 8 2232 - 2238 2004年08月 [査読有り][通常論文]
   

  To examine the so-called small pseudogap and the superconducting (SC) condensation energy U(0), the electronic specific heat C-el was measured on La-2-Sr-x(x),CuO4 up to similar to120K. In samples with doping level p (= x) less than similar to0.2, small pseudogap behavior appears in the gamma (= C-el/T) vs T curve around the mean-field critical temperature for a d-wave superconductor T-co (= 2Delta(0)/(4-5)k(B)), where Delta(0) is the maximum gap at T much less than T-c. The condensation energy U(0) is largely reduced in the pseudogap regime (p less than or similar to 0.2). The reduction of U(0) can be well reproduced by introducing an effective SC energy scale Delta(0)(eff) = betapDelta(0) (beta = 4.5) instead of Delta(0). The effective SC energy scale is discussed in relation to the coherent pairing gap formed over the nodal Fermi arc.
• Electronic phase diagram of La2-xSrxCuO4

  M Oda, N Momono, M Ido

  JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 65 8-9 1381 - 1390 2004年08月 [査読有り][通常論文]
   

  In this article, we discuss the electronic phase diagram of a high-T-c cuprate La2-xSrxCuO4; namely, how the electronic property changes as functions of temperature T and hole-doping level p. In particular, we focus on four crossover lines, which can be seen in the T dependences of uniform magnetic susceptibility and electronic specific heat. One of them is crossover line T-a(p) in the low doping region below p similar to 0.05 near the margin of the superconducting regime, which is associated with strongly developed antiferromagnetic (AF) spin correlations within the Cu-O planes. The others are crossover lines T-max(p), T*(p) and T-sf(p) in the normal state in the superconducting regime (0.05 < p < 0.27); T-max > T* > T-sf > T-c. It is suggested that crossover lines T-max(p) and T*(p) and T-sf(p) will be associated with the gradual developments of AF spin correlations, a kind of precursor of superconductivity and superconducting critical fluctuations, respectively. (C) 2004 Elsevier Ltd. All rights reserved.
• Unusual interplay between copper-spin and vortex dynamics in slightly overdoped La1.83Sr0.17CuO4

  R Gilardi, A Hiess, N Momono, M Oda, M Ido, J Mesot

  EUROPHYSICS LETTERS 66 6 840 - 846 2004年06月 [査読有り][通常論文]
   

  Our inelastic neutron scattering experiments of the spin excitations in the slightly overdoped La1.83Sr0.17CuO4 compound show that, under the application of a magnetic field of 5 tesla, the low-temperature susceptibility undergoes a weight redistribution centered at the spin gap energy. Furthermore, by comparing the temperature dependence of the neutron data with ac susceptibility and magnetization measurements, we conclude that the filling-in of the spin gap tracks the irreversibility/inelting temperature rather than T-c2, which indicates an unusual interplay between the magnetic vortices and the spin excitations even in the slightly overdoped regime of high-temperature superconductors.
• Direct observation of the flux-line vortex glass phase in a type II superconductor

  U Divakar, AJ Drew, SL Lee, R Gilardi, J Mesot, FY Ogrin, D Charalambous, EM Forgan, GI Menon, N Momono, M Oda, CD Dewhurst, C Baines

  PHYSICAL REVIEW LETTERS 92 23 237004  2004年06月 [査読有り][通常論文]
   

  The order of the vortex state in La1.9Sr0.1CuO4 is probed using muon-spin rotation and small-angle neutron scattering. A transition from a Bragg glass to a vortex glass is observed, where the latter is composed of disordered vortex lines. In the vicinity of the transition the microscopic behavior reflects a delicate interplay of thermally induced and pinning-induced disorder.
• Superconducting condensation energy in the pseudogap region of La2-xSrxCuO4

  T Matsuzaki, M Ido, N Momono, M Oda

  PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 388 217 - 218 2003年05月 [査読有り][通常論文]
   

  The superconducting condensation energy at T = 0, U-0, was examined from the measurements of the electronic specific heat C-el on La2-xSrxCuO4. We reconfirmed that U-0 is markedly reduced in the pseudogap regime (x less than or similar to 0.2). The doping-level (p) dependence of U-0 as well as T, can be explained in the pseudogap regime by introducing an effective energy gap Delta(eff) = betapDelta(0) (beta = 4.5) instead of the maximum gap Delta(0) at T much less than T-c. (C) 2003 Elsevier Science B.V. All rights reserved.
• Doping dependence of the tetragonal-orthorhombic phase transition in the superconducting compound La2-xSrxCuO4 +/-delta

  R Gilardi, Stahn, I, F Altorfer, N Momono, M Oda, J Mesot

  APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING 74 S1624 - S1626 2002年12月 [査読有り][通常論文]
   

  The phase transition from tetragonal to orthorhombic structure in the high-temperature superconductor La2-xSrxCuO4+/-delta (La214) has been studied by means of elastic neutron scattering. Both underdoped (x = 0.09) and over-doped (x = 0.17) compounds have been investigated. From the temperature dependence of the superstructure peaks, we are able to estimate the critical exponent beta, which is found to increase with increasing x. We also observe that the temperature interval over which the critical behaviour appears to be valid is unusually large and strongly doping-dependent.
• Superconducting condensation energy and pseudogap formation in La2-xSrxCuO4: New energy scale for superconductivity

  N Momono, T Matsuzaki, M Oda, M Ido

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 71 12 2832 - 2835 2002年12月 [査読有り][通常論文]
   

  The electronic specific heat C-el was measured for La2-xSrxCuO4 to examine the superconducting condensation energy at T = 0, U-0. We reconfirmed that U-0 is markedly reduced even in slightly underdoped samples whose T-c's are still more than 30 K. The reduction of U-0 results from the suppression of the effective superconducting gap, in addition to that of the density of states at the Fermi level E-F, caused by the pseudogap formation in the normal state. The doping-level (p) dependence of U-0 as well as T-c can be explained over a wide p range by introducing an effective energy gap Delta(eff) = betapDelta(0) (beta = 4.5) instead of Delta(0), where Delta(0) is the maximum gap at T << T-c.
• Energy gap evolution in the tunneling spectra of Bi2Sr2CaCu2O8+delta

  RM Dipasupil, M Oda, N Momono, M Ido

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 71 6 1535 - 1540 2002年06月 [査読有り][通常論文]
   

  On the basis of the tunneling spectra in Bi2212/vaccum/Bi2212 junctions fabricated using STM, we report that, in the electronic excitations, there exist two kinds of pseudogaps; one with a characteristic energy comparable to the superconducting (SC) gap and another one that is 3 to 4 times larger. The smaller energy-scale pseudogap (SPG) develops progressively below temperature T*, which nearly scales with the SC gap amplitude Delta(0) at T much less than T-c, in addition to the larger energy-scale pseudogap (LPG), which already exists above T*. The SPG smoothly develops into the SC-state gap with no tendency to close at T-c.
• Direct evidence for an intrinsic square vortex lattice in the overdoped high-T-c superconductor La1.83Sr0.17CuO4+delta

  R Gilardi, J Mesot, A Drew, U Divakar, SL Lee, EM Forgan, O Zaharko, K Conder, VK Aswal, CD Dewhurst, R Cubitt, N Momono, M Oda

  PHYSICAL REVIEW LETTERS 88 21 217003  2002年05月 [査読有り][通常論文]
   

  We report here the first direct observations of a well ordered vortex lattice in the bulk of a La2-xSr xCuO4+delta single crystal (slightly overdoped, x=0.17 ). Our small angle neutron scattering investigation of the mixed phase reveals a crossover from triangular to square coordination with increasing magnetic field. The existence of an intrinsic square vortex lattice has never been observed in high-temperature superconductors and is indicative of the coupling of the vortex lattice to a source of anisotropy, such as those provided by a d -wave order parameter or the presence of stripes.
• Direct Evidence for an Intrinsic Square Vortex Lattice in the Overdoped High- [Formula presented] Superconductor [Formula presented]

  R. Gilardi, J. Mesot, A. Drew, U. Divakar, S. L. Lee, E. M. Forgan, O. Zaharko, K. Conder, V. K. Aswal, C. D. Dewhurst, R. Cubitt, N. Momono, M. Oda

  Physical Review Letters 88 21 4  2002年 [査読有り][通常論文]
   

  We report here the first direct observations of a well ordered vortex lattice in the bulk of a [Formula presented] single crystal (slightly overdoped, [Formula presented]). Our small angle neutron scattering investigation of the mixed phase reveals a crossover from triangular to square coordination with increasing magnetic field. The existence of an intrinsic square vortex lattice has never been observed in high-temperature superconductors and is indicative of the coupling of the vortex lattice to a source of anisotropy, such as those provided by a [Formula presented]-wave order parameter or the presence of stripes. © 2002 The American Physical Society.
• Tunneling studies on the energy gap evolution in Bi2Sr2CaCu2O8+delta

  M Oda, N Momono, M Ido

  SUPERCONDUCTING AND RELATED OXIDES: PHYSICS AND NANOENGINEERING V 4811 195 - 205 2002年 [査読有り][通常論文]
   

  We report, on the basis of our recent tunneling experiments over wide temperature (7) and hole-doping (p) ranges in Bi2212/vaccum/Bi2212 junctions fabricated using STM, that in the electronic excitation spectrum, there exist two kinds of pseudogaps (LPG and SPG) with different characteristic energies. The LPG, which is 3 to 4 times larger than the superconducting (SC) gap magnitude 2Delta(0), develops below similar toT(max), where the magnetic susceptibility starts to decrease because of the gradual development of antiferromagnetic spin fluctuations. On the other hand, the SPG, whose magnitude is comparable to 2Delta(0), develops progressively, in addition to the LPG, below the mean-field characteristic temperature T-co for d-wave superconductors, and then evolves into the SC-gap below T-c suggesting that it will be some kind of precursor of superconductivity. Furthermore, in accordance with the SC transition, the high-energy feature of quasiparticle spectrum outside the SC-gap, changes from a broad hump to a clear dip and hump accompanied by a shift of the hump position toward lower energies, in addition to the rapid growth of SC-gap from SPG. We also report that T-c nearly scales with the product of Delta(0) and p, k(B)T(c)similar topDelta(0); the effective SC gap is -pDelta(0) in high-T-c cuprates, instead of Delta(0) in conventional BCS superconductors.
• Observation of the Andreev reflection in the c-axis transport of Bi2Sr2CaCu2O8+x single crystals near T-c and the search for the preformed-pair state

  HS Chang, HJ Lee, M Oda

  PHYSICAL REVIEW B 64 13 134504  2001年10月 [査読有り][通常論文]
   

  We observed an enhancement of the c-axis differential conductance around the zero bias. in Au/Bi2Sr2CaCu2O8+x (Bi2212) junctions near the superconducting transition temperature T-c. We attribute the conductance enhancement to the Andreev reflection between the surface Cu-O bilayer with suppressed superconductivity and the neighboring superconducting inner bilayer. The continuous evolution from depression to an enhancement of the zero-bias differential conductance, as the temperature approaches T-c from below, points to weakening of the barrier strength of the nonsuperconducting layer between adjacent Cu-O bilayers. We observed that the conductance enhancement persisted up to a few degrees above T-c in junctions prepared on slightly overdoped Bi2212 crystals. However, no conductance enhancement was observed above T-c in under-doped crystals, although a recently proposed theoretical consideration suggests an even wider temperature range of enhanced zero-bias conductance. This seems to provide a negative perspective to the existence of the phase-incoherent preformed pairs in the pseudogap state.
• Observation of the Andreev reflection in the (formula presented)-axis transport of (formula presented) single crystals near (formula presented) and the search for the preformed-pair state

  Hyun-Sik Chang, Hu-Jong Lee, Migaku Oda

  Physical Review B - Condensed Matter and Materials Physics 64 13 2001年 [査読有り][通常論文]
   

  We observed an enhancement of the c-axis differential conductance around the zero bias in (formula presented) (Bi2212) junctions near the superconducting transition temperature (formula presented) We attribute the conductance enhancement to the Andreev reflection between the surface Cu-O bilayer with suppressed superconductivity and the neighboring superconducting inner bilayer. The continuous evolution from depression to an enhancement of the zero-bias differential conductance, as the temperature approaches (formula presented) from below, points to weakening of the barrier strength of the nonsuperconducting layer between adjacent Cu-O bilayers. We observed that the conductance enhancement persisted up to a few degrees above (formula presented) in junctions prepared on slightly overdoped Bi2212 crystals. However, no conductance enhancement was observed above (formula presented) in underdoped crystals, although a recently proposed theoretical consideration suggests an even wider temperature range of enhanced zero-bias conductance. This seems to provide a negative perspective to the existence of the phase-incoherent preformed pairs in the pseudogap state. © 2001 The American Physical Society.
• Hyperbolic Dependence of 2Δ₀ VS. Tc Ratio on Hole-Doping Level in High-Tc Cuprates : Energy scale in Determining Tc

  Oda, M, Dipasupil, RM, Momono, N, Ido, M

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 69 3 983 - 984 2000年03月 [査読有り][通常論文]
  
• Energy scale in determining the T(c) of cuprate superconductors

  M Oda, N Momono, M Ido

  SUPERCONDUCTING AND RELATED OXIDES: PHYSICS AND NANOENGINEERING IV 4058 18 - 29 2000年 [査読有り][通常論文]
   

  In La(2-x)Sr(x)CuO(4) (La214) and Bi(2)Sr(2)CaCu(2)O(8+delta) (Bi2212), scanning tunneling spectroscopy (STS), break-junction tunneling spectroscopy (BJTS) and Raman scattering spectroscopy demonstrate that the superconducting-state energy gap Delta (o) at T much less thanT(c) increases monotonically with the lowering of hole-doping level p even below the optimal doping p(o), where T(c) begins to decrease. On the basis of electronic specific heat, magnetic susceptibility, resistivity and STS data in La214, it is suggested that a pseudogap of almost the same energy scale as Delta (o), a small energy scale pseudogap (SPG), will develop progressively below a certain temperature T* in La214 as in Bi2212. In the two systems, the size of SPG (Delta (S)(pG)), comparable to Delta (o), essentially scales with SPG temperature T*; Delta (S)(PG)similar to Delta (o)similar to (2.3+/-0.3)k(B)T*. We also report the relation among Delta (o), higher crossover temperature T(max) (>T*) and the corresponding large energy scale pseudogap (LPG) Delta (L)(PG); Delta (L)(PG)similar to 3k(B)T(max)similar to alpha Delta (o) (alpha =3 similar to4 for Bi2212 and alpha =6 similar to8 for La214). Furthermore, we report that T(c) almost scales with p Delta (o) over a wide p range, except for high doping levels (p/p(o)greater than or similar to1.3), where T(c) is very close to the BCS expectation (T(c)=2 Delta (o)/4.3k(B)). We discuss some scenarios for the superconducting transition, where the energy scale in determining T(c) is expected to be of order p Delta (o).
• Superconducting gap in tunneling spectra and pseudogap behavior on high-T-c cuprates

  M Oda, RM Dipasupil, N Momono, S Saigo, T Nakano, M Ido

  INTERNATIONAL JOURNAL OF MODERN PHYSICS B 13 29-31 3605 - 3609 1999年12月 [査読有り][通常論文]
   

  Superconducting gap magnitude 2 Delta(o) is re-examined by STM/STS at T much less than T-c in Bi2212. It is confirmed that 2 Delta(o) increases monotonically with lowering the doping level p and almost scales with pseudogap temperature T* over the entire p range examined; 2 Delta(o)(p)similar to 4.3k(B)T* (p). Furthermore, it is shown that T-c is almost given by renormalizing 2 Delta(o) or T* with p; k(B)T(c)(p)proportional to p Delta(o)(p) or T-c(p)proportional to pT*(p).
• Superconducting gap in the tunneling spectra of high-T-c cuprates

  M Oda, K Hoya, N Abe, M Yokoyama, N Momono, T Nakano, T Nagata, M Ido

  INTERNATIONAL JOURNAL OF MODERN PHYSICS B 12 29-31 3179 - 3182 1998年12月 [査読有り][通常論文]
   

  In Bi2212 and La214, the low-T (T << T-c) superconducting gap magnitude 2 Delta(0) and the temperature dependence of in-plane resistivity rho were examined over a wide carrier-doping range. In both systems, 2 Delta(0) increases with lowering doping level and rho starts decreasing faster around a temperature T*, comparable to the mean-field T-c or the onset temperature of a spin-channel singlet formation in the mean-field RVB theory, each of which is given by similar to Delta(0)/2k(B).
• Strong pairing interaction and pseudogap behavior in underdoped Bi2Sr2CaCu2O8+delta

  M Oda, K Hoya, N Momono, T Nakano, A Sakai, M Ido

  JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 59 10-12 2071 - 2073 1998年10月 [査読有り][通常論文]
   

  We report STM/STS and Raman experiments on the Bi2212 superconducting gap in a doping range from p similar to 0.1 to similar to 0.21. The gap magnitude 2 Delta(o) at T much less than T-c increases with lowering p even in the underdoped region, as in the p dependence of the onset temperature T* of a pseudogap. T* is in qualitative agreement with the mean-field value of T-c, T-c(MF), Obtained from 2 Delta(o). This result indicates that T* corresponds to T-c(MF), suggesting convincingly that incoherent pairs are preformed below T*. (C) 1998 Elsevier Science Ltd. All rights reserved.
• Contrasting Ni- and Zn-substitution effects on magnetic properties and superconductivity in La2-xSrxCuO4

  T Nakano, N Momono, T Nagata, M Oda, M Ido

  PHYSICAL REVIEW B 58 9 5831 - 5838 1998年09月 [査読有り][通常論文]
   

  Both Ni- and Zn-substitution; effects on Superconducting and magnetic properties of La2-xSrxCuO4 were studied by measuring the magnetic susceptibility chi and the electronic specific heat C-el at T much less than T-c. In Ni-substituted samples with x greater than or equal to 0.14, the local nature of the spin correlation among 3d spins remains almost unchanged even on Ni sites at low Ni concentrations, where Ni atoms are substituted as Ni3+ ions. On the other hand, in Zn-substituted samples the 3d-spin correlation is seriously disturbed on host Cu sites around each Zn site. The depression of T-c and the residual gamma value at T much less than T-c indicate that the suppression of the superconductivity in Zn,substituted samples is much stronger than that in Ni3+-substituted ones. The suppression of the superconductivity in the Ni3+-substituted samples can be understood in the context of a potential scattering of the Cooper pairs in a d-wave superconductor. On the other hand, the strong suppression of the superconductivity in the Zn-substituted samples will occur through the local disturbance of the 3d-spin correlation on host Cu sites around each Zn ion.
• Contrasting Ni- and Zn-substitution effects on magnetic properties and superconductivity in La2-xSrxCuO4

  Nakano T, Momono N, Nagata T, Oda M, Ido M

  PHYSICAL REVIEW B 58 9 5831 - 5838 1998年09月 [査読有り][通常論文]
  
• Contrasting Ni- and Zn-substitution effects on magnetic properties and superconductivity in La2-xSrxCuO4

  Nakano, T, Momono, N, Nagata, T, Oda, M, Ido, M

  PHYSICAL REVIEW B 58 9 5831 - 5838 1998年09月 [査読有り][通常論文]
  
• Correlation between the doping dependences of superconducting gap magnitude 2 Delta(o) and pseudogap temperature T* in high-T-c cuprates

  T Nakano, N Momono, M Oda, M Ido

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 67 8 2622 - 2625 1998年08月 [査読有り][通常論文]
   

  We report that in La2-xSrxCuO4 (La214) and Bi2Sr2CaCu2O8+delta (Bi2212) the resistivity rho and magnetic susceptibility chi decrease more sharply below T*, corresponding to the onset temperature of a spin gap (pseudogap) at least for Bi2212. In each system, Ti scales with the superconducting gap magnitude 2 Delta(0) (T* similar to 2 Delta(0)/4.3k(B)), which increases as the doping level is lowered. We also report that 2 Delta(0) is almost proportional to T-max (>T*), where T-max is the temperature exhibiting a broad peak of chi and k(B)T(max) has been considered to give the measure of effective exchange energy J(eff); the alpha factors in 2 Delta(0) similar to alpha k(B)T(max) similar to alpha J(eff) are nearly one and two for La214 and Bi2212, respectively.
• Strong pairing interactions in the underdoped region of Bi2Sr2CaCu2O8+delta

  M Oda, K Hoya, R Kubota, C Manabe, N Momono, T Nakano, M Ido

  PHYSICA C 281 2-3 135 - 142 1997年08月 [査読有り][通常論文]
   

  Doping effects on the superconducting gap of Bi2Sr2CaCu2O8+delta have been studied for 0.1 less than or similar to p less than or similar to 0.21 by STM/STS. The gap is consistent with d(x2-y2) symmetry in the p-range examined. The gap magnitude 2 Delta(o) increases with decreasing p even below p(0) similar to 0.17, at which T-c starts to decrease, and seems to correlate with the development of an antiferromagnetic correlation. The in-plane resistivity is reduced just like a superconducting precursor below T*, at which pseudogaps open in the electronic and magnetic energy spectra. Furthermore, the reduced gap 2 Delta(o)/k(B)T* is nearly constant for p less than or similar to 0.21, 4 similar to 5, comparable to the mean field value 2 Delta(0)/k(B)T(c0) similar to 4.3 for d-wave pairing states. These results suggest convincingly that incoherent pairs are preformed well above T-c at low doping levels where the pairing interaction is extremely strong but T-c is largely reduced. (C) 1997 Elsevier Science B.V.
• STM/STS studies for doping effects on the symmetry and magnitude of superconducting gap in Bi2Sr2CaCu2O8+delta

  M Oda, K Hoya, R Kubota, C Manabe, N Momono, T Nakano, M Ido

  PHYSICA C 282 1499 - 1500 1997年08月 [査読有り][通常論文]
   

  Doping effects on the superconducting gap of BSCCO have been studied over a wide doping range from p-0.1 to 0.21, including the under-and overdoped crystals, by using STM/STS. The gap is consistent with d(x)2-(y)2 symmetry over the doping range examined. The gap magnitude 2 Delta(o), corresponding to the strength of pairing interaction, increases with decreasing p even in the underdoped region where T-c is largely reduced.
• Atomic images and tunneling spectra on Bi2Sr2CaCu2O8+delta cleaved surface by STM

  C Manabe, M Oda, M Ido

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 66 6 1776 - 1784 1997年06月 [査読有り][通常論文]
   

  Atomic images of the Bi-O and Cu-O planes were selectively observed in STM experiments on slightly underdoped Bi2Sr2CaCu2O8+delta by changing bias voltage, and tunneling spectra were measured while observing the Cu-O plane at three tip heights (h(1) > h(2) > h(3)). The Cu-O plane images indicate that the conduction holes go mainly into O 2p(sigma), and Cu 3d(x2-y2) 2 orbitals. The spectra for h(1) and h(2) are consistent with a gap having lines of nodes at the directions 45 degrees from the Cu-O bonds, as shown in our previous work. On the other hand, the spectra for h(3), where the tip seems to be very close to the specimen surface, are quite similar to expectations for the pair-breaking due to non-magnetic impurities in a d-wave superconductor. This, combined with the result for the node directions, strongly supports a d(x2-y2) superconducting gap.
• THE CRYSTALLOGRAPHIC SYMMETRIES OF SINGLE BAPB1-XBIXO3 CRYSTALS GROWN FROM BACO3-PBO2-BI2O3 SOLUTIONS

  ODA, M, HIDAKA, Y, KATSUI, A, MURAKAMI, T

  SOLID STATE COMMUNICATIONS 60 12 897 - 900 1996年12月 [査読有り][通常論文]
  
• STM and STS studies on the superconducting gap symmetry of Bi2Sr2CaCu2O8+delta

  M Oda, C Manabe, T Abe, M Ido

  PHYSICA C 263 1-4 241 - 244 1996年05月 [査読有り][通常論文]
   

  We have measured tunneling spectra of Bi2Sr2CaCu2O8+delta while observing the Cu-O plane STM image at T = 6 K. The low-temperature spectra are consistent with a superconducting gap with line nodes along the directions of 45 degrees from the Cu-O bond directions, possibly a d(x2-y2) gap.
• STM images of a superconducting Cu-O plane and the corresponding tunneling spectrum in Bi2Sr2CaCu2O8+delta

  M Oda, C Manabe, M Ido

  PHYSICAL REVIEW B 53 5 2253 - 2256 1996年02月 [査読有り][通常論文]
   

  Clear atomic images of Bi2Sr2CaCu2O8+delta cleaved surfaces have been observed at T=6 and 300 K by scanning tunneling microscopy (STM). The atomic images taken for bias voltages much lower than the Bi-O plane semiconducting gap E(g) similar to 100 meV, corresponding to the Cu-O plane, indicate that the conduction electrons exist mainly in the Cu 3d(x2-y2) and O 2p(sigma) orbitals. Tunneling spectra have been also measured in the same processes as in the Cu-O plane STM image observations at T=6 K. The low-temperature spectra are in good agreement with that in a d-wave superconductor with an anisotropic Fermi surface on which the normal density of states N(k(F)) is largest (N-max) for the maximum gap directions and decreases to similar to N-max/2 for the node directions. This, combined with the result on the N(k(F)) anisotropy in photoemission experiments, is consistent with a d(x2-y2) superconducting gap.
• Spin susceptibility of La2-xSrxCuO4; modification of localized character of Cu 3d-electrons at x≳0.15

  T. Nakano, K. Yamaya, N. Momono, M. Oda, M. Ido

  Journal of Low Temperature Physics 105 3-4 395 - 400 1996年 [査読有り][通常論文]
   

  The magnetic susceptibility χ of superconducting La2-xSrxCuO4 (LSCO) was investigated over a wide x-range. The effective magnetic moment on the Cu-site of LSCO is progressively suppressed at x≳0.15 owing to deterioration of the localized character of Cu 3d-electrons, and the superconducting transition temperature Tc begins to decrease near x=0.15. The density of states at the Fermi level, estimated from the electronic specific heat or the T-independent spin part of χ, is enhanced above x ∼0.15. © 1996 Plenum Publishing Corporation.
• STM images of a superconducting Cu-O plane and the corresponding tunneling spectrum

  M. Oda, C. Manabe, M. Ido

  Physical Review B - Condensed Matter and Materials Physics 53 5 2253 - 2256 1996年 [査読有り][通常論文]
   

  Clear atomic images of (Formula presented)(Formula presented)(Formula presented)(Formula presented) cleaved surfaces have been observed at T=6 and 300 K by scanning tunneling microscopy (STM). The atomic images taken for bias voltages much lower than the Bi-O plane semiconducting gap (Formula presented)∼100 meV, corresponding to the Cu-O plane, indicate that the conduction electrons exist mainly in the Cu 3(Formula presented) and O 2(Formula presented) orbitals. Tunneling spectra have been also measured in the same processes as in the Cu-O plane STM image observations at T=6 K. The low-temperature spectra are in good agreement with that in a d-wave superconductor with an anisotropic Fermi surface on which the normal density of states N((Formula presented)) is largest ((Formula presented)) for the maximum gap directions and decreases to ∼(Formula presented)/2 for the node directions. This, combined with the result on the N((Formula presented)) anisotropy in photoemission experiments, is consistent with a (Formula presented) superconducting gap. © 1996 The American Physical Society.
• Pressure effects on superconductivity and structural phase transition in La1.8-xNd0.2BaxCuO4

  M Ido, R Sakamoto, J Tsuda, O Akahane, N Momono, T Nakano, C Manabe, M Oda

  CZECHOSLOVAK JOURNAL OF PHYSICS 46 1235 - 1236 1996年 [査読有り][通常論文]
   

  The structural transition at T-1(similar to 110 K) of La1.8-xNd0.2BaxCuO4 (x=0.1) disappears above 1GPa, but the superconducting critical temperature T-c increases monotonically with pressure over the whole pressure range examined (0 less than or equal to P less than or equal to 2GPa). On the other hand, the structural transition for x=0.125 persists up to, at least, 2GPa, though it jumps to the temperature T*(similar to 60 K), where the charge (hole) ordering occurs, at pressures above 1.5GPa The structural change for x=0.125 is appreciably depressed at P greater than or equal to 1.5GPa and T-c is largely restored.
• Atomic images of the Bi-O plane on Bi2Sr2CaCu2O8+delta cleaved surface by STM

  M Oda, C Manabe, T Abe, R Kubota, Y Kamada, T Nakano, N Momono, M Ido

  CZECHOSLOVAK JOURNAL OF PHYSICS 46 1429 - 1430 1996年 [査読有り][通常論文]
   

  Atomic images of the semiconducting Bi-O plane on Bi2Sr2CaCu2O8+delta cleaved surface have been observed by STM. For the as-grown crystals, the images show strong modulations in the in-plane atomic interval and in the brightness. The in-plane atomic interval in the relatively bright regions (RBR) is 20 similar to 30 % smaller than that in the relatively dark regions (RDR). It is shown that the density of tunneling electrons in RBR is larger than that in RDR, that is, a kind of charge-density-wave (CDW) is formed in the Bi-O plane. Magnitudes of the structural modulation and the semiconducting gap are both reduced by annealing. Such a correlation suggests that the origin of the semiconducting Bi-O plane might be attributed to the structural modulation.
• Investigation of impurity effects in La(2-x)Sr(x)Cu(1-y)M(y)O(4) (M=Ga,Zn) by electronic specific heat

  N Momono, T Nakano, A Eida, K Chida, Y Miura, M Oda, M Ido

  CZECHOSLOVAK JOURNAL OF PHYSICS 46 1233 - 1234 1996年 [査読有り][通常論文]
   

  The electronic specific heat C-cl was studied at T less than or equal to 10K on Ga- and Zn-doped La2-xSrxCuO4 (0.16 less than or equal to x less than or equal to 0.22). In pure La2-xSrxCuO4 (0.16 less than or equal to x less than or equal to 0.22), the C-cl at T much less than T-c contains only a T-2 component but no T-linear one, which is peculiar to a clean d-wave superconductor. Partial substitution of Ga or Zn for Cu changes the T-2-term of C-cl into a quite different one described by the sum of a T-linear and a nearly T-3 term. The coefficient of the T-linear term, gamma, markedly increases with Zn- or Ga-content. The gamma/gamma(N) vs. T-C/T-C0, relation for Zn-doped samples with x greater than or equal to 0.2 is in good agreement with the theoretical curve for resonant impurity scattering in a d-wave superconductor, while those for Ga-doped samples and for Zn-doped samples with x<0.2 deviate slightly from the theoretical curve. Such a deviation will be discussed in relation to the change in the magnetic properties of the present system caused by impurity-doping.
• Magnetic susceptibility of superconducting La2-xSrxCuO4

  T Nakano, N Momono, C Manabe, Y Miura, M Oda, M Ido

  CZECHOSLOVAK JOURNAL OF PHYSICS 46 1153 - 1154 1996年 [査読有り][通常論文]
   

  The T-dependent part of magnetic susceptibility chi, chi(F)(s)(T), for La2-xSrxCuO4 (0.08<x<0.2) follows a scaling law. The chi-T curve given by the sum of chi(F)(s)(T) and a constant term, related to the Pauli paramagnetism of the present system, is consistent with the spin part of Knight shift for Cu-63 nuclei over a wide variety of Sr-content, including an x-range above x similar to 0.2. The T-dependence of chi for x>0.2, showing Curie-like behavior at low temperatures, can be reproduced by a combination of a Curie term and a T-dependent term chi(F)(s)(T) which follows the scaling law as that for 0.08<x<0.2. The Curie term increases with increasing x above x similar to 0.2 where T-c is strongly suppressed, but it is corroborated by specific heat experiments that pair-breaking due to the local magnetic moments is not the dominant origin of the strong suppression of T-c for x>0.2.
• STM IMAGES AND STS OF BI2SR2CACU2O8+DELTA

  C MANABE, M ODA, M IDO

  PHYSICA C 235 797 - 798 1994年12月 [査読有り][通常論文]
   

  Clear atomic images of Bi2Sr2CaCu2O8+delta cleaved surfaces were observed al 4.2 K and 300 K by using scanning tunneling microscopy (STM). The atomic image taken under bias voltages much lower than the semiconducting gap of the Bi-O plane is of a square-lattice, which seems to be of the Cu-O plane. A modulation structure along the b-axis is seen as the change in brightness with the period of similar to 5 atomic intervals. The tunneling spectrum at 4.2 K is almost the same in both relatively bright and dark regions of the modulation structure, and in qualitative agreement with that of a gapless superconductor.
• Low-temperature electronic specific heat of La2-xSrxCuO4 and La2-xSrxCu1-yZnyO4. Evidence for a d wave superconductor

  N. Momono, M. Ido, T. Nakano, M. Oda, Y. Okajima, K. Yamaya

  Physica C: Superconductivity and its applications 233 3-4 395 - 401 1994年11月20日 [査読有り][通常論文]
   

  The electronic specific heat Cel was studied at T ≤ 10 K both on La2-xSrxCuO4 samples and on La2-xSrxCu1-yO4 samples below and above yc at which the superconductivity disappears. In superconducting La2-ySrxCuO4 samples, the Cel contains only a T2 component at T «Tc in a x range between 0.14 and 0.22, suggesting a gapless superconductor with line nodes. A T linear component of Cel appears in superconducting La2-xSrxCu1-yZnyO4 (y < yc samples, and its coefficient, γ, increases markedly with Zn content. In samples with various Zn contents, the relation between Tc/Tc (y = 0) and γ/γ(y≥yc) can be understood in terms of strong impurity scattering in a d wave superconductor. © 1994.
• LOW-TEMPERATURE ELECTRONIC SPECIFIC-HEAT OF LA2-XSRXCUO4 AND LA2-XSRXCU1-YZNYO(4)

  N MOMONO, M IDO, T NAKANO, M ODA, Y OKAJIMA, K YAMAYA

  PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 233 3-4 395 - 401 1994年11月 [査読有り][通常論文]
   

  The electronic specific heat C-e1 was studied at T less than or equal to 10 K both on La2-xSrxCuO4 samples and on La2-xSrxCu1-yZnyO4 samples below and above y(c) at which the superconductivity disappears. In superconducting La2-xSrxCuO4 samples, the C-e1 contains only a T-2 component at T << T-c in a x range between 0.14 and 0.22, suggesting a gapless superconductor with line nodes. A T linear component of C-e1 appears in superconducting La2-xSrxCu1-yZnyO4 (y<y(c)) samples, and its coefficient, y, increases markedly with Zn content. In samples with various Zn contents, the relation between T-c/T-c(y=0) and y/y(y greater than or equal to y(c)) can be understood in terms of strong impurity scattering in a d wave superconductor.
• MAGNETIC-PROPERTIES AND ELECTRONIC CONDUCTION OF SUPERCONDUCTING LA2-XSRXCUO4

  T NAKANO, M ODA, C MANABE, N MOMONO, Y MIURA, M IDO

  PHYSICAL REVIEW B 49 22 16000 - 16008 1994年06月 [査読有り][通常論文]
   

  Magnetic susceptibility chi and resistivity were measured in La2-xSrxCuO4. Enhancement of chi due to a ferromagnetic correlation, which is inherent in the orthorhombic phase at low Sr concentrations, disappears at around x = 0.05, near the margin of the superconducting regime. In superconducting samples with 0.1 less than or similar x less than or similar 0.2, chi exhibits a broad peak at a temperature T(max). The T-dependent part of chi, chi(s)(T), follows a single curve F regardless of x when chi(s) and T are normalized with the peak value chi(max)s and T(max), as has been reported. However, the present scaling curve F decreases much more at T much less than T(max) than the reported one. The resistivity exhibits a T-linear dependence above a temperature T* and deviates downward from the T-linear dependence below T*. For x > 0.1 the temperature T* agrees well with T(max), indicating that the deviation from a T-linear resistivity is related to the decrease of chi below T(max). On the other hand, for x < 0.1 a large reduction of chi is seen below approximately T* in the data up to 1000 K by Yoshizaki et al., although no peak is seen in the chi-T curve. The T dependence of chi in La2-xSrxCu1-yZnyO4 is also reported for x = 0.16 and 0.22.
• Magnetic properties and electronic conduction of superconducting La2-xSrxCuO4

  T. Nakano, M. Oda, C. Manabe, N. Momono, Y. Miura, M. Ido

  Physical Review B 49 22 16000 - 16008 1994年 [査読有り][通常論文]
   

  Magnetic susceptibility χ and resistivity were measured in La2-xSrxCuO4. Enhancement of χ due to a ferromagnetic correlation, which is inherent in the orthorhombic phase at low Sr concentrations, disappears at around x=0.05, near the margin of the superconducting regime. In superconducting samples with 0.1x0.2, χ exhibits a broad peak at a temperature Tmax. The T-dependent part of χ, χs(T), follows a single curve F regardless of x when χs and T are normalized with the peak value χmaxs and Tmax, as has been reported. However, the present scaling curve F decreases much more at TTmax than the reported one. The resistivity exhibits a T-linear dependence above a temperature T* and deviates downward from the T-linear dependence below T*. For x> 0.1 the temperature T* agrees well with Tmax, indicating that the deviation from a T-linear resistivity is related to the decrease of χ below Tmax. On the other hand, for x< 0.1 a large reduction of χ is seen below ∼T* in the data up to 1000 K by Yoshizaki et al., although no peak is seen in the χ-T curve. The T dependence of χ in La2-xSrxCu1-yZnyO4 is also reported for x=0.16 and 0.22. © 1994 The American Physical Society.
• MAGNETIC DEPAIRING IN HIGHLY-DOPED LA2CUO4

  M ODA, T NAKANO, Y KAMADA, M IDO

  PHYSICA C 185 1157 - 1158 1991年12月 [査読有り][通常論文]
   

  The magnetic susceptibility-chi of La2-xSrxCuO4 was measured in the range x congruent-to 0.06 to 0.3. The T-dependent part chi-s(T) of chi below x congruent-to 0.18 consists of a term chi-F(s)(T) arising from antiferromagnetically correlated Cu-spins, while chi-s(T) above x congruent-to 0.18 consists of chi-F(s)(T) and a Curie term which is small but grows with increasing x. The superconducting transition temperature decreases rapidly with increasing x above x congruent-to 0.18 where the Curie term appears.
• PRESSURE EFFECT ON SUPERCONDUCTIVITY AND LOW-TEMPERATURE PHASE-TRANSITION IN BA-DOPED LA2CUO4

  M IDO, N YAMADA, M ODA, Y SEGAWA, N MOMONO, A ONODERA, Y OKAJIMA, K YAMAYA

  PHYSICA C 185 911 - 912 1991年12月 [査読有り][通常論文]
   

  The diamagnetism of superconductivity and the resistivity were measured on (La1-xBax)2CuO4 under pressures up to 20 kbar. It was confirmed that the superconducting transition temperature T(c) is markedly restored as the resistive increment associated with the phase transition to a low-temperature tetragonal structure is suppressed under high pressures.
• LOW-TEMPERATURE CRYSTAL-STRUCTURE AND SUPERCONDUCTIVITY IN LA2-XBAXCUO4

  N MOMONO, M IDO, M ODA, N YAMADA, A ONODERA, Y OKAJIMA, K YAMAYA

  PHYSICA C 183 4-6 241 - 246 1991年11月 [査読有り][通常論文]
   

  The low-temperature crystal structure of La2-xBaxCuO4 (x = 0.088 approximately 0.14) was investigated by measurements of X-ray diffraction and thermal expansion. Parts of the crystal undergo a structural change at T1 congruent-to 30-60 K but the other parts remain in the mid-temperature orthorhombic (OMT) structure down to 5 K, as was already reported. It was confirmed that both parts of the crystal exhibit superconductivity although T(c) associated with the structure appearing below T1 was markedly depressed around x = 0. 125. In the parts exhibiting the structural change at T1, the CuO6 octahedra rotate both about the (110) axis and about the (1-10) axis coherently but their rotational angles differ slightly. The difference of the rotational angles seems to be closely related to the degree of the depression of T(c).
• ELECTRONIC STATES OF DOPED HOLES AND MAGNETIC-PROPERTIES IN LA2-XMXCUO4 (M = SR, BA)

  M ODA, T NAKANO, Y KAMADA, M IDO

  PHYSICA C 183 4-6 234 - 240 1991年11月 [査読有り][通常論文]
   

  The magnetic susceptibility-chi and resistivity-rho were examined in La2-xMxCuO4 (M = Sr, Ba). The T-dependent part chi(s) of chi below x congruent-to x(c) (x(c) = 0.15 and 0.18 for M = Ba and Sr) consists of a term arising from antiferromagnetically correlated Cu-spins chi(F)s (T), which is characterized by a broad peak at T(max). On the other hand, chi(s) above x = x(c) consists of chi(F)s (T) and a Curie term (C/T which is small but grows with increasing x. The superconducting transition temperature T(c) decreases rapidly with increasing x above x(c). The relation between T(c) and C can be explained in terms of the magnetic depairing due to local moments. T(max) and the g-value of the Cu-spins are almost constant above x congruent-to 0.2, although these are strongly x-dependent for x < 0.2. This fact suggests that holes doped over the concentration p congruent-to 0.2 go onto electronic states which differ large y in character from those below p congruent-to 0.2. It is also found that a significant change in the rho-T curve occurs at x congruent-to 0.2.
• MAGNETIC BEHAVIORS AND THEIR EFFECTS ON THE CONDUCTIVITY IN SINGLE-CRYSTAL LA2CUO4

  M ODA

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 60 1 235 - 244 1991年01月 [査読有り][通常論文]
   

  Magnetic behaviors and their effects on the conductivity are examined in the Neel state (T(N) congruent-to 210 K) of La2CuO4 single crystals. The magnetization jump at a field-induced weak ferromagnetic (WF) transition and the critical field exhibit the same T-dependence as the sublattice moment. The magnetoresistance DELTA-R, observed at the WF transition, takes a small positive value down to approximately 110 K (T*), while for T less-than-or-similar-to T*, DELTA-R is negative and its magnitude increases drastically with lowering T. At T*, a magnetic transition is also observed; it is accompanied by a large decrease of hopping conductivity due to an enhancement of Anderson localization. It is shown that the large negative delta-R for T less-than-or-similar-to T * is due to the increase of the carrier mobility, which arises from the fac t that the enhancement of Anderson localization below T* is largely suppres sed by the spin structure change at the WF transition.
• LOW-TEMPERATURE TETRAGONAL PHASE AND ELECTRONIC COEFFICIENT OF SPECIFIC-HEAT IN (LA1-XBAX)2CUO4

  Y OKAJIMA, K YAMAYA, M ODA, M IDO

  PHYSICA B 165 1349 - 1350 1990年08月 [査読有り][通常論文]
  
• COMMON FEATURES OF MAGNETIC AND SUPERCONDUCTING PROPERTIES IN Y-DOPED BI2(SR,CA)3CU2O8 AND BA(SR)-DOPED LA2CUO4

  M ODA, H MATSUKI, M IDO

  SOLID STATE COMMUNICATIONS 74 12 1321 - 1326 1990年06月 [査読有り][通常論文]
  
• REDUCTION OF THE ELECTRONIC COEFFICIENT OF THE SPECIFIC-HEAT AROUND X=0.065 IN (LA1-XBAX)2CUO4

  Y OKAJIMA, K YAMAYA, N YAMADA, M ODA, M IDO

  SOLID STATE COMMUNICATIONS 74 8 767 - 771 1990年05月 [査読有り][通常論文]
  
• MAGNETISM AND SUPERCONDUCTIVITY IN DOPED LA2CUO4

  M ODA, T OHGURO, H MATSUKI, N YAMADA, M IDO

  PHYSICAL REVIEW B 41 4 2605 - 2607 1990年02月 [査読有り][通常論文]
  
• Magnetism and superconductivity in doped La2CuO4

  M. Oda, T. Ohguro, H. Matsuki, N. Yamada, M. Ido

  Physical Review B 41 4 2605 - 2608 1990年 [査読有り][通常論文]
   

  The temperature (T) dependence of magnetic susceptibility () in (La1-xMx)2CuO4 (M=Sr,Ba) is examined for T< 580 K. A broad peak (max) in the -T curve, already reported for a Sr-doped system, is also observed in a Ba-doped one. The temperature exhibiting max decreases with a linear dependence on x and tends rapidly to zero at around x=xc (xc0.12 for M=Sr and 0.1 for M=Ba). For xxc, the monotonically increases with lowering T over the entire T range examined. In both systems, the superconductivity is found to be remarkably suppressed above xc.. AE © 1990 The American Physical Society.
• PRESSURE EFFECT ON THE LOW-TEMPERATURE TETRAGONAL PHASE AND THE SUPERCONDUCTIVITY IN (LA1-XBAX)2CUO4

  N YAMADA, M ODA, M IDO, Y OKAJIMA, K YAMAYA

  SOLID STATE COMMUNICATIONS 70 12 1151 - 1153 1989年06月 [査読有り][通常論文]
  
• ANTIFERROMAGNETIC SPIN CORRELATIONS IN INSULATING, METALLIC, AND SUPERCONDUCTING LA2-XSRXCUO4

  RJ BIRGENEAU, DR GABBE, HP JENSSEN, MA KASTNER, PJ PICONE, TR THURSTON, G SHIRANE, Y ENDOH, M SATO, K YAMADA, Y HIDAKA, M ODA, Y ENOMOTO, M SUZUKI, T MURAKAMI

  PHYSICAL REVIEW B 38 10 6614 - 6623 1988年10月 [査読有り][通常論文]
  
• Neutron Powder Diffraction from Polymorphs of BaPb0.75Bi0.25O3

  Asano Hajime, Oda Migaku, Endoh Yasuo, Hidaka Yoshikazu, Izumi Fujio, Ishigaki Tōru, Karahashi Kazuhiro, Murakami Toshiaki, Watanabe Noboru

  Jpn J Appl Phys 27 9 1638 - 1640 社団法人応用物理学会 1988年09月20日 

  Crystal structures of three polymorphs of the superconducting oxide BaPb0.75Bi0.25O3 have been determined by high-resolution neutron powder diffraction. The compound has been confirmed to form both tetragonal (I4/mcm) and orthorhombic (Ibmm) structures at room temperature. The latter transforms to the monoclinic phase (P21/m) at low temperatures. The structural difference of the three polymorphs has been described by the rotation as well as the distortion of oxygen octahedra surrounding the Pb0.75Bi0.25 cations.
• TWO-DIMENSIONAL ZONE-CENTER SPIN-WAVE EXCITATIONS IN LA2CUO4

  CJ PETERS, RJ BIRGENEAU, MA KASTNER, H YOSHIZAWA, Y ENDOH, J TRANQUADA, G SHIRANE, Y HIDAKA, M ODA, M SUZUKI, T MURAKAMI

  PHYSICAL REVIEW B 37 16 9761 - 9764 1988年06月 [査読有り][通常論文]
  
• COMPARISON BETWEEN MUON SPIN ROTATION AND NEUTRON-SCATTERING STUDIES ON THE 3-DIMENSIONAL MAGNETIC-ORDERING OF LA2CUO4-Y

  YJ UEMURA, WJ KOSSLER, KEMPTON, JR, XH YU, HE SCHONE, D OPIE, CE STRONACH, JH BREWER, RF KIEFL, KREITZMAN, SR, GM LUKE, T RISEMAN, DL WILLIAMS, EJ ANSALDO, Y ENDOH, E KUDO, K YAMADA, DC JOHNSTON, M ALVAREZ, DP GOSHORN, Y HIDAKA, M ODA, Y ENOMOTO, M SUZUKI, T MURAKAMI

  PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 153 769 - 770 1988年06月 [査読有り][通常論文]
  
• STATIC AND DYNAMIC SPIN CORRELATIONS IN PURE AND DOPED LA2CUO4

  Y ENDOH, K YAMADA, RJ BIRGENEAU, DR GABBE, HP JENSSEN, MA KASTNER, CJ PETERS, PJ PICONE, TR THURSTON, JM TRANQUADA, G SHIRANE, Y HIDAKA, M ODA, Y ENOMOTO, M SUZUKI, T MURAKAMI

  PHYSICAL REVIEW B 37 13 7443 - 7453 1988年05月 [査読有り][通常論文]
  
• LARGE ANISOTROPY OF THE UPPER CRITICAL MAGNETIC-FIELD IN SINGLE-CRYSTAL BI-(SR,CA)-CU-O

  Y HIDAKA, M ODA, M SUZUKI, Y MAEDA, Y ENOMOTO, T MURAKAMI

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 27 4 L538 - L541 1988年04月 [査読有り][通常論文]
  
• Two-dimensional zone-center spin-wave excitations in La2CuO4

  C. J. Peters, R. J. Birgeneau, M. A. Kastner, H. Yoshizawa, Y. Endoh, J. Tranquada, G. Shirane, Y. Hidaka, M. Oda, M. Suzuki, T. Murakami

  Physical Review B 37 16 9761 - 9764 1988年 [査読有り][通常論文]
   

  We have studied the spin-wave excitations near the two-dimensional zone center at 80 K in a single crystal of La2CuO4 which orders at TN=195 K. In-plane and out-of-plane modes are observed at energies of 1.0±0.25 meV and 2.5±0.5 meV, respectively, The in-plane mode energy is determined primarily by the antisymmetric exchange and it measures this term directly. The out-of-plane mode energy corresponds to a planar anisotropy energy of 1/40.016 meV. We observe, in addition, the appearance of significant E0 scattering below 30 K. © 1988 The American Physical Society.
• Effect of Heat Treatment on the Low-Temperature NQR Spectrum of ¹³⁹La in Single Crystals and Polycrystals of the Antiferromagnetic La2CuO4

  Hironori Nishihara, Nobuyuki Sugii, Yoshikazu Hidaka, Migaku Oda, Tadashi Shimizu, Hiroshi Yasuoka, Keiichi Koga, Kohji Kishio, Koichi Kitazawa, Kazuo Fueki, Minoru Suzuki, Toshiaki Murakami, Tsukio Ohtani

  Journal of the Physical Society of Japan 57 4 1159 - 1162 1988年 [査読有り][通常論文]
   

  Zero-field nuclear quadrupole resonance (NQR) spectra of 139La are examined at 1.3 K for single crystals and polycrystals of the antiferromagnetic La2CuO4 which have been subject to heat treatments of oxygenation or deoxygenation. Although the Néel temperature (TN) determined from the static susceptibility strongly depends on the heat treatments, the peak positions of the NQR spectrum at 1.3 K are invariant against the heat treatments for samples with TN between 135 and 305 K, suggesting that the sublattice moment of the Cu spins at low temperatures is invariant against the heat treatments. A simple oxygen-deficient model described by La2CuO4–δ is found to be inadequate from observed effects of the heat treatments on the line widths of the NQR spectrum. © 1988, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.
• Electric Properties of La2CuO4-y

  M. Oda, Y. Hidaka, M. Suzuki, Y. Enomoto, T. Murakami, K. Yamada, Y. Endoh

  Solid State Communications 67 3 257 - 261 1988年 [査読有り][通常論文]
   

  The resistivity of La2CuO4 was reexamined for single crystals grown by the CuO flux method as well as single crystalline thin films epitaxially grown on the SrTiO3 substrate. We observed a noticiable anisotropy and a two dimensional variable-range-hopping (VRH) behavior. These features differ a little from the results by Kastner et al., who first presented the VRH behavior for the crystal. © 1988.
• Anisotropic superconducting properties of Ba2YCu3O7-y

  M. Oda, Y. Hidaka, M. Suzuki, T. Murakami

  Physical Review B 38 1 252 - 256 1988年 [査読有り][通常論文]
   

  The upper critical magnetic field Hc2 of Ba2YCu3O7-y single crystals is estimated from the resistive transition curves as a function of temperature and field direction. Hc2 exhibits a large anisotropy between the c axis and the a-b plane. The Hc2 data have linear temperature dependence, giving well-defined dHc2dT values: -0.56 T/K for the c axis and -3.3 T/K for the a-b plane. The angular dependence of Hc2 is in good agreement with the effective-mass model when the ratio MM =60, which is comparable to resistivity anisotropy in the normal state. On the other hand, no signs of anisotropy in the a-b plane can be recognized. This indicates that supercurrent flows dominantly in the Cu-O sheets, and that the Cu-O chains with oxygen deficiency are less conductive. © 1988 The American Physical Society.
• ANISOTROPIC UPPER CRITICAL MAGNETIC-FIELD IN SINGLE-CRYSTAL BA2YCU3O7-Y

  Y HIDAKA, M ODA, M SUZUKI, A KATSUI, T MURAKAMI, N KOBAYASHI, Y MUTO

  PHYSICA B & C 148 1-3 329 - 331 1987年12月 [査読有り][通常論文]
  
• ANISOTROPIC PROPERTIES OF EPITAXIAL BA2YCU3O7-Y THIN-FILMS

  Y ENOMOTO, M SUZUKI, M ODA, T MURAKAMI

  PHYSICA B & C 148 1-3 408 - 410 1987年12月 [査読有り][通常論文]
  
• ANISOTROPIC OPTICAL-PROPERTIES OF (LA1-XSRX)2CUO4 SINGLE-CRYSTAL THIN-FILMS

  M SUZUKI, M ODA, Y ENOMOTO, T MURAKAMI

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 26 12 L2052 - L2054 1987年12月 [査読有り][通常論文]
  
• SUPERCONDUCTIVITY IN IMPURITY-INDUCED TETRAGONAL YBA2(CU1-XFEX)3O7-DELTA

  Y MAENO, M KATO, Y AOKI, T FUJITA

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 26 12 L1982 - L1984 1987年12月 [査読有り][通常論文]
  
• SINGLE-CRYSTAL GROWTH OF (LA1-XBAX)2CUO4 OR(LA1-XSRX)2CUO4 AND BA2YCU3O7-Y

  Y HIDAKA, Y ENOMOTO, M SUZUKI, M ODA, T MURAKAMI

  JOURNAL OF CRYSTAL GROWTH 85 4 581 - 584 1987年12月 [査読有り][通常論文]
  
• THE EFFECT OF THE HEAT-TREATMENTS ON THE ANTIFERROMAGNETISM IN LA2CUO4-DELTA SINGLE-CRYSTALS

  K YAMADA, E KUDO, Y ENDOH, Y HIDAKA, M ODA, M SUZUKI, T MURAKAMI

  SOLID STATE COMMUNICATIONS 64 5 753 - 756 1987年11月 [査読有り][通常論文]
  
• TWO-DIMENSIONAL ANTIFERROMAGNETIC QUANTUM SPIN-FLUID STATE IN LA2CUO4

  G SHIRANE, Y ENDOH, RJ BIRGENEAU, MA KASTNER, Y HIDAKA, M ODA, M SUZUKI, T MURAKAMI

  PHYSICAL REVIEW LETTERS 59 14 1613 - 1616 1987年10月 [査読有り][通常論文]
  
• SPACE-GROUP DETERMINATION OF LA2CUO4-DELTA BY CONVENTIONAL AND CONVERGENT-BEAM ELECTRON-DIFFRACTION

  M TANAKA, K TSUDA, K YAMADA, Y ENDOH, Y HIDAKA, M ODA, M SUZUKI, T MURAKAMI

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 26 9 L1502 - L1504 1987年09月 [査読有り][通常論文]
  
• NONLINEAR CONDUCTIVITY DUE TO FIELD-INDUCED DEPINNING OF CHARGE-DENSITY WAVES IN NBSE3

  M IDO, Y OKAJIMA, H WAKIMOTO, M ODA

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 56 7 2503 - 2510 1987年07月 [査読有り][通常論文]
  
• OXYGEN DEFICIENCY IN YBA2CU3O7+Y, YSR2CU3O7+Y FAMILY

  M ODA, T MURAKAMI, Y ENOMOTO, M SUZUKI

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 26 5 L804 - L806 1987年05月 [査読有り][通常論文]
  
• ANISOTROPY OF THE UPPER CRITICAL MAGNETIC-FIELD IN SINGLE-CRYSTAL YBA2CU3O7+Y

  Y HIDAKA, Y ENOMOTO, M SUZUKI, M ODA, A KATSUI, T MURAKAMI

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 26 5 L726 - L728 1987年05月 [査読有り][通常論文]
  
• ANISOTROPIC PROPERTIES OF SUPERCONDUCTING SINGLE-CRYSTAL (LA1-XSRX)2CUO4

  Y HIDAKA, Y ENOMOTO, M SUZUKI, M ODA, T MURAKAMI

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 26 4 L377 - L379 1987年04月 [査読有り][通常論文]
  
• STRUCTURE AND ELECTRICAL-PROPERTIES OF SUPERCONDUCTING BAPB1-XBIXO3

  Y ENOMOTO, M ODA, T MURAKAMI

  PHASE TRANSITIONS 8 2 129 - 146 1987年 [査読有り][通常論文]
  
• SUPERCONDUCTIVITY IN YBA2CU3O7-DELTA, YSR2CU3O7-DELTA FAMILY

  M ODA, T MURAKAMI, Y ENOMOTO, M SUZUKI

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 26 1053 - 1054 1987年 [査読有り][通常論文]
  
• ANISOTROPIC PROPERTIES OF SUPERCONDUCTING SINGLE-CRYSTALS (LA1-XSRX)2CUO4 AND BA2YCU3O7+Y

  Y HIDAKA, Y ENOMOTO, M SUZUKI, M ODA, A KATSUI, T MURAKAMI

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 26 1133 - 1134 1987年 [査読有り][通常論文]
  
• THE CRYSTALLOGRAPHIC SYMMETRIES OF SINGLE BAPB1-XBIXO3 CRYSTALS GROWN FROM BACO3-PBO2-BI2O3 SOLUTIONS

  M ODA, Y HIDAKA, A KATSUI, T MURAKAMI

  SOLID STATE COMMUNICATIONS 60 12 897 - 900 1986年12月 [査読有り][通常論文]
  
• DIRECT OBSERVATION OF CONDUCTION NOISE UNDER PULSED ELECTRIC-FIELD IN THE NONOHMIC REGIME OF NBSE3

  M IDO, Y OKAJIMA, H WAKIMOTO, M ODA

  PHYSICA B & C 143 1-3 54 - 58 1986年11月 [査読有り][通常論文]
  
• Direct observation of conduction noise under pulsed electric field in the nonohmic regime of NbSe3

  Masayuki Ido, Yoshitoshi Okajima, Hirotsugu Wakimoto, Migaku Oda

  Physica B+C 143 1-3 54 - 58 1986年 [査読有り][通常論文]
   

  Oscillatory response of the charge-density wave (CDW) to repetitive pulsed fields was investigated in the q2-CDW regime of NbSe3. Crystals used exhibit the narrow band noise with only one fundamental component under a dc bias. We find in such crystals that the oscillation ceases at its top (bottom), regardless of the pulse width, at relatively low fields and the number of oscillations observed within the pulse width is always integral. Such a singular oscillatory response, which appears to contradict with causality, is considered to be ascribed to some kind of memory effect in metastable states of the CDW. It is also found that during a pulsed field the CDW moves coherently over the whole sample volume by integral multiples of the q2-CDW wave length. © 1986.
• 2p-B-9 BaPb_<1-x>Bi_xO_3単結晶薄膜の電気的・光学的特性

  仙場 浩一, 小田 研, 森脇 和幸, 鈴木 実, 村上 敏明

  秋の分科会予稿集 1985 212 - 212 一般社団法人 日本物理学会 1985年
• STRUCTURAL PHASE-TRANSITION IN SUPERCONDUCTING BAPB0.75BI0.25O3

  M ODA, Y HIDAKA, A KATSUI, T MURAKAMI

  SOLID STATE COMMUNICATIONS 55 5 423 - 426 1985年 [査読有り][通常論文]
  
• TRANSIENT CONDUCTIVITY AND CONDUCTION NOISE IN NBSE3

  M ODA, M IDO

  SOLID STATE COMMUNICATIONS 50 10 879 - 884 1984年 [査読有り][通常論文]
  
• CHARGE-DENSITY-WAVE CONDUCTIVITY IN NBSE3

  M ODA, M IDO

  SOLID STATE COMMUNICATIONS 44 12 1535 - 1538 1982年 [査読有り][通常論文]
  

講演・口頭発表等

• Correlation between electronic state and magnetism in La2CuO4+d

  K. Miyakoshi, K. Tachi, M. Iwamatsu, Y. Kinugawa, S. Mizuta, H. Yoshida, Y. Ihara, Y. Toda, T. Kurosawa, N. Momono, M. Oda

  International Conference on Quantum Liquid Crystals 2023 2023年08月 ポスター発表
• 少量の過剰酸素が添加された La 系銅酸化物の磁場中における 超伝導および超伝導揺らぎ

  岩松柾希, 宮腰宏太, 城剛希, 衣川裕也, 水田崇聖, 井原慶彦, 吉田紘行, 戸田泰則, 黒澤徹, 桃野直樹, 小田研

  日本物理学会2023年春季大会 2023年03月 口頭発表（一般）
• 少量の過剰酸素が添加されたLa系銅酸化物の電気伝導と磁気秩序の関わり

  宮腰宏太, 城剛希, 岩松柾希, 衣川裕也, 水田崇聖, 井原慶彦, 吉田紘行, 戸田泰則, 黒澤徹, 桃野直樹, 小田研

  日本物理学会2023年春季大会 2023年03月 口頭発表（一般）
• Effects of magnetic order on electronic conduction in high-Tc cuprate La2CuO4+d

  K. Miyakoshi, M. Iwamatsu, K. Tachi, Y. Kinugawa, S. Mizuta, Y. Ihara, H. Yoshida, Y. Toda, T. Kurosawa, N. Momono, and M, Oda

  International workshop on Microscopic Properties of Quantum Materials 2022年08月 ポスター発表
• La-NQR測定による過剰酸素La2CuO4+yにおいて実現する超伝導―反強磁性共存状態の微視的研究

  井原慶彦, 衣川裕也, 小田研

  日本物理学会 第77回年次大会 2022年03月 口頭発表（一般）
• STM/STSからみたBi2212の電子系変調構造とエネルギーギャップ

  水田 崇聖, 黒澤 徹, 吉田 紘行, 小田 研, 伊土 政幸, 桃野 直樹

  日本物理学会 第75回年次大会 2020年03月 口頭発表（一般）
• 銅酸化物高温超伝導体におけるチェッカーボード変調と準粒子干渉との実空間相関

  小田 研, 水田 崇聖, 黒澤 徹, 吉田 紘行, 伊土 政幸, 桃野 直樹, 戸田 泰則

  つくば-柏-本郷 超伝導かけはしプロジェクト・ワークショップ 2020年01月 口頭発表（一般）
• STM/STS studies on electronic modulations in high-Tc cuprate Bi2212  [招待講演]

  Migaku Oda

  International Conference on Quantum Physics in Complex Matter: Superconductivity, Magnetism and Ferroelectricity 2019年06月 口頭発表（招待・特別）
• 銅酸化物高温超伝導体Bi2212の 超伝導ギャップと一次元超格子との相関  [通常講演]

  小田 研

  つくば-柏-本郷 超伝導かけはしプロジェクト ワークショップ 2019年01月 口頭発表（一般）
• STM imaging of electronic superstructures in high-Tc cuprate Bi2Sr2CaCu2O8+d  [招待講演]

  M. Oda, S. Mizuta, T. Kurosawa, H. Yoshida, M. Ido, N. Momono, Y. Toda

  ECSN2019 International Conference 2019年 口頭発表（招待・特別）
• STM/STS imaging of electronic superstructures in high-Tc cuprate Bi2212  [招待講演]

  M. Oda, S. Mizuta, T. Kurosawa, H. Yoshida, M. Ido, N. Momono, Y. Toda

  Superstripes 2019 International Conference 2019年 口頭発表（招待・特別）
• STM/STS Study on Coexistence of Electronic Superstructures in Cuprate Superconductor Bi2Sr2CaCu2O8+x  [招待講演]

  S. Mizuta, T. Kurosawa, N. Momono, H. Yoshida, M. Oda, M. Ido

  5th ISCPMS (International Symposium on Current Progress in Mathematics and Sciences) 2019年 口頭発表（招待・特別）
• Coexistence of electronic superstructures in high-Tc cuprate Bi2Sr2CaCu2O8+x studied by STM/STS  [通常講演]

  S. Mizuta, T. Kurosawa, N. Momono, H. Yoshida, M. Oda, M. Ido

  SNS (spectroscopies in Novel Superconductors) 2019 2019年 ポスター発表
• STM/STS Study on Electronic Superstructures in High-Tc Cuprate Bi2Sr2CaCu2O8+x  [通常講演]

  S. Mizuta, T. Kurosawa, N. Momono, H. Yoshida, M. Oda, M. Ido

  M2S-2018 conference 2018年08月 ポスター発表
• STM/STS studies on the electronic superlattices concerning to three kinds of energy gaps in Bi2Sr2CaCu2O8+d  [招待講演]

  Migaku Oda

  Seminar in Jožef Stefan Institute 2018年06月 公開講演，セミナー，チュートリアル，講習，講義等
• 銅酸化物高温超伝導体Bi2212の エネルギーギャップと関係する超格子構造  [通常講演]

  小田 研

  つくば-柏-本郷 超伝導かけはしプロジェクト ワークショップ 2018年03月 口頭発表（一般）
• STM/STSから⾒たBi2Sr2CaCu2O8+δにおける電⼦ 系の変調構造  [通常講演]

  水田崇聖, 黑澤徹, 竹山幸作, 桃野直樹, 吉田紘行, 小田研, 伊土政幸

  日本物理学会第73回年次大会 2018年03月 口頭発表（一般）
• STM/STS studies on energy gaps & electronic superstructures in high-Tc cuprate Bi2Sr2CaCu2O8+δ  [招待講演]

  Migaku Oda

  EMRS 2017 fall meeting 2017年09月 口頭発表（招待・特別）
• STM/STS studies on electronic superstructures in the superconducting state of high-Tc cuprate Bi2Sr2CaCa2O8+  [通常講演]

  S. Mizuta, T. Kurosawa, K. Takeyama, N. Momono, Y. Ishii, H. Yoshida, M. Oda, M. Ido

  28th International Conference on Low temperature Physics 2017年08月 ポスター発表
• STM/STS study on the spatial dependence of energy gap in high-Tc cuprate Bi2Sr2CaCu2O8+δ  [招待講演]

  Migaku Oda

  Quantum physics in Complex Matter: Superconductivity, Magnetism and Ferroelectricity 2017年06月 口頭発表（基調）
• STM/STSによる銅酸化物高温超伝導体Bi2212の局所電子状態の観察  [通常講演]

  水田崇聖, 黒澤徹, 桃野直樹, 竹山幸作, 吉田紘行, 小田研, 伊土政幸

  東京大学物性研短期研究会「走査トンネル顕微鏡による物性研究の現状と展望」 2016年10月 ポスター発表
• STM/STSから見たBi2212の電荷秩序とエネルギーギャップ  [通常講演]

  水田崇聖, 岸文香, 米川雄太, 黒澤徹, 桃野直樹, 竹山幸作, 吉田紘行, 小田研, 伊土政幸

  日本物理学会2016年秋季大会 2016年09月 口頭発表（一般）
• STM/STS studies for out-of-plane disorder effects on the charge order and pseudogap in Bi2Sr1.7R0.3CuO6+δ (R = La and Eu)  [招待講演]

  Migaku Oda

  SUPERSTRIPES 2016 2016年06月 口頭発表（招待・特別）
• Intrinsic spatial dependence of superconducting gap in high-Tc cuprate Bi2Sr2CaCa2O8+: an STM/STS study  [通常講演]

  Y. Shibata, T. Nonami, O. Urata, S. Mizuta, T. Kurosawa, Y. Toda, H. Yoshida, N. Momono, K. Takeyama, M. Oda, M. Ido

  RIKEN Symposium “Experimental and theoretical Applications of Spin-Resonance Techniques to Advanced Material Science 2016年05月 口頭発表（一般）
• STM/STS Studies for Interplane Disorder Effects on the Electronic Properties of BiBased HighTc Cuprates  [通常講演]

  M. Kataoka, Y. Shibata, T. Kurosawa, K. Takeyama, H. Yoshida, A. Kishi, Y. Yonekawa, N. Momon, M. Oda, M. Ido

  28th International Symposium on Superconductivity 2015年11月 ポスター発表
• STM/STSから見たBi2212のオーバードープ 領域におけるギャップ構造  [通常講演]

  岸文香, 米川雄太, 黒澤徹, 桃野直樹, 竹山幸作, 吉田紘行, 小田研, 伊土政幸

  日本物理学会第70回年次大会 2015年03月 口頭発表（一般）
• STM/STSから見たBi2212のアンダードープ 領域における電荷秩序と準粒子干渉  [通常講演]

  米川雄太, 板垣征一朗, 岸文香, 黒澤徹, 桃野直樹, 吉田紘行, 竹山幸作, 小田研, 伊土政幸

  日本物理学会第70回年次大会 2015年03月 口頭発表（一般）
• STM/STS Studies for interplane disorder effects on the pseudogap, electronic charge order and superconductivity in Bi2201  [招待講演]

  Migaku Oda

  International Conference on Study of matter at extreme conditions 2015年03月 口頭発表（招待・特別）
• STM/STS studies for interplane disorder effects on the pseudogap, electronic charge order and superconductivity in Bi2201  [招待講演]

  Migaku Oda

  10th International Conference on New Theories, Discoveries, Applications of Superconductors and Related Materials 2014年10月 口頭発表（招待・特別）
• STM/STSから見たアンダードープ領域におけるBi2212の電荷秩序と擬ギャップ  [通常講演]

  板垣征一朗, 黒澤徹, 米川雄太, 竹山幸作, 桃野直樹, 吉田紘行, 小田研, 伊土政幸

  日本物理学会2014年秋季大会 2014年09月 口頭発表（一般）
• STM/STSからみたBi2212の超伝導に対する Ni不純物効果  [通常講演]

  浦田理礼, 柴田悠人, 黒澤徹, 吉田紘行, 桃野直樹, 小田研, 伊土政幸

  日本物理学会2014年秋季大会 2014年09月 ポスター発表
• STM/STSから見たBi2212の1次元変調構造とギャップサイズの相関  [通常講演]

  野並拓矢, 吉田紘行, 岸文香, 黒澤徹, 戸田泰則, 竹山幸作, 小田研, 伊土政幸

  日本物理学会2014年秋季大会 2014年09月 ポスター発表
• STM/STS studies on the Fermi surface dichotomy in high-Tc cuprates: role of pseudogap & electronic charge order in high-Tc cuprate superconductivity  [招待講演]

  Migaku Oda

  International Symposium on Inhomogeneous Superconductors and Related Functional Materials 2013年03月 口頭発表（招待・特別）
• STM/STSから見た銅酸化物高温超伝導体の擬ギャップ/電荷秩序と超伝導  [招待講演]

  小田 研

  科研費新学術研究領域「超低速ミューオン顕微鏡が拓く物質・生命・素粒子科学のフロンティア」 第2回領域会議 2012年08月 口頭発表（招待・特別）
• Competition between inhomogeneous antinodal-pseudogap and homogeneous nodal-SC-gap in high-Tc cuprates: STM/STS studies on dichotomy of the Fermi surface  [招待講演]

  Migaku Oda

  International Conference on Study of matter at extreme conditions 2011年03月 口頭発表（招待・特別）
• STM/STS studies on the pseudogap, electronic charge order and superconductivity of high-Tc cuprate Bi2Sr2CaCu2O8+  [招待講演]

  Migaku Oda

  STPIPES2010 2010年07月 口頭発表（招待・特別）
• STM/STS studies on the inhomogeneous PG, electronic charge order and effective SC gap of high-Tc cuprate Bi2Sr2CaCu2O8+  [招待講演]

  Migaku Oda

  International Conference on New directions of superconducting nanostructures (NDSN2009) 2009年09月 口頭発表（招待・特別）
• Checkerboard-type electronic charge order in the pseudogap and superconducting states of high-Tc cuprate Bi2Sr2CaCu2O8+: STM/STS studies  [招待講演]

  Migaku Oda

  The 10th RIES-Hukudai international symposium 2008年12月 口頭発表（招待・特別）
• On the relation between pseudogap and SC gap in high-Tc cuprates  [招待講演]

  Migaku Oda

  21st international symposium on superconductivity (ISS’08 2008年10月 口頭発表（招待・特別）
• On the relations among pseudogap, electronic charge order and Fermi-arc superconductivity in high-Tc cuprates  [招待講演]

  Migaku Oda

  6th International Stripes Conference on High-Tc Superconductors 2008年06月 口頭発表（招待・特別）
• Pseudogap, Charge Order and Fermi-arc Superconductivity in High-Tc cuprates  [招待講演]

  Migaku Oda

  International Symposium on Lattice Effects in Cuprate High Temperature Superconductors 2007年10月 口頭発表（招待・特別）
• 銅酸化物高温超伝導体における不均一超伝導状態：擬ギャップ、電荷秩序との関連性  [招待講演]

  小田 研

  日本物理学会第62回年次大会、領域６－領域８合同シンポジウム（主題：不均一超流動・超伝 導の物理） 2007年09月 口頭発表（招待・特別）
• Fermi-arc Superconductivity, Pseudogap and Charge Order in High-Tc cuprates  [招待講演]

  Migaku Oda

  International Symposium on Inhomogeneous and Strongly-Correlated Materials with Advanced Functions 2007年04月 口頭発表（招待・特別）
• Nordal Fermi-arc Superconductivity and Anti-nodal Pseudogap in High-Tc cuprates  [招待講演]

  Migaku Oda

  International Conference on New Theories, Discoveries, Applications on Superconductors and Related Materials 2007年01月 口頭発表（招待・特別）
• Electronic Charge Order in the Pseudogap State of high-Tc cuprates  [招待講演]

  Migaku Oda

  International Workshop on Recent Developments in Low Dimensional Charge Density Wave Conductors 2006年06月 口頭発表（招待・特別）
• Role of nodal Fermi arc in the unusual orientation of square vortex-lattice in La214  [招待講演]

  Migaku Oda

  4th international conference on magnetic and superconducting materials 2005年09月 口頭発表（招待・特別）
• Nodal superconductivity in high-Tc cuprates  [招待講演]

  Migaku Oda

  SMEC conference on inhomogeneous and strongly correlated materials with novel functional properties 2005年03月 口頭発表（招待・特別）
• Role of Nodal Fermi arc in high-Tc superconductivity  [招待講演]

  Migaku Oda

  International Workshop on Electron States and lattice Effects in Cuprate High Temperature Superconductors 2005年 口頭発表（招待・特別）
• Dip feature of electronic excitation spectra in the superconducting state of Bi2212  [招待講演]

  Migaku Oda

  4th International Stripes Conference on High-Tc Superconductors 2004年 口頭発表（招待・特別）
• Electronic excitations in the superconducting state of Bi2212  [招待講演]

  Migaku Oda

  International Conference on Nanoscale Properties of Condensed Matter Probed by Resonance Phenomena 2004年 口頭発表（招待・特別）
• Electronic excitation spectra near Tc in Bi2212: a tunneling study  [招待講演]

  Migaku Oda

  International Symposium on Emerging Mechanisms for High-Tc Superconductivity 2004年 口頭発表（招待・特別）
• Drastic changes in Electronic Excitations across Tc in Bi2212  [招待講演]

  Migaku Oda

  4th Int’l Conf. on New Theories, Discoveries and Applications of Superconductors and Related Materials 2003年 口頭発表（招待・特別）
• Tunneling studies on the electronic excitation spectrum of Bi2212  [招待講演]

  Migaku Oda

  SMEC Conf. on Inhomogeneous and Strongly Correlated Materials with Novel Electronic Properties 2003年 口頭発表（招待・特別）
• Electronic Excitation Spectrum in the Superconducting State of Bi2212  [招待講演]

  Migaku Oda

  Int’l Conf. on Dynamic Inhomogeneities in Complex Oxides 2003年 口頭発表（招待・特別）
• Electronic Phase Diagram of High-Tc cuprates  [招待講演]

  Migaku Oda

  Int’l Conf. on Quantum Transport in Synthetic Metals and Quantum Functional Semiconductors 2003年 口頭発表（招待・特別）
• Energy gap evolution in Bi2212: an STM tunneling study  [招待講演]

  Migaku Oda

  International Conference on Superconductivity, SCRM 2002 2002年06月 口頭発表（招待・特別）
• Tunneling studies on the energy gap evolution of Bi2212  [招待講演]

  Migaku Oda

  SPIE int’l symposium on superconductivity and related oxides: physics and Nanoengineering IV 2002年 口頭発表（招待・特別）
• Energy gap evolution as functions of temperature and doping in Bi2212  [招待講演]

  Migaku Oda

  Int’l Conf. on Modern Problems of Superconductivity 2002年 口頭発表（招待・特別）
• Energy gap evolution and electronic phase diagram in high-Tc cuprates: an STM tunneling study  [招待講演]

  Migaku Oda

  APCTP/ICTP joint international Ssymposium on the condensed matter theory 2002年 口頭発表（招待・特別）
• STM observations of single and pair tunneling on Bi2212: pseudogap and effective SC gap  [招待講演]

  Migaku Oda

  Lorentz center workshop on strongly correlated electron systems 2001年09月 口頭発表（招待・特別）
• Temperature evolution of energy gap studied by tunneling techniques in Bi2212  [招待講演]

  Migaku Oda

  Third international conference on new theories, discoveries and applications of superconductors and related materials 2001年 口頭発表（招待・特別）
• What is the energy scale in determining the Tc of cuprate superconductivity?  [招待講演]

  Migaku Oda

  The sixth international workshop “high temperature superconductors and novel inorganic materials engineering” 2001年 口頭発表（招待・特別）
• Superconducting gap and pseudogap in BSCCO and LSCO  [招待講演]

  Migaku Oda

  Int’l workshop on networks and nanoscale coherence in 2D Metals and HTSC 2001年 口頭発表（招待・特別）
• Novel relation between Tc and energy gap in Bi2212 and La214: an STM/STS Study  [招待講演]

  Migaku Oda

  6th international conference on materials and mechanisms of superconductivity and high- temperature superconductors 2000年02月 口頭発表（招待・特別）
• Energy scale in determining Tc of cuprate superconductors  [招待講演]

  Migaku Oda

  SPIE international symposium on superconductivity and related oxides: physics and Nanoengineering IV 2000年 口頭発表（招待・特別）
• STM/STS study on the relation between low-temperature gap amplitude 0 and Tc in high-Tc cuprates  [招待講演]

  Migaku Oda

  The 5th POSTECH Workshop on strongly correlated electron systems and quantum field theory 1999年 口頭発表（招待・特別）
• Superconducting gap in tunneling spectra and pseudogap behavior in magnetic susceptibility on high-Tc cuprates  [招待講演]

  Migaku Oda

  Second international conference on new theories, discoveries and applications of superconductors and related materials 1999年 口頭発表（招待・特別）
• Superconducting gap in the tunneling spectra of high-Tc cuprates: evidence for the strong connection between pseudogap behavior and superconductivity  [招待講演]

  Migaku Oda

  First international conference on new theories, discoveries and applications of superconductors and related materials 1998年 口頭発表（招待・特別）
• 高温超伝導体の擬ギャップと超伝導  [招待講演]

  小田 研

  日本物理学会低温分科会シンポジウム 1997年 口頭発表（招待・特別）
• Pseudogap in the quasiparticle density of states in cuprates  [招待講演]

  Migaku Oda

  IISC forum on Mott transition and carrier doping 1997年 口頭発表（招待・特別）
• Studies on atomic image and tunneling spectrum in Bi2Sr2CaCu2O8+ by STM/STS  [招待講演]

  Migaku Oda

  9th international symposium on superconductivity (ISS’96) 1996年 口頭発表（招待・特別）
• 高温超伝導体のSTM像と超伝導ギャップの対称性  [招待講演]

  小田 研

  日本物理学会低温分科会シンポジウム 1995年 口頭発表（招待・特別）
• STM/STS Study on Coexistence of Electronic Superstructures in Cuprate Superconductor Bi2Sr2CaCu2O8+x  [招待講演]

  S. Mizuta, T. Kurosawa, N. Momono, H. Yoshida, M. Oda, M. Ido

  5th ISCPMS (International Symposium on Current Progress in Mathematics and Sciences) 口頭発表（招待・特別）

その他活動・業績

• 光渦パルスを用いた超伝導コヒーレントクエンチの実現

  戸田泰則, 山岡利盛, 土屋聡, 山根啓作, 森田隆二, 小田研 応用物理学会春季学術講演会講演予稿集(CD-ROM) 69th 2022年
• 銅酸化物高温超伝導体Bi2201のコヒーレントクエンチ分光

  秋葉俊宏, 土屋聡, 戸田泰則, 黒澤徹, 小田研 応用物理学会春季学術講演会講演予稿集(CD-ROM) 69th 2022年
• ディスオーダーを持つBi系高温超伝導体の光誘起準粒子ダイナミクス

  秋葉俊宏, 土屋聡, 戸田泰則, 黒沢徹, 小田研, MERTELJ T., MIHAILOVIC D. 日本物理学会講演概要集(CD-ROM) 76 (2) 2021年
• スピン1/2カゴメ反強磁性体CaCu₃(OD)₆Cl₂・0.6D₂Oにおけるq=0長距離磁気秩序

  飯田一樹, 吉田紘行, 中尾朗子, JESCHKE Harald O., IQBAL Yasir, 中島健次, 河村聖子, 宗像孝司, 稲村泰弘, 村井直樹, 石角元志, 熊井玲児, 熊井玲児, 岡田武久, 小田研, 加倉井和久, 松田雅昌 日本物理学会講演概要集(CD-ROM) 76 (1) 2021年
• カゴメ反強磁性体Caカペラサイトにおけるギャップレス磁気励起の観測

  井原慶彦, 佐々木孝彦, 野口直彌, 石井裕人, 小田研, 吉田紘行 Selected Topics Research Highlight at HFLSM 2017 5 2018年10月 [査読無し][通常論文]
  
• β“‐(BEDT‐TTF)₄[(H₃O)Ga(C₂O₄)₃]・C₆H₅NO₂のSTM/STS

  市村晃一, 小久保宏樹, 丹田聡, 黒澤徹, 小田研, 本間弘樹, 松永悟明, 森部一斗, 井原慶彦, 河本充司 日本物理学会講演概要集(CD-ROM) 73 (2) ROMBUNNO.11aK302‐7 2018年09月21日 [査読無し][通常論文]
  
• カゴメ格子反強磁性体Li₂Cr₃SbO₈の磁性

  石井裕人, 吉田紘行, 小田研, 木田孝則, 鳴海康雄, 萩原政幸 セラミックス基礎科学討論会講演要旨集 56th 2018年
• S=5/2三角格子ダイマーCs₃Fe₂Cl₉の磁気相図 II

  石井裕人, 松下能孝, 吉田紘行, 小田研, 萩原雅人, 益田隆嗣, 木田孝則, 鳴海康雄, 萩原政幸 日本物理学会講演概要集(CD-ROM) 72 (2) ROMBUNNO.21aPS‐20 -644 2017年09月25日 [査読無し][通常論文]
  
• 擬カゴメ格子反強磁性体CdCu₃(OH)₆Cl₂の1/3磁化プラトー

  吉田紘行, 野口直彌, 石井裕人, 小田研, CHEN J, 山浦一成, 木田孝則, 鳴海康雄, 萩原政幸 日本物理学会講演概要集(CD-ROM) 72 (2) ROMBUNNO.22aE20‐2 -778 2017年09月25日 [査読無し][通常論文]
  
• 光渦パルス励起による超伝導準粒子軌道角運動量ダイナミクス観測

  望月洋人, 戸田泰則, 土屋聡, 山根啓作, 森田隆二, 黒沢徹, 小田研 応用物理学会秋季学術講演会講演予稿集(CD-ROM) 78th ROMBUNNO.6a‐S45‐5 2017年08月25日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体CaCu₃(OH)₆Cl₂・0.6H₂Oの³⁵Cl‐NMRによる研究

  吉田紘行, 井原慶彦, 野口直彌, 石井裕人, 高田篤, 木田孝則, 鳴海康雄, 萩原政幸, 河本充司, 佐々木孝彦, 小田研 日本物理学会講演概要集(CD-ROM) 72 (1) ROMBUNNO.19pC31‐9 -1247 2017年03月21日 [査読無し][通常論文]
   

  CaCu_3_(OH)_6_Cl_2_・0.6H_2_OはS = 1/2カゴメ格子反強磁性体の良いモデル物質である。本講演では、19 Tまでの粉末強磁場NMR、5.5 Tまでの単結晶NMRの結果を報告し、CaCu_3_(OH)_6_Cl_2_・0.6H_2_Oの基底状態について議論する。

• 銅酸化物高温超伝導体の超伝導ギャップ・擬ギャップダイナミクス

  戸田泰則, 黒澤 徹, 小田 研 日本物理学会誌 71 (12) 830 -835 2016年12月 [査読有り][招待有り]
   

  超伝導は物理学における最も魅力的な現象の一つであり，カマリング・オネスによる発見から今日に至るまで多くの研究者を魅了してきた．なかでも液体窒素温度をはるかに上回る転移温度を示す銅酸化物は，いわゆる高温超伝導体のプロトタイプとして数多くの研究がなされ，今も新たな知見や問題提起が次々と報告されている．

  超伝導状態では電子間に有効な引力が作用して電子対（クーパー対）が形成され，複数の電子対が位相をそろえて量子凝縮する．凝縮が起こると，フェルミ面近傍の電子スペクトルには，対演算子の期待値（ギャップ関数）によって特徴づけられるエネルギーギャップが開く．Bardeen–Cooper–Schrieffer (BCS) の理論によって説明される従来型超伝導では，格子振動（フォノン）を介した引力で形成される電子対がフェルミ面上に等方的なs波対称性を持つギャップを形成する．これに対して電子間に強い斥力の働く銅酸化物高温超伝導体のギャップは，有効な引力を獲得するために異方的なギャップ関数を持つと考えられており，フェルミ面上にギャップの節（ノード）を持つd波対称性を示す．また超伝導転移温度(T_c)以上でフェルミ面の一部に擬ギャップと呼ばれるギャップ構造が形成されることが知られており，特に反強磁性絶縁相に近いアンダードープ(UD)試料ではT_cよりはるかに高温から観測される．擬ギャップの存在は銅酸化物高温超伝導体の最大の特徴であり，古くから精力的な研究がなされているが，超伝導の前駆現象から超伝導と共存/ 競合する秩序相など様々な解釈があり，結論を見ていない．また物質や測定手法に応じて多様な性質を示すため，ギャップの起源や形成メカニズムを決定するには，多面的かつ系統的な物性観測が必要とされている．

  このように多彩な顔を持つ擬ギャップおよび超伝導ギャップと両者の関係性について，従来の実空間や運動量空間の観測手法に加え，超短光パルスを使った時間領域からのアプローチが行われるようになってきた．本稿では物性観測に広く使われる時間分解ポンププローブ分光をベースに，この手法が，これまで観測できなかった高温超伝導体のバルク性質を反映した対称性解析，および秩序形成の相関スケール解析へと拡張可能であることを示す．本稿で扱うポンププローブ分光では，ポンプ光を用いてギャップを形成する電子または正孔（キャリア）を瞬時的に破壊し，高エネルギー状態へと励起する．キャリアのエネルギー緩和に伴って生成される非平衡な準粒子やフォノンは（超伝導・擬ギャップに対応する）ギャップ関数の変化を反映し，ポンプ光に対して遅延時間を持つプローブ光の反射率変化として測定される．励起に使用する光子エネルギーはギャップエネルギーよりもはるかに大きいが，結晶内部への侵入長を大きく取れるため，バルク性質を反映する．拡張されたポンププローブ分光は，それぞれ超伝導ギャップおよび擬ギャップに起因する準粒子応答を一意に決定可能であり，超伝導前駆現象を反映する揺らぎ状態を含め，超伝導ギャップと擬ギャップの個性および両者の関係性をダイナミクスの観点から明らかにする．偏光応答に着目した対称性解析では，擬ギャップの形成温度T ^*以下で自発的な回転対称性破れが生じることが示される．他方，秩序形成ダイナミクスからは，擬ギャップが長距離相関のない局在状態を反映することが明らかとなる．

• S=5/2三角格子ダイマーCs₃Fe₂Cl₉の磁気相図

  石井裕人, 松下能孝, 吉田紘行, 小田研, 高田篤, 木田孝則, 鳴海康雄, 萩原政幸 日本物理学会講演概要集(CD-ROM) 71 (2) ROMBUNNO.13pAA‐7 2016年09月23日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体CaCu₃(OH)₆Cl₂・0.6H₂O単結晶の磁性

  吉田紘行, 野口直彌, 石井祐人, 片岡萌子, 小田研, 岡部博孝, 岡部博孝, 飯田一樹, 山下智史, 中澤康浩, 高田篤, 木田孝則, 鳴海康雄, 萩原政幸 日本物理学会講演概要集(CD-ROM) 71 (2) ROMBUNNO.16aAG‐14 -1024 2016年09月23日 [査読無し][通常論文]
   

  我々はS = 1/2カゴメ格子反強磁性体CaCu_3_(OH)_6_Cl_2_・0.6H_2_Oの単結晶育成に成功した。T^*^ = 7 Kに磁気秩序の形成を示唆する磁化、比熱の異常が観測された。また、比熱には温度比例項が存在し、何らかの特異な磁気励起の存在が示唆される。当日は、単結晶を用いた結晶構造解析、磁化、比熱、強磁場磁化測定の結果について報告し、本物質の特異な磁性について議論する予定である。

• S=3/2カゴメ格子反強磁性体Li₂Cr₃SbO₈の1/9磁化プラトー

  石井裕人, 吉田紘行, 小田研, 岡部博孝, 岡部博孝, 飯田一樹, 高田篤, 木田孝則, 鳴海康雄, 萩原政幸 日本物理学会講演概要集(CD-ROM) 71 (2) ROMBUNNO.16aAG‐10 -1020 2016年09月23日 [査読無し][通常論文]
   

  今回我々は、S = 3/2カゴメ格子反強磁性体Li_2_Cr_3_SbO_8_の粉末試料を用いた磁化、比熱、強磁場磁化過程の測定を行った。T^*^ =4 Kにおいて磁気状態の形成を示唆する磁化、比熱の異常が観測され、強磁場磁化測定からはT^*^以下で1/9磁化プラトーが観測された。本公演では、以上の実験結果を詳細に報告するとともに、その磁性について議論する。

• Pb置換を行ったBi₂Sr₂CaCu₂O_8+δにおける光誘起準粒子ダイナミクス

  渡邉健太, 土屋聡, 戸田泰則, 板垣征一朗, 黒澤徹, 小田研 応用物理学会北海道支部/日本光学会北海道支部合同学術講演会講演予稿集 51st-12th 2016年
• S=3/2カゴメ格子反強磁性体Li₂Cr₃SbO₈のμSR

  岡部博孝, 岡部博孝, 竹下聡史, 平石雅俊, 幸田章宏, 幸田章宏, 小嶋健児, 小嶋健児, 門野良典, 門野良典, 石井裕人, 小田研, 吉田紘行 日本物理学会講演概要集(CD-ROM) 71 (2) 2016年
• 9aPS-79 Fe-doped Bi_2Sr_<2-x>La_xCuO_<6+δ>の擬ギャップと超伝導(9aPS 領域8ポスターセッション(遷移金属酸化物・鉄砒素系など),領域8(強相関系))

  清水 茉椰, 鈴木 順也, 桃野 直樹, 雨海 有佑, 高野 英明, 村山 茂幸, 黒澤 徹, 小田 研, 伊土 政幸 日本物理学会講演概要集 69 (2) 421 -421 2014年08月22日
• 9aPS-91 STM/STSから見たBi_2Sr_2CaCu_2O_<8+y>における不純物効果(9aPS 領域8ポスターセッション(遷移金属酸化物・鉄砒素系など),領域8(強相関系))

  原田 諒佑, 鈴木 順也, 曽田 純平, Baar Stefan, 桃野 直樹, 雨海 有佑, 高野 英明, 村山 茂幸, 黒澤 徹, 小田 研, 伊土 政幸 日本物理学会講演概要集 69 (2) 423 -423 2014年08月22日
• STM/STSから見たアンダードープ領域におけるBi2212の電荷秩序と擬ギャップ

  板垣征一朗, 黒澤徹, 米川雄太, 竹山幸作, 桃野直樹, 吉田紘行, 小田研, 伊土政幸 日本物理学会講演概要集 69 (2) 320 -320 2014年08月22日 [査読無し][通常論文]
  
• STM/STSからみたBi2212の超伝導に対するNi不純物効果

  浦田理礼, 柴田悠人, 黒澤徹, 吉田紘行, 桃野直樹, 小田研, 伊土政幸 日本物理学会講演概要集 69 (2) 421 -421 2014年08月22日 [査読無し][通常論文]
  
• STM/STSから見たBi2212の1次元変調構造とギャップサイズの相関

  野並拓矢, 吉田紘行, 岸文香, 黒澤徹, 戸田泰則, 竹山幸作, 小田研, 伊土政幸 日本物理学会講演概要集 69 (2) 421 -421 2014年08月22日 [査読無し][通常論文]
  
• 28aPS-102 STM/STS studies of the Pseudogap and the Superconducting properties of overdoped Bi2212

  Baar Stefan, Shimizu M., Moriya Y., Harada R., Momono N., Takano H., Kurosawa T., Oda M., Ido M. 日本物理学会講演概要集 69 (1) 616 -616 2014年03月05日
• Bi₂Sr₂CaCu₂O_8+δのノード・アンチノード対称性にもとづく光誘起準粒子ダイナミクスの選択的観測

  渡辺健太, 土屋聡, 戸田泰則, 板垣征一朗, 黒澤徹, 小田研 応用物理学会秋季学術講演会講演予稿集(CD-ROM) 75th 2014年
• 26aKQ-8 OD-Bi2212の光誘起超伝導相転移における準粒子ダイナミクス(銅酸化物1,領域8(強相関系分野:高温超伝導,強相関f電子系など))

  川之上 史篤, 戸田 泰則, 板垣 征一朗, 黒澤 徹, 小田 研, 伊土 政幸 日本物理学会講演概要集 68 (2) 500 -500 2013年08月26日
• 26aPS-57 La-Bi2201系銅酸化物における超伝導ギャップの場所依存性およびホール濃度依存性(領域8ポスターセッション(理論,空間非対称,アクチノイドなど),領域8(強相関系分野:高温超伝導,強相関f電子系など))

  阿部 哲, 北村 友, 田島 健士, 清水 茉椰, 桃野 直樹, 雨海 有佑, 村山 茂幸, 高野 英明, 黒澤 徹, 小田 研, 伊土 政幸 日本物理学会講演概要集 68 (2) 514 -514 2013年08月26日
• 26aPS-59 STM/STSから見たBi2212の電荷秩序とエネルギーギャップ(領域8ポスターセッション(理論,空間非対称,アクチノイドなど),領域8(強相関系分野:高温超伝導,強相関f電子系など))

  中川 安徳, 山路 潤, 黒澤 徹, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 68 (2) 514 -514 2013年08月26日
• 26aPS-61 Bi2212系とBi2201系銅酸化物のギャップ構造と超伝導(領域8ポスターセッション(理論,空間非対称,アクチノイドなど),領域8(強相関系分野:高温超伝導,強相関f電子系など))

  田島 健士, 阿部 哲, 北村 友, 原田 諒佑, 桃野 直樹, 雨海 有佑, 村山 茂幸, 高野 英明, 黒澤 徹, 小田 研, 伊土 政幸 日本物理学会講演概要集 68 (2) 515 -515 2013年08月26日
• 26aPS-63 銅酸化物超伝導体Bi_2Sr_<2-x>Ln_xCuO_<6+δ>(Ln=Eu,La)のエネルギーギャップに対するSrサイト置換効果(領域8ポスターセッション(理論,空間非対称,アクチノイドなど),領域8(強相関系分野:高温超伝導,強相関f電子系など))

  北村 友, 阿部 哲, 田島 健士, 守屋 佑基, 桃野 直樹, 雨海 有佑, 村山 茂幸, 高野 英明, 黒澤 徹, 小田 研, 伊土 政幸 日本物理学会講演概要集 68 (2) 515 -515 2013年08月26日
• 26aPS-58 STM/STSから見たEu-Bi2201の電荷秩序とギャップ構造(領域8ポスターセッション(理論,空間非対称,アクチノイドなど),領域8(強相関系分野:高温超伝導,強相関f電子系など))

  吉川 一真, 黒澤 徹, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 68 (2) 514 -514 2013年08月26日
• 29aRG-2 1T-VSe_2におけるカイラルCDWの発見(29aRG 超伝導・密度波,領域6(金属,超低温,超伝導・密度波))

  菅原 悠太, 石岡 準也, 戸田 康則, 小田 研, 黒澤 徹, 松浦 徹, 市村 晃一, 丹田 聡 日本物理学会講演概要集 68 (1) 892 -892 2013年03月26日
• オーバードープ高温超伝導体(Bi2212)の光誘起超伝導相転移における準粒子ダイナミクス

  川之上史篤, 土屋聡, 戸田泰則, 板垣征一朗, 黒澤徹, 小田研, 伊土政幸 応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 49th-10th 2013年
• Reply to "Comment on 'Charge-parity symmetry observed through Friedel oscillations in chiral charge-density waves' "

  J. Ishioka, T. Fujii, K. Katono, K. Ichimura, T. Kurosawa, M. Oda, S. Tanda PHYSICAL REVIEW B 86 (24) 2012年12月 [査読無し][通常論文]
   

  We are responding to the Comment by J. Wezel on our paper. This study was developed from our previous work [Ishioka et al., Phys. Rev. Lett. 105, 176401 (2010)]. In the PRL paper, H-CDW was defined as a new parameter for expressing CDW chirality for the first time. In his Comment, he claims that H-CDW is ill defined. He also claims that the initial phase phi of the CDW wave function is a more appropriate parameter for expressing chiral CDW, despite our early introduction of phi to explain the experimental data described in the PRL paper. However, we conclude that H-CDW can distinguish the CDW chirality by its sign. Moreover, by considering different H-CDW signs, we had succeeded in demonstrating the difference of the spatial distributions of CDWs as shown in Fig. 4 of the PRB paper [Phys. Rev. B 84, 245125 (2011)]. In our Reply, we discuss the validity of H-CDW. We show that his argument regarding the identification of the CDW with the opposite sign of q is wrong, since the logic is inapplicable to a wave function with a nonzero phi. We also discuss the applicability of H-CDW to two- or three-dimensional CDWs in transition metal dichalcogenides. DOI: 10.1103/PhysRevB.86.247102
• 21aGB-10 STM/STSから見たBi系超伝導体の電荷秩序とストライプ(21aGB 高温超伝導2(スペクトロスコピー),領域8(強相関系:高温超伝導強相関f電子系など))

  山路 潤, 八田 曉, 宮崎 弘, 黒澤 徹, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 67 (2) 585 -585 2012年08月24日
• 25pYH-10 UD-Bi2212の光誘起超伝導相転移における準粒子ダイナミクス(25pYH 高温超伝導2(理論・電子構造・スペクトロスコピー),領域8,強相関系:高温超伝導,強相関f電子系など)

  戸田 泰則, Mertelj T., Kusar P., 黒澤 徹, 小田 研, 伊土 政幸, Mihailovic D. 日本物理学会講演概要集 67 (1) 648 -648 2012年03月05日
• 24pGM-10 STM/STSから見たBi系超伝導体における電荷秩序と実効的超伝導ギャップ(24pGM 銅酸化物(超伝導・電子状態),領域8(強相関系:高温超伝導,強相関f電子系など))

  宮崎 弘, 山路 潤, 山上 佳丈, 黒澤 徹, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 66 (2) 661 -661 2011年08月24日
• 22aPS-36 STM/STSから見たBi-La2201の電荷秩序とギャップ構造のホール濃度依存性(22aPS 領域8ポスターセッション(低温1(遷移金属酸化物・超伝導など)),領域8(強相関系:高温超伝導,強相関f電子系など))

  八田 曉, 竹内 卓総, 山路 潤, 黒澤 徹, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 66 (2) 517 -517 2011年08月24日
• 23pGM-5 FeTeの電子状態 : STM/STS(23pGM 鉄砒素系(11系),領域8(強相関系:高温超伝導,強相関f電子系など))

  河島 佑樹, 黒澤 徹, 市村 晃一, 小田 研, 山谷 和彦, 丹田 聡 日本物理学会講演概要集 66 (2) 625 -625 2011年08月24日 [査読無し][通常論文]
  
• 電荷密度波における電荷,パリティ対称性:1T‐TiSe₂におけるフリーデル振動の観測

  石岡準也, 藤井敏之, 市村晃一, 小田研, 丹田聡 日本物理学会講演概要集 66 (2) 801 -801 2011年08月24日 [査読無し][通常論文]
  
• FeTeの電子状態:STM/STS

  河島佑樹, 黒澤徹, 市村晃一, 小田研, 山谷和彦, 丹田聡 日本物理学会講演概要集 66 (2) 625 2011年08月24日 [査読無し][通常論文]
  
• 27pGW-6 FeTeの電子状態 : STM/STS(27pGW 鉄砒素系(11系),領域8(強相関係:高温超伝導,強相関f電子系など))

  河島 佑樹, 黒澤 徹, 市村 晃一, 小田 研, 山谷 和彦, 丹田 聡 日本物理学会講演概要集 66 (1) 641 -641 2011年03月03日 [査読無し][通常論文]
  
• 23pXP-4 STM/STSから見たBi2212のCu-O面における電荷秩序と実効的超伝導ギャップ(23pXP 高温超伝導1(トンネル分光・輸送特性など),領域8(強相関系:高温超伝導,強相関f電子系など))

  山上 佳丈, 宮崎 弘, 黒澤 徹, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 65 (2) 508 -508 2010年08月18日
• 23pXP-3 STM/STSから見たBi-La2201の2次元電荷秩序とフェルミ面でのギャップ構造(23pXP 高温超伝導1(トンネル分光・輸送特性など),領域8(強相関系:高温超伝導,強相関f電子系など))

  竹内 卓総, 八田 曉, 黒澤 徹, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 65 (2) 508 -508 2010年08月18日
• 23aPS-15 STM/STSから見たアンダードープBi2212の超伝導ギャップ、擬ギャップと電荷秩序(23aPS 領域8ポスターセッション(低温I(鉄系超伝導,銅酸化物など)),領域8(強相関系:高温超伝導,強相関f電子系など))

  北島 裕介, 黒澤 徹, 横内 嵩之, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 65 (2) 463 -463 2010年08月18日
• 20aHX-2 電荷密度波カイラリティの発見 : 1T-TiSe_2におけるSTM・光学測定による面内異方CDWの観測(20aHX 超伝導・電荷密度波,領域6(金属,超低温,超伝導・密度波))

  石岡 準也, 島竹 克大, 黒澤 徹, 市村 晃一, 戸田 泰則, 小田 研, 丹田 聡 日本物理学会講演概要集 65 (1) 812 -812 2010年03月01日 [査読無し][通常論文]
  
• 27pPSB-16 CaCu_3T_i4O_<12>単結晶の誘電挙動(領域10ポスターセッション(誘電体),領域10,誘電体,格子欠陥,X線・粒子線,フォノン物性)

  上村 雄基, 武貞 正樹, 伊土 政幸, 小田 研, 小野寺 彰 日本物理学会講演概要集 64 (2) 887 -887 2009年08月18日
• 26pRK-5 STM/STSから見たBi系銅酸化物高温超電導体のノーダル超伝導(高温超伝導(光電子分光,トンネル分光,光学応答など),領域8,強相関系:高温超伝導,強相関f電子系など)

  萩原 聖, 黒澤 徹, 竹山 幸作, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 64 (2) 515 -515 2009年08月18日
• 25aRH-7 鉄系超伝導体のSTM/STS(鉄系超伝導体I(超伝導状態・対称性など),領域8,強相関系:高温超伝導,強相関f電子系など)

  河島 佑樹, 市村 晃一, 黒澤 徹, 小田 研, 丹田 聡, 高橋 博樹, 岡田 宏成, 神原 陽一, 細野 秀雄 日本物理学会講演概要集 64 (2) 406 -406 2009年08月18日 [査読無し][通常論文]
  
• 30aRF-11 単結晶CaCu_3Ti_4O_<12>の作製と誘電測定(30aRF 誘電体(酸化物),領域10(誘電体,格子欠陥,X線・粒子線,フォノン物性))

  川谷 恵一, 藤本 圭佑, 伊土 政幸, 小田 研, 小野寺 彰 日本物理学会講演概要集 64 (1) 977 -977 2009年03月03日
• 23pQE-6 STM/STSから見たBi系銅酸化物高温超伝導体のチェッカーボード変調とギャップ構造(23pQE 高温超伝導(NMR・STM・その他),領域8(強相関系:高温超伝導,強相関f電子系など))

  井上 諒, 萩原 将也, 藤本 圭佑, 黒澤 徹, 萩原 望, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 63 (2) 579 -579 2008年08月25日
• 20pYD-3 Spatially non-uniform pseudogap structure of high T_c superconductor observed by STM/STS

  伊土 政幸, Momono N., Oda M. 日本物理学会講演概要集 63 (2) 626 -626 2008年08月25日
• 20pPSB-9 電子ラマン散乱からみたBi2212における不純物効果(20pPSB 領域8ポスターセッション(低温:Cu酸化物,Ru酸化物,Co酸化物),領域8(強相関系:高温超伝導,強相関f電子系など))

  内藤 将士, 古谷 俊輔, 黒澤 徹, 雨海 有佑, 桃野 直樹, 高野 英明, 村山 茂幸, 酒井 彰, 小田 研, 伊土 正幸 日本物理学会講演概要集 63 (2) 471 -471 2008年08月25日
• 20pQE-4 磁場中比熱から見たLa214系の超伝導に対する不純物効果II(20pQE 高温超伝導(置換効果・不純物効果),領域8(強相関系:高温超伝導,強相関f電子系など))

  黒澤 徹, 川崎 郁斗, 桃野 直樹, 網塚 浩, 小田 研, 伊土 政幸 日本物理学会講演概要集 63 (2) 453 -453 2008年08月25日
• Incoherent CDWにおけるFriedel振動のSTM観測

  石岡準也, 黒澤徹, LIU Y. H, 豊嶋剛司, 市村晃一, 小田研, 丹田聡 日本物理学会講演概要集 63 (2) 688 2008年08月25日 [査読無し][通常論文]
  
• 20aYE-2 Incoherent CDWにおけるFriedel振動のSTM観測(20aYE 電荷密度波・超伝導,領域6(金属,超低温,超伝導・密度波))

  石岡 準也, 黒澤 徹, 劉 英豪, 豊嶋 剛司, 市村 晃一, 小田 研, 丹田 聡 日本物理学会講演概要集 63 (2) 688 -688 2008年08月25日 [査読無し][通常論文]
  
• 24pWQ-1 磁場中比熱から見たLa214系の超伝導に対する不純物効果(24pWQ 高温超伝導(不純物置換,同位体効果),領域8(強相関係:高温超伝導,強相関f電子系など))

  黒澤 徹, 来栖 潔, 桃野 直樹, 小田 研, 伊土 政幸, 生沼 慎也, 網塚 浩 日本物理学会講演概要集 63 (1) 605 -605 2008年02月29日
• 24aRH-2 STM/STSから見たLa-Bi2201及びBi2212のチェッカーボード変調と大きな擬ギャップ(24aRH 高温超伝導(STM,トンネル効果),領域8(強相関係:高温超伝導,強相関f電子系など))

  萩原 将也, 米山 貴之, 高野 由衣, 黒澤 徹, 井上 諒, 劉 英豪, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 63 (1) 557 -557 2008年02月29日
• 26aRH-2 電子ラマン散乱から見たBi2212における超伝導ギャップと擬ギャップ(26aRH 高温超伝導(擬ギャップと超伝導ギャップ),領域8(強相関係:高温超伝導,強相関f電子系など))

  桃野 直樹, 山口 蓉子, 越前 尚紀, 黒澤 徹, 小田 研, 伊土 政幸, 高野 英明, 村山 茂幸, 酒井 彰 日本物理学会講演概要集 63 (1) 629 -629 2008年02月29日
• 26aRH-3 ポンプ・プロープ分光でみたBi2212の超伝導状態と擬ギャップ状態における準粒子緩和(26aRH 高温超伝導(擬ギャップと超伝導ギャップ),領域8(強相関係:高温超伝導,強相関f電子系など))

  劉 英豪, 戸田 泰則, 島竹 克大, 桃野 直樹, 小田 研, 伊土 政幸, 黒澤 徹 日本物理学会講演概要集 63 (1) 630 -630 2008年02月29日
• 21aPS-29 Bi2212におけるチェッカーボード変調と超伝導ギャップ構造(領域8ポスターセッション(低温),領域8,強相関系:高温超伝導,強相関f電子系など)

  高野 由衣, 黒澤 徹, 来栖 潔, 米山 貴之, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 62 (2) 525 -525 2007年08月21日
• 24aWG-10 STM/STSから見たLa_<2-x>Sr_xCuO_4およびLa_<2-x-y>Nd_ySr_xCuO_4の電子構造(高温超伝導(ARPES(II),ラマン散乱,トンネル分光),領域8,強相関係:高温超伝導,強相関f電子系など)

  桃野 直樹, 来栖 潔, 黒澤 徹, 米山 貴之, 高野 由衣, 竹山 幸作, 小田 研, 伊土 政幸 日本物理学会講演概要集 62 (2) 650 -650 2007年08月21日
• 22pWJ-8 銅酸化物高温超伝導体における不均一超伝導状態 : 擬ギャップ、電荷秩序との関連性(領域6,領域8合同シンポジウム主題:不均一超流動・超伝導の物理,領域6,金属,超低温,超伝導・密度波)

  小田 研, 劉 英豪, 桃野 直樹, 伊土 政幸 日本物理学会講演概要集 62 (2) 820 -820 2007年08月21日
• 18pWP-7 STM/STSから見たLa_<2-x>Sr_xCuO_4の超伝導ギャップとフェルミアーク(18pWP 高温超伝導(STM,ラマン散乱,光学応答),領域8(強相関系:高温超伝導,強相関f電子系など))

  来栖 潔, 黒澤 徹, 米山 貴之, 高野 由衣, 竹山 幸作, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 62 (1) 509 -509 2007年02月28日
• 18pWP-2 Bi2212の擬ギャップ状態におけるチェッカーボード型電荷秩序のSTM観察(18pWP 高温超伝導(STM,ラマン散乱,光学応答),領域8(強相関系:高温超伝導,強相関f電子系など))

  竹山 幸作, 劉 英豪, 石倉 光男, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 62 (1) 507 -507 2007年02月28日
• 23aZR-7 電子比熱から見たLa_<2-x>Sr_xCu_<1-y>Ni_yO_4におけるノーダル超伝導(23aZR 高温超伝導(輸送現象・光学応答I),領域8(強相関系:高温超伝導,強相関f電子系など))

  黒澤 徹, 高野 由衣, 来栖 潔, 米山 貴之, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 61 (2) 391 -391 2006年08月18日
• 25pZQ-2 STM/STSから見たBi2212の4a×4a電荷秩序と擬ギャップ(25pZQ 高温超伝導(トンネル分光),領域8(強相関係:高温超伝導,強相関f電子系など))

  石倉 光男, 竹山 幸作, 劉 英豪, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 61 (2) 507 -507 2006年08月18日
• 27pTD-8 STM/STSから見たBi2212の超伝導状態における4a×4a電荷秩序(27pTD 高温超伝導(トンネル分光),領域8(強相関系:高温超伝導,強相関f電子系など))

  橋本 暁仁, 杉田 想土, 市川 祐也, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 61 (1) 557 -557 2006年03月04日
• 27pTD-8 STM/STSから見たBi2212の擬ギャップ状態(T>>Tc)における4ax4a電荷秩序(27pTD 高温超伝導(トンネル分光),領域8(強相関系:高温超伝導,強相関f電子系など))

  劉 英豪, 竹山 幸作, 石倉 光男, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 61 (1) 558 -558 2006年03月04日
• 27pTD-7 STM/STSから見たLa_<2-x>Sr_xCuO_4の局所電子状態(27pTD 高温超伝導(トンネル分光),領域8(強相関系:高温超伝導,強相関f電子系など))

  桃野 直樹, 後藤 高明, 遠洞 竜生, 橋本 暁仁, 小田 研, 伊土 政幸, 酒井 彰 日本物理学会講演概要集 61 (1) 557 -557 2006年03月04日
• Doping dependence of the vortex glass and sublimation transitions in the high-T-c superconductor La2-xSrxCuO4 as determined from macroscopic measurements

  R Gilardi, S Streule, N Momono, M Oda, J Mesot EUROPEAN PHYSICAL JOURNAL B 47 (2) 231 -237 2005年09月 [査読無し][通常論文]
   

  Magnetization and ac-susceptibility measurements are used to characterize the mixed phase of the high-temperature cuprate superconductor La2-xSrxCuO4 over a large range of doping (0.075 <= x <= 0.20). The first order vortex lattice phase transition line H-FOT(T), the upper critical field H-c2(T) and the second peak H-sp(T) have been investigated up to high magnetic fields (8 Tesla applied perpendicular to the CuO2 planes). Our results reveal a strong doping dependence of the magnetic phase diagram, which can mainly be explained by the increasing anisotropy with underdoping. Within our interpretation, the. rst order vortex lattice phase transition is due to the sublimation ( rather than melting) of the vortex lattice into a gas of pancake vortices, whereas the second peak is related to the transition to a more disordered vortex glass state.
• 21pYG-2 STM/STSから見たBi2212の電荷秩序に対する不純物効果(高温超伝導(トンネル分光,面間輸送),領域8(強相関系 : 高温超伝導,強相関f電子系など))

  杉田 想土, 市川 祐也, 橋本 暁仁, 石倉 光男, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 60 (2) 491 -491 2005年08月19日
• 20pXD-2 電子比熱から見たLa214系の超伝導ギャップに対するNi不純物効果(高温超伝導(置換効果 結晶化学),領域8(強相関系 : 高温超伝導,強相関f電子系など))

  遠洞 竜生, 石倉 光男, 松崎 俊明, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 60 (2) 450 -450 2005年08月19日
• 24pWA-7 La_<2-x>Sr_xCuO_4における低温STM/STS II(高温超伝導(トンネル分光・輸送特性),領域8(強相関系:高温超伝導,強相関f電子系など))

  後藤 高明, 中村 さなえ, 橋本 暁仁, 遠洞 竜生, 石倉 光男, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 60 (1) 499 -499 2005年03月04日
• 24pWA-1 STM/STSから見たアンダードープBi2212の電子状態の場所依存性(高温超伝導(トンネル分光・輸送特性),領域8(強相関系:高温超伝導,強相関f電子系など))

  橋本 暁仁, 小畑 康生, 杉田 想土, 市川 裕也, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 60 (1) 498 -498 2005年03月04日
• STM/STS study on local electronic states of underdoped Bi 2Sr2CaCu2O8+δ

  N. Momono, A. Hashimoto, Y. Kobatake, S. Nakamura, M. Oda, M. Ido International Journal of Modern Physics B 19 (1-3) 231 -234 2005年01月03日 [査読無し][通常論文]
   

  Spatial variation of low temperature tunneling spectrum on atomic scale was examined on the slightly underdoped Bi2212 sample (Tc ∼74K, p ∼0.12) by using a STM/STS technique. We observed a V-shaped gap with sharp coherence peaks, which is expected for d-wave superconductors, over the distance of ~∼18 nm and no other kind of gap. The spatial variation of gap size Δ0 is small, ranging from 41 to 53 meV. These results indicate that the superconductivity takes place rather homogeneously in the slightly underdoped sample. World Scientific Publishing Company.
• 13aRA-7 La_<2-x>Sr_xCuO_4 における低温 STM/STS(高温超伝導 : トンネル分光, 領域 8)

  中村 さなえ, 後藤 高明, 遠藤 竜生, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 59 (2) 447 -447 2004年08月25日
• 13aPS-9 La_<2-x>Sr_xCuO_4 のアンドレーエフ束縛状態(低温 : 超伝導・金属絶縁体転移, 領域 8)

  竹山 幸作, 小田 研, 桃野 直樹, 伊土 政幸 日本物理学会講演概要集 59 (2) 462 -462 2004年08月25日
• 13aRA-11 STM/STS からみた Bi2212 のアンダードープにおける電子状態の場所依存性(高温超伝導 : トンネル分光, 領域 8)

  小畑 康生, 橋本 暁仁, 市川 裕也, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 59 (2) 448 -448 2004年08月25日
• Field-induced hexagonal to square transition of the vortex lattice in overdoped La1.8Sr0.2CuO4

  R Gilardi, J Mesot, AJ Drew, U Divakar, SL Lee, NH Andersen, J Kohlbrecher, N Momono, M Oda PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 408 (491) 491 -492 2004年08月 [査読無し][通常論文]
   

  We report on a small angle neutron scattering study of the vortex lattice in overdoped La2-xSrxCuO4 (x = 0.2) up to high magnetic fields (9.5 T) applied perpendicular to the CuO2 planes. At low magnetic fields we observe a crossover from hexagonal to square coordination of the vortex lattice. This field-induced transition confirms the results obtained in slightly overcloped La2-xSrxCuO4 (x = 0.17). (C) 2004 Elsevier B.V. All rights reserved.
• Spin dynamics in the mixed phase of La2-xSrxCuO4 (x=0.10, x=0.17)

  R Gilardi, S Streule, A Hiess, HM Ronnow, M Oda, N Momono, M Ido, J Mesot PHYSICA B-CONDENSED MATTER 350 (1-3) 72 -75 2004年07月 [査読無し][通常論文]
   

  We present an inelastic neutron scattering study of the spin dynamics in the mixed phase of the high-T-c superconductor La2-xSrxCuO4, In the overdoped regime (x = 0. 17, T-c = 37 K) the application of a magnetic field induces a spectral weight redistribution centered around the zero-field spin gap (Delta(SG) approximate to 5 6.5 meV). Moreover the opening of the spin gap seems to track the irreversibility temperature (related to the melting of the vortex lattice) rather than T-c, indicating an unusual interplay between the mesoscopic and microscopic properties in La2-xSrxCuO4. In the underdoped regime (x = 0. 10, T-c = 29 K) our zero-field data indicate a strong decrease (or even vanishing) of the spin gap in the superconducting state and no dependence upon the application of a magnetic field. (C) 2004 Elsevier B.V. All rights reserved.
• 三浦登, 毛利信男, 重川秀実, 『極限実験技術』, 朝倉書店, 東京,2003, viii+250p., 21.5×15cm, 本体5,200円, (朝倉物性物理シリーズ4), [大学院向・専門書]

  小田 研 日本物理學會誌 59 (4) 243 -243 2004年04月05日
• 28pXE-12 STM/STSからみたBi2212の電子状態の場所依存性(高温超伝導(光電子およびトンネル分光))(領域8)

  桃野 直樹, 橋本 暁仁, 小畑 康生, 中村 さなえ, 小田 研, 伊土 政幸 日本物理学会講演概要集 59 (1) 596 -596 2004年03月03日
• Tunneling spectra near Tc in overdoped Bi2Sr2CaCu2O8+d

  Springer, NATO Science Series II, Mathematics, Physics and Chemistry 183 (31) 2004年 [査読無し][通常論文]
  
• Electronic states near Fermi level in superconductors La2-xSrxCuO4 by means of x-ray absorption spectra near Cu-K and La-L edges

  M Hidaka, N Tokiwa, M Oda, JY Choi, JM Lee PHASE TRANSITIONS 76 (11) 905 -921 2003年11月 [査読無し][通常論文]
   

  The electronic states of La2-xSrxCuO4 with 0.00 less than or equal to x less than or equal to 0.20 are studied by means of X-ray absorption spectroscopy (XANES, EXAFS) near the K-edge of Cu2+ ion and the L-edges of La3+ ion. It is found that characteristic white lines occurring near L-II and L-III edges of La3+ ion show a slight energy shift depending on substituted Sr2+ ions, x and temperature. The white lines suggest that unoccupied high-density 5dpi and 5ddelta bands of La3+ ion just above a Fermi level transform to a hybridized single band of 5dpidelta at 78 K in the superconductors with x = 0.10, 0.16 and 0.20. On the other hand, the XANES spectra near the Cu-K edge including a pre-edge region do not depend on x and temperature in the region of 0.00 less than or equal to x less than or equal to 0.20. It is considered that there is no reconstruction of electronic states at the Fermi level in a Mott-Hubbard band gap between an O 2p valence band and a Cu 3d conduction band. The electronic states at the Fermi level are probably consisted of the unoccupied 5dpidelta band and an empty charge-transfer 3d(9)L band at low temperature, bands of which occur in a band gap between a filled 0 2p valence band and an unoccupied 0 2p conduction band. The insulator-superconductor-metal transitions in La2-xSrxCuO4 are related to the 5dpidelta and 3d9L bands and holes, which site at a top region of the 0 2p valence band near the Fermi level produced by a substitution of La3+ with Sr2+ ions.
• 23aTR-7 Bi2212 の T_c 付近におけるトンネルスペクトル II

  小田 研, 田中 庸介, 桃野 直樹, 伊土 政幸 日本物理学会講演概要集 58 (2) 560 -560 2003年08月15日
• 20aTN-3 中性子散乱からみた La214 系の磁束線格子

  桃野 直樹, 橋本 暁仁, 小田 研, 伊土 政幸, Gilardi R., Streule S., Mesot J., Drew A. J., Divakar U., Lee S. L., Brouwn S. P., Forgan E. M., Andersen N. H., Cubitt R., Dewhurst C. D. 日本物理学会講演概要集 58 (2) 432 -432 2003年08月15日
• 22aPS-15 中性子小角散乱実験による La214 系の磁束線格子の観測

  橋本 暁仁, 桃野 直樹, 小田 研, 伊土 政幸, Gilardi R., Streule S., Mesot J., Drew A. J., Divakar U., Lee S. L., Brouwn S. P., Forgan E. M., Andersen N. H., Cubitt R., Dewhurst C. D. 日本物理学会講演概要集 58 (2) 515 -515 2003年08月15日
• A small angle neutron scattering study of the vortex matter in La2-xSrxCuO4 (x=0.17)

  R Gilardi, S Streule, J Mesot, AJ Drew, U Divakar, SL Lee, SP Brown, EM Forgan, N Momono, M Oda INTERNATIONAL JOURNAL OF MODERN PHYSICS B 17 (18-20) 3411 -3414 2003年08月 [査読無し][通常論文]
   

  The magnetic phase diagram of slightly overdoped La2-xSrxCuO4 (x = 0.17) is characterised by a field-induced hexagonal to square transition of the vortex lattice at low fields (similar to0.4 Tesla) [R. Gilardi et al., Phys. Rev. Lett. 88, 217003 (2002)]. Here we report on a small angle neutron scattering study of the vortex lattice at higher fields, that reveals no further change of the coordination of the square vortex lattice up to 10.5 Tesla applied perpendicular to the CuO2 planes. Moreover, it is found that the diffraction signal disappears at temperatures well below T-c, due to the melting of the vortex lattice.
• 29aWA-10 中性子散乱からみた La214 系の超伝導状態におけるスピンギャップと磁束線格子

  桃野 直樹, 三宅 啓介, 橋本 暁仁, 小田 研, 伊土 政幸, Gilardi R., Streule S., Mesot J., Drew A. J., Divakar U., Lee S. L., Brouwn S. P., Forgan E. M., Andersen N. H., Cubitt R., Dewhurst C. D. 日本物理学会講演概要集 58 (1) 528 -528 2003年03月06日
• Energy gap evolution over wide temperature and doping ranges in Bi2Sr2CaCu2O8+d

  Mod. Phys. Lett. B 17 (401) 2003年 [査読無し][通常論文]
  
• 8pXE-5 銅酸化物高温超伝導体の凝集エネルギーと擬ギャップ(高温超伝導(擬ギャップ,ストライプ),領域8)

  松崎 俊明, 吉澤 季晃, 勢旗 弘子, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 57 (2) 529 -529 2002年08月13日
• 6pPSA-35 La2-xSrxCuO4の凝集エネルギーに対する不純物効果(高温超伝導,領域8)

  吉澤 季晃, 永田 敏夫, 松崎 俊明, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 57 (2) 483 -483 2002年08月13日
• 24aYK-2 Bi2212のT_c近傍におけるエネルギー・ギャップの発展(24aYK 高温超伝導(トンネル・STMその他),領域8(強相関系分野-高温超伝導,強相関f電子系など))

  中野 博之, 今村 英也, Dipasupil R., 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 57 (1) 470 -470 2002年03月01日
• 24aYK-12 La214系における擬ギャップと凝集エネルギー(24aYK 高温超伝導(トンネル・STMその他),領域8(強相関系分野-高温超伝導,強相関f電子系など))

  松崎 俊明, 桃野 直樹, 勢籏 弘子, 永田 敏夫, 小田 研, 伊土 政幸 日本物理学会講演概要集 57 (1) 473 -473 2002年03月01日
• Study on Electronic Specific Heat of La2-xSrxCuO4: Pseudogap and Superconductivity

  Kluwer Academic Publishers 67:167-176 2002年 [査読無し][通常論文]
  
• Correlation between Superconducting Gap and Pseudogap in High-Tc Cuprates

  Kluwer Academic Publishers 67:177-188 2002年 [査読無し][通常論文]
  
• Study on Electronic Specific Heat of La2-xSrxCuO4: Pseudogap and Superconductivity

  Kluwer Academic Publishers 67:167-176 2002年 [査読無し][通常論文]
  
• Correlation between Superconducting Gap and Pseudogap in High-Tc Cuprates

  Kluwer Academic Publishers 67:177-188 2002年 [査読無し][通常論文]
  
• Pseudogap and superconductivity in La2-xSrxCuO4

  T Nagata, N Momono, S Takahashi, M Oda, M Ido PHYSICA C 364 430 -433 2001年11月 [査読無し][通常論文]
   

  We measured the electronic specific heat C-el on La2-xSrxCuO4. The coefficient of the T-linear term of C-el, gamma exhibits a small. broad peak at temperature T* (> T-c) and gradually decreases at T < T*. Temperature T* coincides with the mean-field temperature T-co equivalent to 2 Delta (0)/4.3k(B), and is drastically reduced by Ni-doping in almost the same manner as T-c These results indicate that a pseudogap starts to develop at T approximate to T-co in La214 as well as Bi2212. No pseudogap behavior was observed in x = 0.22 samples. where T-co(T*) approximate to T-c. (C) 2001 Elsevier Science B.V. All rights reserved.
• Pseudogap in the tunneling spectra of slightly overdoped Bi2212

  RM Dipasupil, M Oda, T Nanjo, S Manda, M Momono, M Ido PHYSICA C 364 604 -607 2001年11月 [査読無し][通常論文]
   

  In slightly overdoped Bi2212 with T-c = 82 K, the tunneling spectrum is examined as a function of T by the break junction technique using STM. On the basis of the tunneling data, it is demonstrated that a reduction of spectral weight in almost the same energy range as the low-temperature (T much less than T-c) gap amplitude Delta (0), the so-called "small pseudogap (SPG)", develops progressively below T* similar to 125 K, which is comparable to a mean-field characteristic temperature T-co for d-wave superconductors. We also report that the SPG smoothly develops into the superconducting-state gap at T-c. (C) 2001 Elsevier Science B.V. All rights reserved.
• Observation of the Andreev reflection in the c-axis transport of Bi2Sr2CaCu2O8+x single crystals near T-c and the search for the preformed-pair state

  HS Chang, HJ Lee, M Oda PHYSICAL REVIEW B 64 (13) 2001年10月 [査読無し][通常論文]
   

  We observed an enhancement of the c-axis differential conductance around the zero bias. in Au/Bi2Sr2CaCu2O8+x (Bi2212) junctions near the superconducting transition temperature T-c. We attribute the conductance enhancement to the Andreev reflection between the surface Cu-O bilayer with suppressed superconductivity and the neighboring superconducting inner bilayer. The continuous evolution from depression to an enhancement of the zero-bias differential conductance, as the temperature approaches T-c from below, points to weakening of the barrier strength of the nonsuperconducting layer between adjacent Cu-O bilayers. We observed that the conductance enhancement persisted up to a few degrees above T-c in junctions prepared on slightly overdoped Bi2212 crystals. However, no conductance enhancement was observed above T-c in under-doped crystals, although a recently proposed theoretical consideration suggests an even wider temperature range of enhanced zero-bias conductance. This seems to provide a negative perspective to the existence of the phase-incoherent preformed pairs in the pseudogap state.
• 29pYL-8 電子比熱からみたLa214系の擬ギャップと超伝導

  桃野 直樹, 勢籏 弘子, 高橋 智, 永田 敏夫, 松崎 俊明, 小田 研, 伊土 政幸 日本物理学会講演概要集 56 (1) 552 -552 2001年03月09日
• トンネル分光で見たBi2212のエネルギー・ギャップ

  Dipasupil R. M., 南條 拓真, 萬田 周治, 桃野 直樹, 永田 敏夫, 松崎 俊明, Oda M., 伊土 政幸 日本物理学会講演概要集 56 (1) 553 -553 2001年03月09日
• Superconducting gap and pseudogap behavior in high-Tc cuprates

  T. Matsuzaki, M. Ido, N. Momono, R. M. Dipasupil, T. Nagata, A. Sakai, M. Oda Journal of Physics and Chemistry of Solids 62 (1-2) 29 -33 2001年 [査読無し][通常論文]
   

  We report the low-temperature energy gap 2Δ0 of Bi2Sr2CaCu2O8+δ (Bi2212) and La2-xSrxCuO4 (La214) studied over a wide range of doping levels p, by using STS, break junction tunneling and Raman scattering spectroscopy. We also report the electronic specific heat (Cel) measured in both the superconducting and normal states of La214. First, it is pointed out that the gap magnitude (2Δ0) at T≪Tc is closely related to the crossover temperature (T*) of a small pseudogap in Bi2212, T* to approximately 2Δ0/4 to approximately 5 kB(≡Tco), and the resistivity ρ and magnetic susceptibility χ tend to be slightly suppressed below T*(approximately Tco). A similar suppression appears in both ρ and χ of La214 at T< Tco. The experimental results of Cel indicate that pseudogap behavior appears in La214 below approximately Tco. It is also pointed out that the gap magnitude 2Δ0 is in almost linear proportion to kBTmax, where Tmax(≫T*) is the temperature exhibiting a broad peak in the χ-T curve. Finally, we report that there exists a novel relation between Tc and Δ0, Tc∝pΔ0, in both Bi2212 and La214 systems except in highly-doped samples, where Tc∝2Δ0.
• Novel relation between T-c and low-T energy gap 2 Delta(o) in Bi2212 and La214: an STS study

  M Oda, T Matsuzaki, N Momono, M Ido PHYSICA C 341 (Pt.2) 847 -850 2000年11月 [査読無し][通常論文]
   

  On the basis of electronic specific heat, magnetic susceptibility and STS data in La214, we report that a pseudogap of almost the same scale as the low-T (T<<T-c) gap Delta (o) will develop below T*similar toT(co)=2 Delta (o)/4.3k(B) in La214 as in Bi2212. We also report that over a wide hole doping p range in both systems, T-c almost scales with p Delta (o), and suggest that similar top Delta (o) will function as an effective energy gap in determining T-c.
• What is the energy scale in determining the T-c of cuprate superconductivity?

  M Oda, N Momono, M Ido SUPERCONDUCTOR SCIENCE & TECHNOLOGY 13 (11) R139 -R146 2000年11月 [査読有り][招待有り]
   

  For the understanding of the mechanism of a superconducting transition, it is of great interest to clarify what the energy scale in determining the critical temperature T-c is. According to the BCS mean-field theory, the energy gap at T much less than T-c, 2 Delta (o), is proportional to T-c; 2 Delta (o) = 4.3k(B)T(c) for d-wave superconductors. In the case of high-T-c cuprates, however, 2 Delta (o) increases monotonically with the lowering of the hole-doping level p even in the underdoped region, where T-c is largely suppressed, and does not scale with T-c, except in a highly overdoped region. Interestingly, in a wide p range spreading over the under- and overdoped regions, 2 Delta (o) is almost proportional to crossover temperature T*, around which a spin gap and/or a (small) pseudogap of almost the same energy scale as 2 Delta (o) start to develop progressively; 2 Delta (o)/k(B)T* is nearly independent of p and comparable to the BCS value in the entire p range examined. On the other hand, 2 Delta (o)/k(B)T(c) is inversely proportional to p, 2 Delta (o)/k(B)T(c) similar to 1/p, except in the highly overdoped region, where T-c is very close to the BCS expectation. This indicates that the energy scale in determining T-c is of order p Delta (o) in high-T-c cuprates. In this article, we will discuss some scenarios for the transition from pseudogap to superconducting states, where the energy scale in determining T-c is expected to be of order p Delta (o).
• 25aSG-6 STM/STSとラマン分光から見たBi2212のエネルギー・ギャップ

  萬田 周治, Dipasupil R. M., 南條 拓真, 桃野 直樹, 小田 研, 伊上 政幸, 酒井 彰 日本物理学会講演概要集 55 (2) 546 -546 2000年09月10日
• 25aSG-7 電子比熱から見たLa214の擬ギャップに対する不純物効果

  高橋 智, 松崎 俊明, 永田 敏夫, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 55 (2) 546 -546 2000年09月10日
• 25aSG-3 トンネル分光で見たBi2212擬ギャップ

  南條 拓真, Dipasupil R. M., 萬田 周冶, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 55 (2) 545 -545 2000年09月10日
• 24aZJ-12 電子比熱から見たLa_<2-x>Sr_xCu_<1-y>NiO_4の擬ギャップ

  永田 敏夫, 桃野 直樹, 松崎 俊明, 梅山 貴博, デイパスピル レイニア, 小田 研, 伊土 政幸 日本物理学会講演概要集 55 (1) 529 -529 2000年03月10日
• 24aZJ-13 電子比熱からみた高温超伝導体における超伝導異常のホール濃度依存性

  桃野 直樹, 松崎 俊明, 梅山 貴博, 永田 敏夫, ディパスピル レイニア, 小田 研, 伊上 政幸 日本物理学会講演概要集 55 (1) 530 -530 2000年03月10日
• Pseudogap in Electromic Raman Speetra of Bi₂ Sr₂ CaCu₂ O_{8+δ}

  Physica C 341-348 909 2000年 [査読無し][通常論文]
  
• Correlation between superconducting gap and pseudogap in high-T-c cuprates

  M Ido, N Momono, M Oda JOURNAL OF LOW TEMPERATURE PHYSICS 117 (3-4) 329 -339 1999年11月 [査読無し][通常論文]
   

  We studied the low-temperature energy gap 2 Delta(o) on Bi2Sr2CaCu2O8-delta (Bi2212) and La2-xSrxCuO4 (La214) systematically over a wide range of doping level p using STS, break junction tunneling spectroscopy, Raman scattering and low-T electronic specific heat data. We have also studied the electronic specific heat of La214 in the normal state at T > T-c, and confirmed that pseudogap behavior appears at around T*, below which the in-plane resistivity rho and magnetic susceptibility chi tend to be slightly suppressed. Similar suppression appears in rho and chi of Bi2212 below the onset temperature of pseudogap T*. It is pointed out in the present study that 2 Delta(o) is closely related to T* in both Bi2212 and La214 systems; T* similar to 2 Delta(o)/4.3k(B). It is also pointed out that 2 Delta(o) is in almost linear proportion to k(B)T(max)(<< T*), where T-max is the temperature exhibiting a broad peak in chi-T curves and k(B)T(max) can be considered to give a measure of the effective antiferromagnetic ex change energy J(eff). The alpha factors in 2 Delta(o) similar to alpha k(B)T(max) similar to alpha J(eff) are similar to 1 for La214 and similar to 2 for Bi2212, respectively. We also report that in both Bi2212 and La214 systems T-c roughly scales with p Delta(o) except in highly doped samples, where T-c proportional to 2 Delta(o).
• 24aPS-19 La_<2-x>Sr_xCuO_4のT_c付近での電子比熱

  梅山 貴博, 松崎 俊明, 永田 敏夫, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 54 (2) 454 -454 1999年09月03日
• 24pYD-4 Bi2212とLa214の擬ギャップ

  伊土 政幸, 小田 研 日本物理学会講演概要集 54 (2) 479 -479 1999年09月03日
• 26pYS-1 トンネル分光で見たLa214のアンダートーブ域における超伝導ギャップ

  小田 研, Dipasupil R.M, 西郷 悟, 桃野 直樹, 伊土 政幸, Ozyuzer L, Zasadzinski J, Gray K 日本物理学会講演概要集 54 (2) 558 -558 1999年09月03日
• 26pYS-2 La214とBi2212のT_c及びT^*付近における磁確率:異方性と磁場依存性

  西郷 悟, ディパスピル レイニア, 小田 研, 桃野 直樹, 伊土 政幸 日本物理学会講演概要集 54 (2) 558 -558 1999年09月03日
• 26pYS-3 電子比熱から見たLa214系の擬ギャップ

  松崎 俊明, 梅山 貴博, 永田 敏夫, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 54 (2) 558 -558 1999年09月03日
• 29a-L-1 La_<2-x>Sr_xCuO_4における電子比熱

  松崎 俊明, 桃野 直樹, 梅山 貴博, 永田 敏夫, 小田 研, 伊土 政幸 日本物理学会講演概要集 54 (1) 584 -584 1999年03月15日
• Bi2212、La214系における超伝導体ギャップと擬ギャップ(基研研究会「強結合超伝導-Pseudogapを中心として-」,研究会報告)

  伊土 政幸, 小田 研, 桃野 直樹 物性研究 72 (4) 426 -430 1999年
• Pseudogap behavior in the electronic specific heat of La_2-xSr_xCuO₄

  J. Low Temp. Phys. 117 (3/4) 353 -357 1999年 [査読無し][通常論文]
  
• Crossover behavior of in-plane and out-of-plane resistivity in La2-xSrxCuO4

  N. Momono, R. Dipasupil, H. Ishiguro, S. Saigo, T. Nakano, M. Oda, M. Ido Physica C: Superconductivity and its Applications 317-318 603 -606 1999年 [査読無し][通常論文]
   

  We report that the in-plane (ρab) and out-of-plane (ρc) resistivity of La214 deviate downward and upward from linear extrapolations of their high-T data below a certain temperature T*, respectively, which are very similar to the crossover behaviors of ρab and ρc arising from the pseudogap formations in Y123 and Bi2212. The crossover behavior of resistivity in La214 occurs around T* approx. Tco ≡ 2Δo/4.3 kB as in Bi2212, where 2Δo is the superconducting gap magnitude at T ≪ Tc. These results suggest that a pseudogap may open up below T* approx. Tco also in La214, although it has not been observed in microscopic experiments on La214.
• Effects of Zn substitution on magnetic properties and superconductivity in La2-xSrxCuO4

  T. Nakano, N. Momono, T. Matsuzaki, T. Nagata, M. Yokoyama, M. Oda, M. Ido Physica C: Superconductivity and its Applications 317-318 575 -578 1999年 [査読無し][通常論文]
   

  In La2-xSrxCu1-yZnyO4, the superconductivity is locally suppressed through the disturbance of Cu 3dx(2)-y(2)-spin correlation around each Zn site. The seriously suppressed region of the superconductivity extends over the antiferromagnetic correlation length ξAF around each Zn. The suppressed region shrinks with x because ξAF decreases with x, and probably, its size becomes much smaller than the superconducting correlation length ξs in x = 0.22 samples. In the x = 0.22 samples, the Zn substitution effect on the superconductivity can be described phenomenologically by the theory for a d-wave superconductor with the strong scattering centers in the unitarity limit.
• 31a-P-2 La214系の磁性と超伝導に対するCuサイト置換効果

  中野 亨, 桃野 直樹, 小田 研, 伊土 政孝, 山谷 和彦 日本物理学会講演概要集 53 (1) 574 -574 1998年03月10日
• 30p-PSA-11 La_<2-x>Sr_xCuO_4の高温電子比熱

  内山 佳則, 桃野 直樹, 横山 正幸, 中野 亨, 小田 研, 尹土 政幸 日本物理学会講演概要集 53 (1) 550 -550 1998年03月10日
• 30p-PSA-12 電子比熱からみたLa_<2-x>Sr_xCu_<1-y>Ni_yO_4における対破壊効果

  永田 敏夫, 桃野 直樹, 横山 正幸, 中野 享, 小田 研, 伊土 政幸 日本物理学会講演概要集 53 (1) 551 -551 1998年03月10日
• 2p-S-7 Bi2212とLa214における擬ギャップ(スピンギャプ)と超伝導

  石黒 久詞, 阿部 紀夫, 穂谷 克彦, 中野 亨, 桃野 直樹, 小田 研, 伊土 政幸, 酒井 彰 日本物理学会講演概要集 53 (1) 634 -634 1998年03月10日
• 高温超伝導体の擬ギャップと超伝導

  小田 研, 桃野 直樹, 中野 享, 伊上 政幸 日本物理学会誌 53 (3) 192 -196 1998年 [査読有り][招待有り]
   

  超伝導ギャップの性質はpairing相互作用の起源を反映することから, 銅酸化物高温超伝導体でも多くの手法で精力的に調べられている. 本稿では, STM/STSから見た銅酸化物における超伝導ギャップの大きさのキャリア・ドープ量依存性を紹介し, この結果を基に反強磁性相互作用とpairing機構の関連性, スピンギャップの起源と超伝導の関連性について議論する.
• Dependence of superconducting gap on hole doping level in La2-xSrxCuO4

  N. Momono, T. Nakano, M. Oda, M. Ido Journal of Physics and Chemistry of Solids 59 (10-12) 2068 -2070 1998年 [査読無し][通常論文]
   

  We re-examined the superconducting gap 2Δ0 of La2-xSrxCuO4 (x = 0.18 and 0.2) by using tunneling techniques. The gap magnitude 2Δ0 is in agreement with kBTmax, where kBTmax will give an effective exchange energy between Cu spins, indicating that the pairing mechanism would be magnetic in origin. The resistivity decreases more rapidly with lowering T below a temperature T*. We also report that T* agrees with the mean-field transition temperature TMF c, given by the relation 2Δ0 = 4.3 kBTMF c. © 1998 Elsevier Science Ltd. All rights reserved.
• 5p-YF-7 高温超伝導体の擬ギャップと超伝導 : STM/STSから

  小田 研, 伊土 政幸 日本物理学会講演概要集 52 (2) 611 -611 1997年09月16日
• 6p-T-8 La-Sr系における超伝導ギャップのSr濃度依存性

  阿部 紀夫, 阿部 倫久, 穂谷 克彦, 中野 享, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 52 (2) 640 -640 1997年09月16日
• 8a-T-2 La-Sr系のdホールの局材性と超伝導特性

  中野 亨, 桃野 直樹, 小田 研, 伊土 政幸, 山谷 和彦 日本物理学会講演概要集 52 (2) 714 -714 1997年09月16日
• 8a-T-6 低温電子比熱からみたLa_<2-x>Sr_xCu_<1-y>Zn_yO_4における対破壊効果

  横山 正幸, 中野 亨, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 52 (2) 715 -715 1997年09月16日
• 28p-K-9 Cuサイト置換効果から見たLa-Sr系の磁化率と超伝導

  中野 享, 桃野 直樹, 横山 正幸, 小田 研, 伊土 政幸, 山谷 和彦 日本物理学会講演概要集 52 (1) 576 -576 1997年03月17日
• 28p-K-3 STM/STSから見たBi2212の超伝導ギャップに対するドーピング効果

  穂谷 克彦, 窪田 亮, 真鍋 力, 中野 享, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集 52 (1) 575 -575 1997年03月17日
• TSFZ法によるBi2212単結晶作製とそのSTM/STS

  窪田 亮, 穂谷 克彦, 真鍋 力, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1996 (3) 390 -390 1996年09月13日
• 電子比熱と磁化率から見たLa_<2-x>Sr_xCu_<1-y>M_yO_4(M=Ga, Zn)の不純物効果

  舌崎 朝子, 横山 正幸, 中野 亨, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1996 (3) 569 -569 1996年09月13日
• Bi2212のSTM像とSTSからみた超伝導状態

  真鍋 力, 窪田 亮, 穂谷 克彦, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1996 (3) 569 -569 1996年09月13日
• La_<1.8-x>Nd_<0.2>Ba_xCuO_4の構造相転移と超伝導に対する圧力効果

  工藤 聡夫, 阿部 紀夫, 中野 享, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1996 (3) 351 -351 1996年09月13日
• La-Sr系の磁性と電気伝導および超伝導

  中野 享, 桃野 直樹, 横山 正幸, 舌崎 朝子, 小田 研, 伊土 政幸, 山谷 和彦 日本物理学会講演概要集. 秋の分科会 1996 (3) 351 -351 1996年09月13日
• STM/STS and electronic specific heat of high-T-c cuprates - Symmetry of the order parameter

  M Ido, M Oda, N Momono, C Manabe, T Nakano PHYSICA C 263 (1-4) 225 -231 1996年05月 [査読無し][通常論文]
   

  We investigated features of the superconducting gap of Bi2Sr2CaCu2O8+delta by STM/STS and La2-xSrxCuO4 by measuring the electronic specific heat C-el. STS spectra were measured in the same processes as in observations of STM images at low bias voltage eV(0) = 20 meV. The superconducting gap structure in the STS spectra can be explained very well in terms of a d(x2-y2) superconductor with an anisotropic Fermi surface within the k(x)-k(y) plane. In superconducting La2-xSrxCuO4 (0.16 less than or equal to x less than or equal to 0.22), the electronic specific heat C-el is found to exhibit a T-2 dependence at T much less than T-c, and substitution of 0.3-0.5% Zn for Cu changes the T-2 dependence into a quite different one, described by the sum of T linear and T-3 terms. These features of C-el give convincing evidence for a clean superconductor with lines of nodes in the gap.
• 1p-YK-1 低温電子比熱からみたLa_<2-x>Sr_xCuO_4に対する不純物効果(低温(高温超伝導・超伝導対称性))

  桃野 直樹, 栄田 朗宏, 中野 享, 舌崎 朝子, 工藤 聡夫, 小田 研, 伊土 政幸 日本物理学会講演概要集. 年会 51 (3) 443 -443 1996年03月15日
• 1p-YJ-14 La-Sr系の磁化率とCuサイト置換効果(低温(高温超伝導・輸送現象,置換効果))

  中野 享, 栄田 朗宏, 舌崎 朝子, 窪田 亮, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集. 年会 51 (3) 441 -441 1996年03月15日
• Electronic Specific Heat of La_2-x Sr_x Cu_1-y M_y O₄ (M=Ga, Zn) : Impurity Effects on a D-wave Superconductor

  Journal of Low Temperature Physics 105 521 1996年 [査読無し][通常論文]
  
• F Dependence of Spin Susceptibility of La_2-x Sr_x Cu O₄

  Journal of Low Temperature Physics 105 395 1996年 [査読無し][通常論文]
  
• Pressure Effect on Anomalous Suppress : on of Tc around X=1/8 in La_2-x Ba_x Cu O₄ and La_1.8-x Nd_0.2 Ba_x Cu O₄

  Journal of Low Temperature Physics, 105 311 1996年 [査読無し][通常論文]
  
• Atomic-Plane-Selective STM Imaging and STS on the Bi₂ Sr₂ Ca Cu₂ O_8+δ Cleaved Surface

  Journal of Low Temperature Physics 105 241 1996年 [査読無し][通常論文]
  
• 低温比熱からみたLa_<2-x>Sr_xCuO_4系の超伝導ギャップの対称性と不純物効果

  桃野 直樹, 栄田 朗宏, 坂本 隆真, 中野 享, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1995 (3) 413 -413 1995年09月12日
• Bi_2Sr_2CaCu_2O_<8+b>劈開面におけるSTM像のバイアス電圧依存性

  阿部 倫久, 真鍋 力, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1995 (3) 380 -380 1995年09月12日
• STM/STSからみたBi_2Sr_2CaCu_2O_<8+δ>の超伝導ギャップの対称性

  真鍋 力, 阿部 倫久, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1995 (3) 521 -521 1995年09月12日
• 高温超伝導体のSTM像と超伝導ギャップの対称性

  小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1995 (3) 466 -467 1995年09月12日
• 30p-L-12 低温比熱からみたLa_<2-x>Sr_xCuO_4に対する不純物効果

  三浦 靖, 桃野 直樹, 栄田 朗宏, 小田 研, 伊土 政幸 日本物理学会講演概要集. 年会 50 (3) 429 -429 1995年03月16日
• 28a-L-3 置換効果からみたLa_<2-x>Sr_xCuO_4の磁性と電気伝導

  中野 亨, 栄田 朗宏, 小田 研, 伊土 政幸 日本物理学会講演概要集. 年会 50 (3) 308 -308 1995年03月16日
• 高温超伝導体における最近のSTM・STSの進展

  小田 研 固体物理 30 (7) 651 -658 1995年 [査読有り][招待有り]
  
• LOW-TEMPERATURE ELECTRONIC SPECIFIC-HEAT IN LA2-XSRXCU1-YZNYO4

  N MOMONO, M IDO, T NAKANO, M ODA PHYSICA C 235 1739 -1740 1994年12月 [査読無し][通常論文]
   

  Electronic specific heat C-el at T less than or equal to 10 K was studied on La2-xSrx Cu1-yZn3O4 below and above the critical Zn-content y(c) at which the superconductivity disappears. The specific heat C-el of non-doped superconducting samples exhibits a T-2-dependence, peculiar to a d-wave superconductor. The T-linear component of C-el appears in Zn-doped superconducting samples, and its coefficient gamma increases markedly with Zn content. In samples with various Zn contents, the relation between T-c/T-cy=0 and gamma/gamma(y>yc) can be understood in terms of strong impurity scattering in a d-wave superconductor.
• 2a-PS-3 La系の磁化率と超伝導II

  中野 享, 津田 純一, 坂本 隆真, 桃野 直樹, 小田 研, 伊土 正幸 日本物理学会講演概要集. 秋の分科会 1994 (3) 218 -218 1994年08月16日
• 5a-YE-12 Bi系銅酸化物高温超電導体の低温STM像とSTS

  真鍋 力, 阿部 倫久, 小田 研, 伊土 正幸 日本物理学会講演概要集. 秋の分科会 1994 (3) 402 -402 1994年08月16日
• 5a-YE-2 低温電子比熱からみたLa_<2-x>Sr_xCuO_4系におけるクーパー対の対称性

  桃野 直樹, 中野 享, 三浦 靖, 栄田 朗宏, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1994 (3) 397 -397 1994年08月16日
• 3a-YD-1 イオン・チャネリング法で観た60K級及び90K級YBa_2Cu_3O_y の格子異常

  山谷 和彦, 芳賀 哲也, 岡島 吉俊, 阿部 寛, 小田 研 日本物理学会講演概要集. 秋の分科会 1994 (3) 263 -263 1994年08月16日
• 31a-PS-2 YBCO/(YPr)BCO/YBCOトンネル接合のI-V特性

  小田 研, Lew D.J, Beasley M.R 日本物理学会講演概要集. 年会 49 (3) 447 -447 1994年03月16日
• 31a-PS-1 Bi_2Sr_2CaCu_2O_<8+y>の低温STM/STS

  真鍋 力, 小田 研, 伊土 政幸 日本物理学会講演概要集. 年会 49 (3) 446 -446 1994年03月16日
• ランタン銅酸化物における超伝導と構造に対する圧力効果

  フィズィカビィ 194,2069 1994年 [査読無し][通常論文]
  
• STM Images and STS of Bi₂Sr₂CaCu₂O₈₊₈

  Physica C 235 797 1994年 [査読無し][通常論文]
  
• Pressure effect on superconductivity and structural transition in La_2-xSr_xCuO₄

  Physica B 194,2069 1994年 [査読無し][通常論文]
  
• 14a-E-5 La_<2-x>Sr_xCuO_4磁性と電気伝導

  中野 享, 三浦 靖, 桃野 直樹, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1993 (3) 453 -453 1993年09月20日
• 12p-PSA-24 La_<2-x-y>Nd_ySr_xCuO_4の低温構造相転移に対する圧力効果

  赤羽 修, 津田 純一, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1993 (3) 330 -330 1993年09月20日
• 12p-PSA-21 La-Ba系の低温比熱

  千田 健一郎, 桃野 直樹, 中野 享, 小田 研, 伊土 政幸 日本物理学会講演概要集. 秋の分科会 1993 (3) 329 -329 1993年09月20日
• 30p-PSB-54 La系の磁化率と超伝導に対するCuサイト置換効果II

  中野 享, 桃野 直樹, 真鍋 力, 小田 研, 伊土 政幸 日本物理学会講演概要集. 年会 48 (3) 343 -343 1993年03月16日
• 30p-PSB-31 La_<1.6-x>Nd_<0.4>Sr_xCuO_4の低温構造相転移に対する圧力効果

  赤羽 修, 桃野 直樹, 千田 健一郎, 小田 研, 伊土 政幸 日本物理学会講演概要集. 年会 48 (3) 332 -332 1993年03月16日
• 29a-W-13 La_<2-x>Sr_xCu_<1-y>Zn_yO_4の電子比熱係数

  桃野 直樹, 千田 健一郎, 中野 享, 小田 研, 伊土 政幸 日本物理学会講演概要集. 年会 48 (3) 247 -247 1993年03月16日
• 27a-PS-4 La系の低ホール濃度領域における磁化率の温度変化

  鎌田 賢明, 中野 亨, 真鍋 力, 小田 研, 伊土 政幸 秋の分科会講演予稿集 1992 (3) 376 -376 1992年09月14日
• 27a-PS-1 La系の低温構造相転移に対する圧力効果

  山田 修史, 赤羽 修, 千田 健一郎, 桃野 直樹, 小田 研, 伊土 政幸 秋の分科会講演予稿集 1992 (3) 375 -375 1992年09月14日
• 28p-Q-1 La_<2-x>Sr_xCuO_4の電子比熱係数から見た構造と超伝導

  桃野 直樹, 千田 健一郎, 小田 研, 伊土 政幸, 岡島 吉俊, 山谷 和彦 秋の分科会講演予稿集 1992 (3) 422 -422 1992年09月14日
• 28a-Q-8 La系の磁化率と超伝導に対するCuサイト置換効果

  中野 亨, 鎌田 賢明, 真鍋 力, 小田 研, 伊土 政幸 秋の分科会講演予稿集 1992 (3) 419 -419 1992年09月14日
• 30p-A-14 La_<2-x>Sr_xCuO_4の結晶構造とT_cの圧力効果

  山田 修史, 瀬川 裕一, 小田 研, 伊土 政幸 年会講演予稿集 47 (3) 366 -366 1992年03月12日
• Coefficient of Electronic Specific Heat in La_<2-x>Ba_xCuO_4 and La_<1.91>Ba_<0.09>Cu_<1-y>Zn_yO_4 : II-A Instability and Substitution Effects : II Oxide Superconductors; Experiments II : Electronic States :

  OKAJIMA Yoshitoshi, YAMAYA Kazuhiko, YAMADA Naofumi, ODA Migaku, IDO Masayuki JJAP series 7 103 -105 1992年
• La_2-XM_XCuO₄(M=Sr,Ba)におけるホールドーピングと帯磁率の温度変化

  固体物理 27 1992年 [査読有り][招待有り]
  
• Hole-doping and magnetic susceptibility in La_2-XM_XCuO₄ (M=Sr, Ba)

  27 1992年 [査読無し][通常論文]
  
• 30p-APS-13 (La_<1-x>Ba_x)_2CuO_4系における低温構造と超伝導

  伊土 政幸, 桃野 直樹, 山田 修史, 瀬川 裕一, 小田 研, 小野寺 彰 年会講演予稿集 46 (3) 397 -397 1991年09月12日
• 27a-ZL-13 La系の磁化率と超伝導

  小田 研, 鎌田 賢明, 中野 享, 伊土 政幸 年会講演予稿集 46 (3) 244 -244 1991年09月12日
• 25a-PS-1 (La_<1-x>M_x)_2CuO_4(M=Ba, Sr)の構造相転移と電気的・磁気的性質II

  山田 修史, 小田 研, 松木 英夫, 瀬川 裕一, 伊土 政幸 春の分科会講演予稿集 1991 (3) 259 -259 1991年03月11日
• (La_<1-x>M_x)_2CuO_4 (M=Ba,Sr)の構造相転移と電気的・磁気的性質

  山田 修史, 小田 研, 松木 英夫, 瀬川 裕一, 伊土 政幸 秋の分科会講演予稿集 1990 (3) 230 -230 1990年10月02日
• 31a-TC-5 (La_<1-X>Ba_X)_2CuO_4の構造相転移と低温比熱

  岡島 吉俊, 山谷 和彦, 小田 研, 伊土 政幸 年会講演予稿集 45 (3) 225 -225 1990年03月16日
• 31a-TC-6 (La_<1-x>M_x)_2CuO_4 (M=Ba, Sr)の超伝導と構造相転移に対する圧力効果

  山田 修史, 小田 研, 伊土 政幸 年会講演予稿集 45 (3) 226 -226 1990年03月16日
• 31p-PS-81 Bi_2Sr_2Ca_<1->, Y, Cu_2O_8の磁化率の温度変化と超伝導

  松木 英夫, 小田 研, 伊土 政幸 年会講演予稿集 45 (3) 266 -266 1990年03月16日
• 31p-PS-40 La_2CuO_4の磁性と電気伝導 II

  小田 研, 伊土 政幸, 日高 義和, 鈴木 実, 村上 敏明 年会講演予稿集 45 (3) 247 -247 1990年03月16日
• MAGNETIC-SUSCEPTIBILITY AND SUPERCONDUCTIVITY IN (LA1-XSRX)2CUO4

  M ODA, T OHGURO, N YAMADA, M IDO JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 58 (4) 1137 -1140 1989年04月 [査読無し][通常論文]
  
• 31a-PS-78 高ホール濃度領域における(La_<1-x>Sr_x)_2CuO_4の熱起電力(低温(酸化物超伝導))

  吉本 直人, 小田 研, 日高 義和, 田嶋 幸道, 疋田 真, 鈴木 実 年会講演予稿集 44 (3) 284 -284 1989年03月28日
• 31p-PS-1 (La_<1-x>Sr_x)_2CuO_4の超伝導(低温(酸化物超伝導))

  小田 研, 大黒 達也, 山田 修史, 伊土 政幸 年会講演予稿集 44 (3) 248 -248 1989年03月28日
• 5a-PS-36 収束電子回折法によるBi-Sr-Ca-Cu-O系の空間群の決定

  津田 健治, 田中 通義, 遼藤 康夫, 日高 義和, 小田 研, 鈴木 実, 村上 敏明 秋の分科会講演予稿集 1988 (3) 232 -232 1988年09月16日
• 5p-PS-44 (La_<1-x>Sr_x)_2CuO_<4-y>単結晶における超伝導体積比率の増加

  日高 義和, 小田 研, 鈴木 実, 村上 敏明 秋の分科会講演予稿集 1988 (3) 256 -256 1988年09月16日
• 5p-PS-28 陽電子消滅による高温超伝導体のフェルミ面の決定

  谷川 庄一郎, 栗原 俊一, 大沢 真人, 水原 洋治, 日高 義和, 小田 研, 榎本 陽一, 鈴木 実, 村上 敏明 秋の分科会講演予稿集 1988 (3) 248 -248 1988年09月16日
• 5p-PS-43 La_2CuO_4の磁気抵抗

  小田 研, 日高 義和, 鈴木 実, 村上 敏明 秋の分科会講演予稿集 1988 (3) 255 -255 1988年09月16日
• 31p-C-3 酸化物高温超伝導体単結晶の育成(主題:高温超伝導体の結晶作成,結晶成長シンポジウム)

  日高 義和, 小田 研, 鈴木 実, 村上 敏明 年会講演予稿集 43 (2) 6 -8 1988年03月31日
• 1p-PS-43 陽電子消滅による(La_<1-x>Sr_x)_2CuO_4のフェルミ面(低温(酸化物超伝導体))

  水原 洋治, 谷川 庄一郎, 日高 義和, 小田 研, 鈴木 実, 村上 敏明 年会講演予稿集 43 (3) 228 -228 1988年03月18日
• 1p-PS-60 (La_<1-x>Sr_x)_2CuO_4単結晶の電気特性(低温(酸化物超伝導体))

  日高 義和, 小田 研, 鈴木 実, 榎本 隅一, 村上 敏明 年会講演予稿集 43 (3) 235 -235 1988年03月18日
• 1p-PS-61 Ba_2YCu_3O_<7-y>単結晶薄膜の光学特性(低温(酸化物超伝導体))

  小田 研, 榎本 隅一, 鈴木 実, 村上 敏明 年会講演予稿集 43 (3) 236 -236 1988年03月18日
• Neutron Magnetic Scattering Studies from Pure and Doped La_2CuO_4 : I. Oxides :

  Y Endoh, K Yamada, E Kudo, Y Hidaka, M Oda, Y Enomoto, M Suzuki, T Murakami, R J Birgeneau, D R Gabbe, H P Jenssen, M A Kastner, C J Peters, P J Picone, T R Thurton, G Shirane, J M Tranquada JJAP series 1 24 -27 1988年
• Static and dynamic spin correlations in pure and doped La2CuO4

  Y. Endoh, K. Yamada, R. J. Birgeneau, D. R. Gabbe, H. P. Jenssen, M. A. Kastner, C. J. Peters, P. J. Picone, T. R. Thurston, J. M. Tranquada, G. Shirane, Y. Hidaka, M. Oda, Y. Enomoto, M. Suzuki, T. Murakami Physical Review B 37 (13) 7443 -7453 1988年 [査読無し][通常論文]
   

  We report elastic, quasielastic (F dE), and inelastic neutron-scattering studies of the instantaneous and dynamic spin fluctuations in as-grown and doped La2CuO4. Four samples have been studied: (A) as-grown La2CuO4 with TN=195 K, (B) oxygenated La2CuO4 with TN100 K, (C) La2Cu0.95Li0.05O4, and (D) La1.97Sr0.03Cu0.95Li0.05O4. All crystals exhibit variable-range-hopping conductivity behavior. At room temperature each sample exhibits two-dimensional (2D) antiferromagnetic instantaneous correlations in the CuO2 sheets with correlation length varying from 200 AI in crystal A to 14 AI in crystal D. The integrated intensity and therefore the effective moment is, however, constant to within the experimental error. In samples A and B the 2D correlation length becomes sufficiently large with decreasing temperature that the interplanar coupling is able to drive a transition to 3D long-range order. The spin dynamics have been studied in detail in crystals A and B and quite unusual behavior is observed. In contrast to previously studied planar antiferromagnets, there is no significant E0 component for temperatures TN and instead the 2D response function is highly inelastic. The effective dispersion of the spin excitations is 0.4 eV A. This large energy scale for the spin fluctuations gives credence to models of the superconductivity in doped La2CuO4 in which the pairing is magnetic in origin. © 1988 The American Physical Society.
• Antiferromagnetic spin correlations in insulating, metallic, and superconducting La2-xSrxCuO4

  R. J. Birgeneau, D. R. Gabbe, H. P. Jenssen, M. A. Kastner, P. J. Picone, T. R. Thurston, G. Shirane, Y. Endoh, M. Sato, K. Yamada, Y. Hidaka, M. Oda, Y. Enomoto, M. Suzuki, T. Murakami Physical Review B 38 (10) 6614 -6623 1988年 [査読無し][通常論文]
   

  We have carried out elastic, quasielastic (∫dE), and inelastic neutron scattering studies of the antiferromagnetic spin correlations in La2-xSrxCuO4 with x varying between 0.02 and 0.18. The crystals, which were grown in three different laboratories, exhibit behavior that varies smoothly with x. In all cases, antiferromagnetic correlations with a scattering amplitude corresponding to a fully occupied Cu2+ square lattice are observed. However, the Néel state is destroyed by the doping and the spin-spin correlation length ξ is quite short, varying from 35 to 8 Å as x varies between 0.02 and 0.18 the local order is, however, the same as in pure La2CuO4. The fluctuations are dynamic in character as in La2CuO4 above the Néel temperature TN. To a first approximation, ξ=3.8x, the average separation between the holes introduced by the Sr2+ doping. The x=0.08 sample exhibits superconductivity with Tc=10 K and with a Meissner fraction exceeding 15% at 5 K no important differences in the magnetic scattering are observed in the normal and superconducting states. In an appendix we present additional data on the spin dynamics in pure La2CuO4 at Tc=300 K in a sample with TN=235 K. © 1988 The American Physical Society.
• Determination of Space Group and Refinement of Structure Parameters for La2CuO4-δ Crystals

  Yamada Kazuyoshi, Kudo Eisuke, Endoh Yasuo, Tsuda Kenji, Tanaka Michiyoshi, Kokusho Koichi, Asano Hajime, Izumi Fujio, Oda Migaku, Hidaka Yoshikazu, Suzuki Minoru, Murakami Toshiaki Jpn J Appl Phys 27 (7) 1132 -1137 1988年 [査読無し][通常論文]
   

  The space group in the orthorhombic phase of La2CuO4-δ was confirmed to be Cmca for both as grown and deoxygenated crystals by using conventional and convergent beam electron diffraction together with high resolution neutron powder diffraction methods. The Rietveld refinements of neutron powder diffraction data determined the structural parameters. Slight differences in lattice constants, positional parameters and occupation factor for oxygen atoms were found between the two crystals.
• 27p-PS-34 La-Cu-Oの超伝導

  村上 敏明, 小田 研, 日高 義和, 鈴木 実, 榎本 陽一 秋の分科会講演予稿集 1987 (3) 225 -225 1987年09月16日
• 27p-PS-35 (La_<1-x>Sr_x)_2CuO_<4-u>及びBa_2YCu_3O_<7-u>単結晶の電気的磁気的異方性

  日高 義和, 小田 研, 鈴木 実, 村上 敏明 秋の分科会講演予稿集 1987 (3) 225 -225 1987年09月16日
• 27p-PS-5 収束電子回折法によるLa_2CuO_<4-δ>の空間群の決定

  津田 健治, 田中 通義, 山田 和芳, 遠藤 康夫, 日高 義和, 小田 研, 鈴木 実, 村上 敏明 秋の分科会講演予稿集 1987 (3) 199 -199 1987年09月16日
• 27p-PS-9 La_2CuO_<4-δ>単結晶の磁性と酸素欠陥

  山田 和芳, 遠藤 康夫, 工藤 栄亮, 小田 研, 日高 義和, 鈴木 実, 村上 敏明 秋の分科会講演予稿集 1987 (3) 201 -201 1987年09月16日
• 27p-PS-33 (La_<1-x>Sr_x)_2CuO_4, Ba_2YCu_3O_<7-δ>単結晶薄膜の光学特性

  小田 研, 鈴木 実, 森脇 和幸, 榎本 陽一, 村上 敏明 秋の分科会講演予稿集 1987 (3) 224 -224 1987年09月16日
• 30p-LC-3 BaPb_<1-x>Bi_xO_3結晶構造の熱処理効果(低温)

  小田 研, 日高 義和, 村上 敏明 年会講演予稿集 42 (3) 280 -280 1987年03月27日
• CRITICAL CURRENT AND STABILITY OF EPITAXIALLY GROWN BA2YCU3O7-Y THIN-FILMS

  T MURAKAMI, Y ENOMOTO, M SUZUKI, K MORIWAKI, M ODA JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 26 2037 -2037 1987年 [査読無し][通常論文]
  
• Anisotropic Upper Critical Magnetic Field in Single Crystal Ba2YCu3O7-y

  Y. Hidaka, M. Oda, M. Suzuki, A. Katsui, T. Murakami, N. Kobayashi, Y. Muto Physica B 148 (1/3) 329 -331 1987年 [査読無し][通常論文]
  
• 27a-RB-9 BaBiO_3のEXAFS

  小田 研, 前山 智, 村上 敏明 秋の分科会講演予稿集 1986 (3) 255 -255 1986年09月12日
• 27a-RB-8 BaPb_<1-x>Bi_xO_3の結晶構造

  村上 敏明, 小田 研, 日高 義和, 勝井 明憲 秋の分科会講演予稿集 1986 (3) 254 -254 1986年09月12日
• CONDUCTION NOISE UNDER PULSED ELECTRIC-FIELD IN NONOHMIC REGIME OF NBSE3

  M IDO, Y OKAJIMA, M ODA JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 55 (7) 2106 -2109 1986年07月 [査読無し][通常論文]
  
• 29a-CA-8 BaPb_<1-x>Bi_xO_3(BPB)多結晶体の電気抵抗の異常(低温)

  村上 敏明, 鈴木 実, 小田 研 年会講演予稿集 41 (3) 208 -208 1986年03月29日
• 29a-CA-2 BaPb_<1-x>Bi_xO_3のX線構造解析(低温)

  仙場 浩一, 小田 研, 日高 義和, 勝井 明憲, 村上 敏明 年会講演予稿集 41 (3) 205 -205 1986年03月29日
• 2p-B-2 BaPb_<1-x>Bi_xO_3の構造相転移II

  小田 研, 日高 義和, 勝井 明憲, 村上 敏明 秋の分科会講演予稿集 1985 (3) 209 -209 1985年09月13日
• 4a-F-4 しきい電場が強い温度依存性を示すNbSe_3での非線形電気伝導

  脇本 啓嗣, 伊土 政幸, 三本木 孝, 小田 研 秋の分科会講演予稿集 1985 (2) 197 -197 1985年09月13日
• 4a-F-5 NbSe_3の非線形領域におけるノイズ

  岡島 吉俊, 伊土 政幸, 小田 研 秋の分科会講演予稿集 1985 (2) 197 -197 1985年09月13日
• 31p-B1-2 BaPb_<1-x>Bi_xO_3の構造相転移(低温)

  小田 研, 日高 義和, 勝井 明憲, 村上 敏明 年会講演予稿集 40 (3) 223 -223 1985年03月31日
• 5a-A-1 Nb_<1-x>M_xSe_3(M=Ta,Ti)における非線型電気伝導度

  脇本 啓嗣, 川端 和重, 伊土 政幸, 三本木 孝, 小田 研 秋の分科会講演予稿集 1984 (2) 219 -219 1984年09月10日
• Depinning of the Charge-Density Wave in NbSe_3(EXPERIMENTS ON MX_3 COMPOUNDS, International Symposium on NONLINEAR TRANSPORT AND RELATED PHENOMENA IN INORGANIC QUASI ONE DIMENSIONAL CONDUCTORS) :

  Oda M., Ido M. 物性研究 41 (4) 161 -178 1984年 

  In the non-Ohmic regime of NbSe_3, an evidence that the charge-density wave (CDW) slides as a whole over the whole crystal is obtained by investigating both the transient conductivity under pulsed field and the periodic noise. It is also confirmed that the configuration of the CDW changes as it begins to slide.
• 13p-PS-24 NbSe_3におけるCDWの運動I

  小田 研, 伊土 政幸, 三本木 孝 秋の分科会講演予稿集 1983 (2) 202 -202 1983年09月13日
• 13p-PS-23 NbSe_3におけるCDWの運動II

  伊土 政幸, 小田 研, 三本木 孝 秋の分科会講演予稿集 1983 (2) 202 -202 1983年09月13日
• 30p-B-1 NbSe_3の高電場領域における非線型電気伝導

  小田 研, 伊土 政幸, 川端 和重, 三本木 孝 年会講演予稿集 37 (2) 128 -128 1982年09月14日

共同研究・競争的資金等の研究課題

• 特異点光波による光誘起ナノスケール超伝導の創製

  日本学術振興会：科学研究費助成事業

  研究期間 : 2022年04月 -2025年03月 

  代表者 : 戸田 泰則, 小田 研, 土屋 聡
• 実空間と時間の両領域で見る銅酸化物における擬ギャップ状態と高温超伝導の関わり

  日本学術振興会：科学研究費助成事業

  研究期間 : 2019年04月 -2023年03月 

  代表者 : 小田 研, 戸田 泰則

   

  銅酸化物高温超伝導体における電子系の大きな特徴の一つはフェルミ面の二分性であり、そのフェルミ面は擬ギャップ(PG)が発達するゾーン境界付近の領域(アンタイノード(AN)領域)と超伝導ギャップ(SCG)が開くアーク状の領域(フェルミアーク(FA))に分けられる。本研究では、実空間と時間空間の双方から「PGを伴う電子状態と高温超伝導の発現との関係性の解明」を目的として、Bi系銅酸化物高温超伝導体Bi2212で走査トンネル顕微鏡分光(STM/STS)とポンプ・プローブ時間分解分光(PPTS)を行っている。本年度に得られた成果の概要を以下に記す。 １．STM/STSによる研究では、AN領域における２種類の電子系変調構造(ペアリングギャップ程度の低エネルギー状態(ペア密度波(PDW)状態)を反映するチェッカーボード変調(CB変調)とPG程度の高エネルギー状態を反映するｄ構造因子密度波(dFF-DW))の共存関係について詳細に調べ、両者は変調構造を特徴づける局所振幅と局所位相という点で強い実空間相関を示すことが明らかとなった。この結果は、CB変調とFA上の準粒子干渉(QPI)による変調との強い実空間相関(前年度に得られた成果)を考え合わせると、Bi2212の３種類の電子系変調構造は実空間で相互に関わっていることを示唆するものと考えられる。 ２．PPTSによる研究では、高強度超短パルス光照射によりBi2212のPGとSCGを局所的に破壊し、その後の両者の形成過程を時間分解で調べている。今年度は、最適キャリア濃度のBi2212でPGの発達を制御してPPTSを行った結果、PGの発達の程度に関わらず、FAでのSCGの形成はAN領域のPGが完全に回復してから始まること、すなわち、両者の形成過程に明確な時間相関があり、超伝導はPG状態と時間空間においても共存して起こることが明らかとなった。
• 光渦パルスで実現する時空間超伝導相制御

  日本学術振興会：科学研究費助成事業

  研究期間 : 2019年04月 -2022年03月 

  代表者 : 戸田 泰則, 小田 研, 土屋 聡

   

  超短パルス光を用いて超伝導を構成する電子対をすべて励起すると、常伝導への瞬時的かつ非熱的なクエンチ（コヒーレントクエンチ）を誘起できる。本研究ではビーム断面内に特徴的な空間特性を有する光渦パルスを使ってコヒーレントクエンチを誘起することにより、時空間で変調された新しい超伝導状態の創出とその観測および制御を実現した。本成果は光波の空間制御性を活用した新しいタイプの物質制御を確立したことに対応し、ナノスケール物性探索や超伝導デバイス開発への応用につながる。
• 実空間と運動量空間の双方から見た銅酸化物高温超伝導と擬ギャップに対する不純物効果

  日本学術振興会：科学研究費助成事業

  研究期間 : 2015年04月 -2018年03月 

  代表者 : 小田 研, 黒澤 徹, 吉田 紘行

   

  本研究では、銅酸化物における高温超伝導の発現機構や擬ギャップ現象の起源と反強磁性相互作用との関わりに関する知見を得ることを目的として、Bi系銅酸化物の純粋な試料および少量のNiをCuサイトに添加した試料において低温（T<
• ビスマス系高温超伝導体における光誘起超伝導相転移ダイナミクスの研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 2012年04月 -2015年03月 

  代表者 : 戸田 泰則, 小田 研

   

  ビスマス系高温超伝導体における超伝導と擬ギャップの光誘起相転移ダイナミクスを超短パルス光を用いて調査し、1)擬ギャップが自発的対称性破れを伴うこと、2)超伝導ギャップ形成と位相コヒーレンスの関係性、3)擬ギャップ形成ダイナミクスが長距離秩序を持たない局在状態を反映すること、4)アンダードープ領域において超伝導秩序形成における擬ギャップの相関が強まることを明らかにした。
• 走査トンネル顕微鏡による銅酸化物高温超伝導体の磁場誘起電荷秩序に関する研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 2010年04月 -2012年03月 

  代表者 : 小田 研, 戸田 泰則, 伊土 政幸

   

  本研究では、銅酸化物高温超伝導体に特徴的な擬ギャップを伴った電子系電荷秩序の起源と高温超伝導との関係を明らかにするために、その代表物質の一つであるBi2212で磁場中STM/STS実験とポンプ・プローブ分光実験を行った。STM/STS実験では、Bi2212の電荷秩序が、電荷とスピンのストライプに由来すること、また、バルクの性質としては揺らいだ状態にあることを示唆する結果が得られた。ポンプ・プローブ分光実験では、擬ギャップ・電荷秩序は、超伝導と単なる競合関係にあるのではなく、超伝導の発現に必要な電子系の性質であることが明らかとなった。これらの結果を考え合わせると、ストライプ秩序の揺らぎが高温超伝導の機構に深く関っている可能性があると結論できる。
• STM・STSから見たBi系銅酸化物超伝導体の電荷秩序と2種類の擬ギャップ構造

  日本学術振興会：科学研究費助成事業

  研究期間 : 2010年04月 -2012年03月 

  代表者 : 伊土 政幸, 小田 研, 桃野 直樹

   

  本研究では、STM/STSのdI/dV像やLDOS像からBi系銅酸化物高温超伝導体の大きな擬ギャップに関連するCu-O面の電荷秩序を調べた。その結果、1)電荷秩序はエネルギーギャップ内の低エネルギー領域で超伝導の準粒子干渉と共存すること、2)電荷秩序の周期はドープ量(ホール濃度)と共に格子定数の整数倍で変化する傾向にあること、また3)電荷秩序の明るい領域では暗い領域に比べてドープ量が高くなっていることが分かった。これらの結果は、電荷秩序がストライプモデルで見られるようなCu-O面内のホールの再配列に起因することを示している。また、本研究では小さな擬ギャップと超伝導との関わりについても議論した。
• 巨大近接効果ジョセフソン素子の研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 2005年04月 -2006年03月 

  代表者 : 小田 研, 伊土 政幸, 桃野 直樹, 丹田 聡, 浅野 泰寛

   

  本研究は、銅酸化物高温超伝導体における巨大近接効果の起源を解明し、これを用いた新規なタイプのジョセブソン接合を作製することを目的とする。巨大近接効果には、高温超伝導体の特異な性質の一つである擬ギャップ状態が深く関わっていると考えられている。そこで本研究では、擬ギャップ状態の起源に関する知見を得るため、走査トンネル顕微鏡(STM)によりビスマス系銅酸化物高温超伝導体(Bi2212)の擬ギャップを詳しく調べた。その結果、特性エネルギーが擬ギャップである電荷秩序の存在が明らかとなり、擬ギャップは電荷秩序の形成によることが示された。また、この電荷秩序は、d波超伝導ギャップのノードから離れた、いわゆるアンチノード領域の電子状態が関わっていて、T_C以下の超伝導状態でも存続し、ノード付近のフェルミ面(フェルミアーク)領域の準粒子によって起こる超伝導(フェルミアーク超伝導)と共存することも明らかにされた。アンチノード領域の準粒子、あるいは、それらの対(インコヒーレントなクーパー対)が電荷秩序を担うと考えられるが、どちらに起因するかは今後明らかにされるべき大変興味深い問題である。さらに、本研究では、クーパー対の電荷秩序、いわゆる"ボソン結晶"が高温超伝導体で実現していると、これが低温で超流動性を示す可能性(固体超流動の可能性)のあることが指摘され、このことと巨大近接効果の起源との関連性が議論された。 これらの成果については、日本物理学会や高温超伝導に関する幾つかの国際会議で既に報告し、また、論文としてPhys. Rev. Lett.誌などに投稿した。
• 高磁場STM・STSによる高温超伝導体の磁束格子観察と磁束内反強磁性秩序の研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 2003年04月 -2005年03月 

  代表者 : 小田 研, 桃野 直樹

   

  ランタン系銅酸化物高温超伝導体La_<2-x>Sr_xCuO_4(La214)の超伝導状態で磁場を印加すると反強磁性秩序が誘起され、それが超伝導と共存することが、中性子散乱実験から報告された。また、ビスマス系銅酸化物高温超伝導体Bi_2Sr_2CaCu_2O_<8+δ>(Bi2212)の走査トンネル顕微鏡(STM)・トンネル分光(STS)実験から、磁束芯における電子系のエネルギースペクトルが超伝導転移温度T_cより高温のノーマル状態と同様なギャップ様構造(擬ギャップ)を示すことが明らかにされている。さらに、磁束芯を中心として4a×4aの変調構造が発達することも報告されており、この変調構造が磁場誘起反強磁性秩序と関係するものと考えられている。本研究では、磁場誘起反強磁性秩序の起源、擬ギャップの起源、そして、超伝導の発現機構に関する知見を得るために、Bi2212における4a×4aの変調構造についてSTM/STSの実験から調べた。 1.Bi2212の擬ギャップ状態で4a×4aの電荷秩序が観測される試料とされない試料が存在することが明らかとなった。 2.電荷秩序がより強く観測される試料ほど擬ギャップのサイズが空間的に不均一になっていることも明らかになった。 これらの結果は、"擬ギャップ状態で観測される電荷秩序は、本来動的に揺らいでいるが、電子状態に不均一をもたらす散乱源があると、これがピン止中心となるために動的な電荷秩序は静的なものになる"ことを意味している。これまでにも「4a×4aの電荷秩序が高温超伝導体の擬ギャップ状態における隠れた秩序である」と主張されているが、本研究の結果はこのことを強く支持するものである。磁場中では磁束線がピン止中心となって静的な4a×4a電荷秩序が安定になっていると言えるが、この電荷秩序は反強磁性的な磁気秩序を伴っているものと考えられる。
• 鋼酸化物高温超伝導体における擬ギャップと凝集エネルギーの研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 2000年04月 -2003年03月 

  代表者 : 伊土 政幸, 桃野 直樹, 小田 研

   

  高温超伝導の発現を考える上で前駆現象である"小さな擬ギャップ"の果たす役割を理解することが非常に重要である。これまで我々は、常伝導相の電子比熱係数の振る舞いやT_cまでフェルミ準位にエネルギーギャップが残ることなどからLa214系でも小さな擬ギャップが成長することを指摘してきたが、最近、中性子散乱実験やNMRの緩和時間でその直接的証拠が報告された。また、角度分解光電子分光実験からLa214系のフェルミ面もBi2212系と同様に擬ギャップの形成に伴って(π/2,π/2)近傍を中心とするアーク状(フェルミアーク)になることが明らかにされた。一方、高温超伝導体ではアンダードープ領域で超伝導の凝集エネルギーU(0)が大きく減少することが知られている。これまでに我々は「U(0)の大きな減少は小さな擬ギャップが成長すると超伝導の特性エネルギーがΔ_0からβpΔ_0(β=constでpはホール濃度)に変わることで説明できる」ことをLa214系について示してきたが、本年度は、より広いホール濃度についてこの点を確認した。そしてNMRのナイトシフトの結果等も参考にして「超伝導の特性エネルギーの変化は、小さな擬ギャップの成長に伴って形成されるフェルミアークと関連している」ことを指摘した。しかし、擬ギャップの成長が顕著となるアンダードープ領域では超伝導相と常伝導相との相分離が起こり、このためU(0)が大きく減少するとの指摘がある。このため、Bi2212系の走査トンネル分光(STM/STS)実験から超伝導のナノスケールでの一様性も調べたが、T_cはまだ高いがU(0)は大きく減少する少しアンダードープ域ではそのような相分離は見られないことを明らかにした。
• 走査トンネル分光による高温超伝導体の電子対コヒーレンスの起源に関する研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 2001年 -2003年 

  代表者 : 伊土 政幸, 桃野 直樹, 小田 研

   

  高温超伝導体の常伝導相(T>T_c)では、k空間の(π,0)と(0,π)近傍のフェルミ面に超伝導ギャップとほぼ同じ大きさの"小さな擬ギャップ"が成長し、T_c付近では(π/2,π/2)近傍にアーク状のフェルミ面が残ることが知られている。本研究では、Bi2212のトンネル分光実験から小さな擬ギャップはd波超伝導体の平均場の臨界温度付近から急速に成長し、T_cで超伝導状態のギャップにほぼ連続的に移行すること、また、ARPESの結果と同様に小さな擬ギャップの成長は低ホール濃度ほど顕著となることを確認した。ところで、T_c近傍でアーク状となるフェルミ面のキャリアーは、大きな面内易動度を持つことから、超伝導をもたらすクーパー対のコヒーレントな運動との関連で大きな興味が持たれている。そこで、本研究では超伝導の凝集エネルギーU(0)とトンネルスペクトルのコヒーレンスピークが低ホール濃度領域で共に大きく抑制される点に着目し、フェルミアークと超伝導との関連性を調べた。特に、U(0)はLa214系の電子比熱から、小さな擬ギャップとの関連性に注意しながら系統的に研究を行った。その結果、コヒーレントな運動をするクーパー対は「フェルミアーク上のホールから作られるものに限られる」と考えると、低ホール濃度領域でのU(0)とコヒーレンスピークの大きな抑制が良く理解できることを示した。しかし、小さな擬ギャップの成長が顕著となるアンダードープ領域では、超伝導相と常伝導相との相分離が起こるためにU(0)が大きく減少するとの指摘がある。そこで、Bi2212系の走査トンネル分光(STM/STS)実験からナノスケールで超伝導の一様性を詳しく調べ、U(0)の大きな減少が相分離に起因するものでない点を確認し、擬ギャップ領域での電子対コヒーレンスの起源はフェルミアークにあると結論した。
• 走査トンネル顕微鏡による銅酸化物の擬ギャッ プと超伝導臨界温度の制御に関する研究

  公益財団法人 日立財団：倉田奨励金

  研究期間 : 2000年04月 -2001年03月 

  代表者 : 小田 研
• 走査トンネル顕微鏡による高温超伝導体のアンドレーエフ反射と擬ギャップの研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 2000年04月 -2001年03月 

  代表者 : 小田 研, 桃野 直樹, 伊土 政幸

   

  本研究では、ビスマス系銅酸化物Bi2212とランタン系銅酸化物La214とで走査トンネル顕微鏡STMを用いてトンネル分光とアンドレーエフ反射の実験を行い、次のような結果を得た。 1)トンネル分光に関する実験では、超伝導転移温床T_cより高温の2つのクロスオーバー温度(T_及びT^*)と関係する2種類の擬ギャップ(LPG及びSPG)が、電子のエネルギー・スベクトルに存在することが明らかになった。 2)T_付近から発達するLPGは、低温(T<は、T_cでスケールされることが示唆された。 以上の結果は、角度分解光電子分光(ARPES)の実験で報告されているk-空間における擬ギャップの発展に関する知見を考え合わせると、T_c以下でk-空間のコールド・スポット部分((π/2,π/2)付近)に形成されるエネルギー・ギャップの大きさがΔ_程度になること、そして、コールド・スポット部分のホールが超伝導の発現(電子(ホール)対コヒーレンスの長距離秩序)に深く係っていることを意味しており、高温超伝導の機構に関する興味深い知見を与えている。
• 走査トンネル顕微鏡によるZhang-Rice一重項の直接的検証と高温超伝導の研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1997年04月 -1999年03月 

  代表者 : 小田 研, 桃野 直樹, 伊土 政幸

   

  本研究により得られた成果を以下にまとめる。 1)Bi2212の一粒子スペクトルにおける低温(T<)とほぼ一致することが明らかとなった。さらに、T_c(p),T^*(p)の値は系によって異なるが、多くの高温超伝導体においてpを最大のT_c(T^_cを与えるホール濃度p_0で、T_c(p),T^*(p)をT^_cで規格化すると、T_cとT^*およびT_(∝2Δ_0)はそれぞれユニバーサルな曲線にほぼ載ることも明らかになった。このことは、高温超伝導体の擬ギャップと超伝導が一体の現象であることを示しており、超伝導転移の機構を考える上で重要な成果である。 2)STSにより、La214における擬ギャップの存在が始めて明らかとなった。また、電子比熱や磁化率の測定から、T^*はLa214でもBi2212と同様T_とほぼ一致することが明らかになった。 3)La214における磁化率の磁場依存性と電子比熱の温度変化の測定から、超伝導臨界揺らぎはT_c近傍のT^*よりかなり低温(T_cの2割程度高温)で発達し始めることが明らかになった。擬ギャップの起源として一重項(電子)対の形成が考えちれているが、本研究における超伝導臨界揺らぎに関する結果は、T^*付近から形成されると思われる一重項対の集団運動におけるコヒーレンスがT^*より十分低温のT_cの近傍で発達することを示しており、超伝導転移の機構を考える上で興味深い成果である。 4)Bi2212とLa214両系で、k_BT_c〜pΔ_0の関係が成立すること、すなわち、T_cを決めるエネルギー・スケールが〜pΔ_0となることが明らかにされた。 本研究では、以上の研究成果を基に超伝導転移の機構も考案された。
• Li誘起による半導体ZnOの強誘電性発現と電子材料の可能性

  日本学術振興会：科学研究費助成事業

  研究期間 : 1997年04月 -1998年03月 

  代表者 : 小野寺 彰, 小田 研

   

  II-VI族半導体ZnOのZnをLiで一部置換すると強誘電性を示すことを発見し、そのメカニズムの解明を試みた。ZnOは電子系が主因の新しいタイプの強誘電性である可能性が大きい。この系が強誘電性研究に適しているのは、構造が簡単であること、Li添加により抵抗が急激に増加し、高抵抗になる点にある。次ぎのような、基本的な誘電特性、小さい格子系の変化を明らかにした。 (1) Znを3d電子を持たないLiで世換すると、強誘電性が誘起される。 (2) SPS法で作製したセラミックスでは、転移点が470Kまで上昇した。Tc-χ相図を得た。 (3) ZnO単結晶Li雰囲気中で処理した場谷、セラミックスと同様な異常がみられる。 (4) ZnOは相転移に伴う構造変化が小さく、空間群も変化しない。 (5) 電子系のわずかな変化が相転移を誘起しうることを現象論的に示した。 酸化亜鉛は機能性酸化物として、最近広く注目を浴びている。半導体材料との整合性も良いことから、デバイスに組み込む強誘電体薄膜材料としても展開が期待される。また、In,Alドープにより高伝導度の透明電極材料になること、青色レーザーが発振可能なこと等の興味ある特性を示す。光ICなどの発光部、機能部、電極部などが一つの基礎材料で構成可能となる。また、p型のドーピングに成功すれば、透明太陽電池が可能になる。ガラス窓で被われたオフィスビルの電力源にもなりうるなど可能性にみちた次世代の夢の電子材料である。
• 高圧下におけるランタン銅酸化物の逐次構造相転移と超伝導異常

  日本学術振興会：科学研究費助成事業

  研究期間 : 1995年04月 -1997年03月 

  代表者 : 伊土 政幸, 小田 研

   

  La_<2-X>M_XCuO_4(M=Ba,Sr)系銅酸化物超伝導体では、x=1/8の近傍で超伝導が著しく抑制されることが知られている。最近、Ndを添加したLa_<2-X>Sr_XCuO_4(La-Nd-Sr)系の中性子散乱実験から、超伝導の抑制原因は電荷(ホール)とスピンのストライプ相関の発達にあることが指摘された。そして、低温(T_1〜60K)で低温正方晶(LTT)あるいはPccn斜方晶への構造相転移が起こると、格子ポテンシャルによってドメインウオール内のホールがピン止めされ、系が絶縁体的となると考えられた。しかし、Ndを添加したLa_<2-X>Ba_XCuO_4(La-Nd-Ba)系では、Ndの添加により構造相転移温度T_1は100K以上に上昇するが、電荷とスピンのストライプ秩序の形成は60Kに止まる。このためストライプ秩序とT_1での構造相転移との関連性の有無が改めて問題となった。そこで、本研究では、両者の関連性を明らかにするため、圧力の印加によりT_1での構造相転移を抑制すると電荷(ホール)とスピンのストライプ秩序にどの様な影響が現れるかを調べた。その結果、 1)La系では結晶構造にかかわらず電荷とスピンのストライプ相関がT^*〜60K付近で発達すること。T^*〜60Kでの結晶構造がLTT(あるいはPccn斜方晶)であれば、結晶ポテンシャルが電荷(ホール)のピン止めを通じてストライプ秩序の安定化をもたらすこと。更に、x=1/8の試料では整合うエネルギーもピン止めに寄与すること等が確認できた。 2)また、Ndを添加した試料では、Ndサイト上の局在磁気モーメントによるランダムポテンシヤルのためストライプ相関の発達が乱されることが分かった。
• 走査トンネル顕微鏡による高温超伝導体の電子対の対称性と電子対破壊の直接観察

  日本学術振興会：科学研究費助成事業

  研究期間 : 1995年04月 -1996年03月 

  代表者 : 小田 研, 桃野 直樹

   

  近年発見された銅酸化物の高温超伝導は反強磁性相に隣接して出現することから、反強磁性揺らぎと超伝導をもたらす電子対の形成機構との関連性に大変興味が持たれている。電子対の形成に反強磁性揺らぎが関与するときには、超伝導ギャップに反映される電子対波動関数の対称性は、d波のもので、フォノンを媒介とする従来型の超伝導の対称性(s波)とは異なることが示されている。したがって、銅酸化物における超伝導ギャップの対称性を明らかにすることは、その対形成の機構を解明する上で重要である。 本研究で申請者らは、Bi系銅酸化物高温超伝導体(Bi_2Sr_2CaCu_2O_<8+δ>、略称Bi2212)におけるCu-O面(高温超伝導に本質的な原子面)の鮮明な走査型トンネル顕微鏡(STM)原子像を液体ヘリウム温度の極低温下で観測し、このSTM原子像を観測する過程でトンネル分光(STS)を行うことに成功した。 以下に得られた結果を列記する。 1)Bi2212におけるトンネル・スペクトルはCu-Oの結合方向に対して45°傾いた方向にノードを持つ超伝導ギャップと合致する。 2)STM探針を試料表面に極端に接近させるこのにより、ノードで超伝導ギャップの符号が反転するd波超伝導体で期待される非磁性不純物による電子対破壊が観測された。この結果とノードの方向に関する知見を考え合わせることにより、Bi2212の超伝導ギャップの対称性はd_であることが明らかにされた。 3)電子対形成の相互作用の強さと関係する超伝導ギャップの大きさは、Cu-O面のキャリア濃度が小さくなると共に増大し、反強磁性相関の発達の程度と相関することが明らかにされた。
• 走査型トンネル分光による高温超伝導体のクーバー対の対称性に関する研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1994年04月 -1995年03月 

  代表者 : 小田 研

   

  高温超伝導を担っている電子対の対称性を明らかにすることは、その発現機構に関する直接的な知見が得られるものと注目されている。申請者らは、ビスマス系銅酸化物高温超伝導体における電子対の対称性を明らかにするために、走査トンネル顕微鏡(STM)を用いて、この系の原子像観察とトンネル分光を行った。得られた成果は以下の通りである。 (1)液体ヘリウム温度の極低温下で、高温超伝導を担っている銅-酸素面の鮮明な原子像が観測された。銅-酸素面の原子像観察に成功したのは、これが世界的に見ても最初の例である。また、この原子像の特徴から、超伝導を担っているキャリヤ-が銅原子の3d軌道と酸素原子の2p軌道に主に存在することが明らかになった。このことは、高温超伝導体の電子状態に関する重要な知見である。 (2)銅-酸素面の鮮明なSTM像観察と同時にトンネル分光(STS)を行い、明瞭な超伝導ギャップを観測した。銅-酸素面の鮮明なSTM像と超伝導ギャップの同時観測は申請者らが最初である。STSの実験にとって、鮮明なSTM像が観測されるときが、最も理想的で、信頼性の高いデータが得られる。したがって、申請者らの結果は、電子対の対称性に関する議論にとって極めて重要な成果と言える。 (3)銅-酸素面の鮮明なSTM像と同時に測定されたトンネルスペクトルから、ビスマス系銅酸化物における電子対の対称性はd波的であることが示された。このことは、超伝導を担っている電子対の形成には、異方的な引力機構が関与していることを意味するもので、超伝導の発現機構を考える上で極めて重要な結果である。
• ランタン銅酸化物の正方晶相と超伝導に関する研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1993年04月 -1994年03月 

  代表者 : 伊土 政幸, 小田 研

   

  本研究では、La_<2-x>Sr_xCuO_4系の(高温)正方晶相(p>0.2)の超伝導特性を明らかにするため、T0.2)は、高圧下における正方晶相と同様に、バルク超伝導を示すことが結論された。しかし、xが0.2を越える領域では超伝導がギャップレスとなるため電子比熱係数γはT<
• 走査型トンネル分光による銅酸化物高温超伝導体の電子対形成機構の研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1993年04月 -1994年03月 

  代表者 : 小田 研, 伊土 政幸

   

  銅酸化物高温超伝導体の電子対形成機構を明らかにする上で、現在、電子対の対称性を調べることが急務となっている。申請者らは、銅酸化物高温超伝導体における電子対の対称性に関する知見を得ることを目的として、極低温用走査型トンネル顕微鏡(STM)を用いてビスマス系銅酸化物高温超伝導体のトンネル分光(STS)を液体ヘリウム温度で行った。 購入されたターボ分子ポンプによりSTM/STSの実験に不可欠な清浄な試料表面が得られるようになり、以下のような成果が得られた。ビスマス系銅酸化物高温超伝導体の試料表面に存在するBi-O面の半導体ギャップよりも大きなバイアス電圧でSTM観察を行うことによってBi-O面の原子像が観測され、一方、小さなバイアス電圧ではBi-O面の内側に存在するCu-O面の原子像が観測された。低温で銅酸化物高温超伝導体の原子像が観測された例は非常に少なく、本研究はその数少ない成功例の一つである。しかも、超伝導の発現に本質的なCu-O面の原子像を観測したのは世界的に見ても申請者らが最初と思われる。さらに、Cu-O面の特定の原子サイトにおけるSTSを超伝導を示す低温で行うことにより、銅酸化物高温超伝導体の電子対の対称性がd波的である可能性で示唆する結果が得られた。この結果は銅酸化物高温超伝導体における電子対の形成機構を解明する上での重要な手掛かりとなる。
• ランタン銅酸化物の高ホール濃度領域における超伝導特性の解明

  日本学術振興会：科学研究費助成事業

  研究期間 : 1992年04月 -1993年03月 

  代表者 : 伊土 政幸, 小田 研

   

  La-Sr系は、ホール濃度Pを絶縁体から超伝導の消失する領域まで系統的に変える事の出来る唯一の系である。この系ではPが0.2を越える辺りから、系の伝導性が良くなるにもかかわらずTcが急速に低下する。このため、超伝導の発現機構を考える上で高ホール濃度領域における超伝導特性を明らかにすることが重要となっている。ところで、La-Sr系ではp〜0.2になると斜方晶相に代わって正方晶相が低温まで安定化するが、これに伴って超伝導が消失するとの主張があり長い間論争となっていた。 本研究では、まず、"La-Sr系の正方晶相はバルク的超伝導を示すか否か"を明らかにするため、Sr濃度が0.2以下の試料に高圧を加えて(高温の)正方晶相を低温まで安定化し、その超伝導特性を反磁性から調べた。このような高圧実験ではx<0.2の良質試料を用いるため、(高温)正方晶相の超伝導特性を正確に調べることが期待できる。 次に、超伝導相と常伝導相における電子比熱係数γの差から高濃度領域(P>0.2)の超伝導体積百分率を見積ることを行った。常伝導状態のγは、Cuサイトに小量の不純物(Zn)を添加して超伝導を抑制することで測定した。 これらの結果、La-Sr系の正方晶相はパルクの超伝導を示すことが結論できた。しかし、高濃度領域(P>0.2)では超伝導相の充分低温でもγが有限となり、その値はxの増加と共に大きくなる。一方、磁化率の測定からホール濃度Pが0.19を越えた辺りから局在スピンが現れ、Tcが大きく低下することが明らかとなった。この局在スピン数はxと共に増加することから、これらの局在スピンが対破壊を引き起こすため超伝導がギャップレスとなってγが低温(T≪Tc)でも有限の値になることが結論できた。
• 高圧を用いたランタン銅酸化物系の超伝導と逐次構造相転移に関する研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1990年04月 -1993年03月 

  代表者 : 伊土 政幸, 小田 研

   

  本研究はLa_<2-x>M_xCuO_4(M=Ba,Sr)系における超伝導と正方晶-針方晶転移および斜方晶-低温斜方晶転移との関連性を明らかにすることを目的としている。これまでに、La-Ba(M=Ba)系における後者の構造相転移に伴ってフェルミ準位での状態密度N(O)が減少するため、超伝導転移温度Tcが大きく低下することを明かにしてきた。本研究では、始めに低温X線回折実験から、N(O)の減少は構造相転移によりCu-O面内の酸素が二つの非等価なサイトに分かれることに関係することを指摘した。その後、熱膨張率の測定から高圧下での構造相転移の様子を詳細に調べ、x=0.125のごく近傍を除き、構造相転移と超伝導が競合していることを確認した。一方、x=0.125の試料では2GPaの高圧によって構造相転移を完全に抑制しても、Tcは10K程度までしか回復しないことが明らかとなった。このことは、x〜0.125の試料では構造相転移以外にも超伝導を抑制する機構が存在することを意味する。そこで、高圧下での電気抵抗の温度依存性を詳しく測定したところ、x=0.125の試料に限って電子系に強い散乱が働いていることが分かった。その具体的散乱機構を明かにすることが今後の課題となっている。 一方、La-Sr系の正方晶-斜方晶転移を熱膨張率から調べた結果、ある臨界圧力Pc以上で正方晶相が低温まで安定化することが分かった。この高圧下の正方晶相でもバルクの超伝導が見られること、また、常圧の正方晶相(x>0.2)の超伝導はギャップレスとなっているがバルク的であることを確認した。さらに、高圧下でのTcの圧力依存性を精密に測定し、Pc以下の圧力下では構造相転移温度が減少するにしたがってTcは増加するが、斜方晶相が消失し正方晶相となると(P≧Pc)その圧力係数が非常に小さくなることを見つけた。この結果から、斜方晶相では酸素八面体が傾くことによって超伝導が抑制されることを始めて明らかにした。

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