Asano Yasuhiro

Faculty of Engineering　Applied Physics　Quantum Matter PhysicsProfessor
Last Updated :2026/03/05

■Researcher basic information

Degree

  • Mar. 1995

Researchmap personal page

Home Page URL

Researcher ID

  • B-4582-2010

J-Global ID

Research Keyword

  • 超伝導
  • メゾスコピック物理
  • 物性理論
  • スピン三重項超伝導
  • 奇周波数超伝導
  • ジョセフソン接合
  • トポロジカル物質

Research Field

  • Natural sciences, Magnetism, superconductivity, and strongly correlated systems

Educational Organization

■Career

Career

  • Apr. 2024 - Present
    北海道大学 工学(系)研究科(研究院), 教授

Educational Background

  • Apr. 1992 - Mar. 1995, Nagoya University, 大学院工学研究科, Department of Applied Physics

■Research activity information

Papers

Other Activities and Achievements

Books and other publications

  • Andreev Reflection in Superconducting Junctions　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Springer, Nov. 2021, [Single work]
  • Fundamentals and Frontiers of the Josephson Effect　　　　　　　　　　　　　　　
    Yasuhiro Asano, Yukio Tanaka, Sec. 4 Charge Transport in Unconventional Superconductor Junctions
    Springer, Aug. 2019, 9783030207267, English, Textbook, [Contributor]

Lectures, oral presentations, etc.

  • Anomalous proximity effect due to odd-frequency Cooper pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Workshop on Mesoscopic Superconductivity and Quantum Transport, 13 Oct. 2023, English, Invited oral presentation
    13 Oct. 2023 - 13 Oct. 2023, [Invited]
  • Josephson Effect of two-band/orbital superconductors　　　　　　　　　　　　　　　
    Y. Asano
    Topological Superconductivity in Quantum Materials, 19 Oct. 2020, English, Invited oral presentation
    19 Oct. 2020 - 22 Oct. 2020, [Invited]
  • Nonlocal conductance due to a chiral edge mode　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Oxide Superspin Workshop 2019, 25 Jul. 2019, English, Invited oral presentation
    24 Jul. 2019 - 28 Jul. 2019, [Invited]
  • Flat-band Andreev bound states and odd-frequency Cooper pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Majorana Fermions and topological Material Science, 26 Jul. 2018, English, Invited oral presentation
    Ettore Majorana Foundation and Centre for Scientific Culture,\\ Erice, Sicily, Italy, [Invited], [International presentation]
  • Dirty two-band superconductivity　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Oxide Superconducting spintronics 2017, 26 Nov. 2017, English, Invited oral presentation
    Yukawa Institute for Theoretical Physics, Kyoto Univ., Japan, [Invited], [International presentation]
  • Flat-band Andreev bound states and odd-frequency Cooper pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Novel Quantum States in Condensed Matter 2017, 16 Nov. 2017, English, Invited oral presentation
    Yukawa Institute for Theoretical Physics, Kyoto Univ., Japan, [Invited], [International presentation]
  • Dirty two-band superconductivity　　　　　　　　　　　　　　　
    Yasuhiro Asano
    The 6th International Conference on Mesoscopic Structures: Fundamentals and Applications, 09 Jul. 2017, English, Invited oral presentation
    Hotel “Baikal”, Listvyanka, Irkutsk region, Russia, [Invited], [International presentation]
  • Anomalous magnetic response and electric transport due to odd-frequency Cooper pair　　　　　　　　　　　　　　　
    Yasuhiro Asano
    International Conference on Superconducting hybrid nanostructures: physics and application, 23 Sep. 2016, English, Invited oral presentation
    Moscow Institute of Physics and Technology, Dolgoprudny, Russia,, [Invited], [International presentation]
  • Edge current in a small chiral superconductor　　　　　　　　　　　　　　　
    Yasuhiro Asano
    SPIE. photonics and spintronics 2016, 01 Sep. 2016, English, Invited oral presentation
    San Diego Convention center, San Diego, U. S. A., [Invited], [International presentation]
  • Paramagnetic response of small topological superconductors　　　　　　　　　　　　　　　
    Yasuhiro Asano
    International Conference on Interaction of Superconductivity and Magnetism in Nanosystems, 04 Sep. 2015, English, Keynote oral presentation
    Moscow State Institute of Steel and Alloys, Moscow, Russia, [Invited], [International presentation]
  • Anomalous proximity effect and more than one Majorana fermion　　　　　　　　　　　　　　　
    Yasuhiro Asano
    11th International Workshop on Nanomagnetism \& Superconductivity at the Nanoscale, 01 Jul. 2015, English, Invited oral presentation
    Nuva Hotel Comarruga, Coma-Ruga, Spain, [Invited], [International presentation]
  • Anomalous proximity effect and more than one Majorana fermio　　　　　　　　　　　　　　　
    Yasuhiro Asano
    11th International Conference on Ceramic Materials Components for Energy and Environmental Applications, 16 Jun. 2015, English, Invited oral presentation
    Hotel Hyatt Regency, Vancouver, Canada, [Invited], [International presentation]
  • Magnetic property of Odd-frequency Cooper Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    International Conference on Topological Quantum Phenomena, 17 Dec. 2014, English, Invited oral presentation
    Kyoto University, Kyoto, Japan,, [Invited], [International presentation]
  • Properties of Odd-frequency Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    日本物理学会秋の分科会, 領域6シンポジウム, 07 Sep. 2014, English, Invited oral presentation
    中部大学, 春日井, [Invited], [Domestic Conference]
  • Paramagnetic Meisner Effect in Small Unconventional Superconductors　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Physics and Applications of Superconducting Hybrid Nano-Engineered Devices, 01 Sep. 2014, English, Invited oral presentation
    Grand Hotel Santamaria, Santa Maria di Castellabate, Italy, [Invited], [International presentation]
  • Paramagnetic Meisner Effect in Small Unconventional Superconductors　　　　　　　　　　　　　　　
    Yasuhiro Asano
    10th International Workshop on Nanomagnetism \& Superconductivity at the Nanoscale, 02 Jul. 2014, English, Invited oral presentation
    Hotel Vita Comarruga, Coma-Ruga, Spain, [Invited], [International presentation]
  • Three-dimensional Symmetry Breaking Topological States　　　　　　　　　　　　　　　
    Yasuhiro Asano
    MTI and ITS Fall Workshop 2013: Coherent Hybrid Structures on the Mesoscale, 16 Oct. 2013, English, Invited oral presentation
    Hilton hotel Orrington/Evanston, Illinois, U. S. A., [Invited], [International presentation]
  • Surface/interfacial states of topological materials　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Electron Correlation in nanostructures 2013, 03 Oct. 2013, English, Invited oral presentation
    Hotel Yalta-Intourist, Yalta, Ukraine, [Invited], [International presentation]
  • Majorana fermions and Odd-frequency Cooper Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    MTI Nonconventional Insulators Workshop 2012, 13 Nov. 2012, English, Invited oral presentation
    Argonne National Laboratory, Illinois, U. S. A., [Invited], [International presentation]
  • Majorana fermions and Odd-frequency Cooper Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    9th International Conference on New Theories, Discoveries and Applications of Superconductors and Related Materials, 17 Sep. 2012
    Grand Hotel Villa Tuscolana, Roma, Italy
  • Majorana fermions and Odd-frequency Cooper Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Workshop on Superconducting Nanohybrids 2012, 05 Sep. 2012, English, Invited oral presentation
    Donostia International Physics Center, San Sebastian, Spain, [Invited], [International presentation]
  • Odd-frequency Cooper Pairs in spin-triplet superconducting junctions　　　　　　　　　　　　　　　
    Yasuhiro Asano
    The International conference "Dubna-Nano2012, 13 Jul. 2012, English, Keynote oral presentation
    Bogoliubov Laboratory of Theoretical Physics, Dubna, Russia, [Invited], [International presentation]
  • Odd-frequency Cooper Pairs in ferromagnetic junctions　　　　　　　　　　　　　　　
    Yasuhiro Asano
    8th International Workshop on Nanomagnetism & Superconductivity, 05 Jul. 2012, English, Invited oral presentation
    Hotel Marvel, Coma-ruga, Spain,, [Invited], [International presentation]
  • Proximity Effect of Odd-frequency Cooper Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    International Conference on Topological Phenomena, TQP2012, 19 May 2012, English, Invited oral presentation
    Nagoya University, Japan, [Invited], [International presentation]
  • Odd-frequency Cooper Pairs and Their Effects on Surface Impedance　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Superconductivity and Magnetism, SM-2011, 07 Oct. 2011, English, Invited oral presentation
    Kishinev, Moldva, [Invited], [International presentation]
  • Anomalous Surface Impedance due to Odd-frequency Cooper Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    7th International Workshop on Nanomagnetism \& Superconductivity, 05 Jul. 2011, English, Invited oral presentation
    Hotel Marvel, Coma-ruga, Spain, [Invited], [International presentation]
  • Anomalous Surface Impedance due to Odd-frequency Cooper Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    8th International Conference on New Theories, Discoveries and Applications of Superconductors and Related Materials, 09 Jun. 2011, English, Invited oral presentation
    J. W. Marriott Hotel Chongqing, China, [Invited], [International presentation]
  • Tunneling between Two Helical superconductors via Majorana Edge Channels　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Superconductivity and Magnetism 2010, 07 Sep. 2010, English, Invited oral presentation
    Savoy Hotel, Paestum, Italy, [Invited], [International presentation]
  • Unusual Cooper Pairs in Superconducting Proximity Structures　　　　　　　　　　　　　　　
    Yasuhiro Asano
    International Conference on Superconductivity and Magnetism 2010, 26 Apr. 2010, English, Invited oral presentation
    Porto Bello Hotel, Antalya, Turkey, [Invited], [International presentation]
  • Proximity effect in spin-triplet superconducting junctions　　　　　　　　　　　　　　　
    Yasuhiro Asano
    nternational Symposium on Novel Spin Pairing 2009, 14 Sep. 2009, English, Invited oral presentation
    Yukawa Memorial Hall, Kyoto University, Japan, [Invited], [International presentation]
  • Josephson current through a strong ferromagnet　　　　　　　　　　　　　　　
    Yasuhiro Asano
    International symposium on new directions of superconducting nanostructures 2009, 05 Sep. 2009, English, Invited oral presentation
    Nagoya University, Japan, [International presentation]
  • Luminescence of a superconducting pn Junction　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Nanoscience and Engineering in Superconductivity, Hybrid and Josephson Structures, 03 Jun. 2009, English, Invited oral presentation
    Anacapri, Italy, [International presentation]
  • "Josephson Effect in Chiral p-wave Superconductors　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Spin Helicity and Chirality in Superconductor and Semiconductor Nanostructures, 14 Jul. 2008, English, Invited oral presentation
    Karlsurhe, Germany, [Invited], [International presentation]
  • Conductance Spectroscopy of Spin-triplet Superconductors　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Probing superconductivity at the nanoscale, 05 Jun. 2008, English, Invited oral presentation
    Alicante, Spain, [Invited], [International presentation]
  • Odd-frequency Pairing State in Superconductor / Ferromagnet Junctions　　　　　　　　　　　　　　　
    Yasuhiro Asano
    日本物理学会63回年次大会, 領域3-6シンポジウム, Mar. 2008, English, Invited oral presentation
    近畿大学, 大阪, [Invited], [Domestic Conference]
  • Conductance Spectroscopy of Spin-triplet Superconductors　　　　　　　　　　　　　　　
    Yasuhiro Asano
    MTI International Argonne Fall Workshop on Nanophysics VII, 2007, Dec. 2007, English, Invited oral presentation
    National Center for Theoretical Sciences, Hsinchu, Taiwan, [Invited], [International presentation]
  • Odd-frequency Cooper Pairs in Ferromagnet/Superconductor Junctions　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Nanoscale Superconductors and their Applications, Nov. 2007, Japanese, Invited oral presentation
    Institute for Material Research in Tohoku Univ., Sendai, Japan, [Invited], [Domestic Conference]
  • Josephson Current through a Strong Ferromagnet and Odd-frequency Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Physics of Nanoscale Superconducting Heterostructures, Jul. 2007, English, Invited oral presentation
    Lorentz Center in Leiden Univ., Leiden, The Netherlands,, [Invited], [International presentation]
  • Proximity Effect in Half metals and Odd-frequency Cooper Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    International Conference on Nanoscale Magnetism, Jun. 2007, English, Invited oral presentation
    Istanbul, Turkey, [Invited], [International presentation]
  • Anomalous Josephson Effect in Unconventional Superconductor Junctions　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Quantum Phenomena in Low-dimensional Systems, Jan. 2007, English, Invited oral presentation
    [Invited], [International presentation]
  • Anomalous Proximity Effect due to Odd-Frequency Cooper Pairs　　　　　　　　　　　　　　　
    Yasuhiro Asano
    Sixth International Conference on New Theories, Discoveries and Applications of Superconductors and Related Materials, Jan. 2007, English, Invited oral presentation
    Sydney, Austraria,, [Invited], [International presentation]
  • Josephson Current through a Diffusive Half Metal　　　　　　　　　　　　　　　
    Yasuhiro Asano
    19th International Symposium on Superconductivity, Oct. 2006, English, Invited oral presentation
    Nagoya, Japan, [Invited], [International presentation]
  • Spin Current in Triplet Superconducting Rings　　　　　　　　　　　　　　　
    Yasuhiro Asano
    International Conference on Nanoscale Magnetism, Jul. 2005, English, Invited oral presentation
    [Invited], [International presentation]
  • Impurity Effect of Unconventional Superconducting Junctions　　　　　　　　　　　　　　　
    Yasuhiro Asano
    International Workshop on Physics of Superconducting pi-Phase Shift Devices, Apr. 2005, English, Invited oral presentation
    [Invited], [International presentation]
  • 異方的超伝導体接合の不純物効果　　　　　　　　　　　　　　　
    浅野泰寛
    日本物理学会秋の分科会, 領域4シンポジウム, Sep. 2004, English, Invited oral presentation
    [Invited], [Domestic Conference]
  • 超伝導ジョセフソン接合系の理論の最近の進展　　　　　　　　　　　　　　　
    浅野泰寛
    日本物理学会秋の分科会, Sep. 2002, Japanese, Invited oral presentation
    [Invited], [Domestic Conference]
  • Symmetry of Pair Potential and Josephson Effect in Dirty SNS Junctions}　　　　　　　　　　　　　　　
    Yasuhiro Asano
    The International Symposium on Superconducting Device Physics, 15 Jun. 2001, English, Invited oral presentation
    [Invited], [International presentation]

Affiliated academic society

  • THE PHYSICAL SOCIETY OF JAPAN　　　　　　　　　　　　　　　

Research Themes

  • 多自由度を持つ電子系の超伝導体における奇周波数電子対の物理
    文部省科学研究費補助金(基盤研究(B))
    Apr. 2020 - Mar. 2023
    浅野泰寛、田仲由喜夫、水島健
    日本学術振興会, 基盤研究（B)（一般）, 北海道大学, Principal investigator
  • 強相関物質のトポロジカル相　　　　　　　　　　　　　　　
    科学研究費補助金（新学術領域研究）
    2015 - 2019
    川上則雄
    文部科学省, Coinvestigator, Competitive research funding
  • Theory of spin and heat transport in topological insulator/superconductor junctions
    Grants-in-Aid for Scientific Research
    01 Apr. 2015 - 31 Mar. 2018
    KAWABATA SHIRO, TOMINAGA JYUNJI
    We have investigated the thermal and quantum transport in superconductor/topological meterial hybrid systems theoretically and numerically. Due to the suppression of the Andreev reflection by the topological spin-momentum locking induced by the spin-orbit interaction, the cooling power of the system is found to be higher than that for conventional coolers. Therefore we can extract large amount of heat from normal metals. We also have investigated the electron transport in superconducting single-electron devices and found that the heating by thermal quasiparticles gives large influences on electron transport. In addition, we have theoretically investigated several properties of chiral topological superconductors, Josephson effect through anomalous hall insulator, and impurity effect in carrier doped topological insulators.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), National Institute of Advanced Industrial Science and Technology, 15H03525
  • Topological Quantum Phenomena in Condensed Matter with Broken Symmetries (Administration)
    Grants-in-Aid for Scientific Research
    01 Apr. 2010 - 31 Mar. 2016
    MAENO Yoshiteru, TANAKA Yukio, ISHIKAWA Osamu, ZHENG Guo-qing, KASHIWAYA Satoshi, ASANO Yasuhiro, NOMURA Ryuji, ANDO Yoichi, SATO Masatoshi, UEDA Masahito
    平成27年度は研究成果とりまとめにあたり、主に次の二点を行った。


    第一に、領域活動によるこれまでの研究成果を事後評価報告書にまとめ上げ、文科省でのヒアリングを経て事後評価を受けた。結果は評価A+をいただいた。総合所見において、「本研究領域は世界をリードする多くの研究成果を生み出し、当該学問分野における我が国の国際的優位性の確保と、その向上に大きく貢献した。また、積極的にアウトリーチ活動が実施されたことは、物性物理学における新しい概念の普及という点で高く評価できる。本研究領域の活動によって、多くの若手研究者が育成されたと認められる。」との評価をいただいた。報告書作成に際しては、領域メンバーからの成果情報を収集・集積して、発表論文、招待講演、受賞などに含まれる研究成果内容の分析を加えたうえで、今後の展望も含めた。また、新学術プロジェクトならではの、異なる専門分野研究者間の連携による研究成果・論文成果、5回開催(そのうち2回は国際会議として開催)した領域研究会の成果、17回開催した「集中連携研究会」の成果、若手育成のための若手国際会議や若手相互滞在プログラムの成果、市民講座や出前講義の成果の分析も行った。


    第二に、本領域の研究活動から生み出されたトポロジカル量子現象に関する新学術領域をさらに発展させるための活動を行った。まず、引き続き領域のHP と事務局を維持し、研究成果情報の収集と公開に務めるとともに、トポロジカル量子現象の研究に関わる研究者に対しての情報ソース・フォーラムとしての機能も果たし続けた。幸い、後継新学術領域プロジェクト「トポロジーが紡ぐトポロジカル物質科学のフロンティア」が採択されたので、さらに飛躍的な発展を生むために必要な引き継ぎ活動を行った。
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Kyoto University, 22103001
  • Paramagnetic Meissner effect in topological superconductors
    Grants-in-Aid for Scientific Research
    2014 - 2016
    ASANO Yasuhiro, AMITSUKA Hiroshi
    The diamagnetism is a essential property of all superconductors. However, the paramagnetic response has been observed in a number of small superconductors. The mechanism and basic physical picture of the paramagnetic response has been an open question. In this project, we make clear (1) odd-frequency Cooper pairs appear at a surface of a topological superconductor, (2) odd-frequency Cooper pairs are paramagnetic, (3) therefore odd-frequency Cooper pairs are responsible for the paramagnetic response of a small topological superconductor at low temperature.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, Principal investigator, Competitive research funding, 26287069
  • Novel Edge States in Superconductors with Broken Time-Reversal Symmetry
    Grants-in-Aid for Scientific Research
    2010 - 2015
    MAENO Yoshiteru, KASHIWAYA Satoshi, ASANO Yasuhiro, IRIE Hiroshi, AKAZAKI Tatsushi, TERASHIMA Takahito, YONEZAWA Shingo, ISHIDA Kenji, MAEKAWA Sadamichi, KASHIWAYA Hiromi, MURAKI Koji
    To clarify the topological quantum phenomena, especially novel surface/interface phenomena, in superconductors with broken time-reversal symmetry, we investigated ruthenate superconductor Sr2RuO4 and its eutectic, as well as hybrid systems consisting of a conventional superconductor and a ferromagnet.
    We discovered the half-quantum flux state in micro-rings of Sr2RuO4, and in-gap density of states indicating its chiral-edge mode. We also accumulated new facts concerning its superconducting symmetry, such as reconfirming evidence for spin-triplet pairing from NMR and the first-order superconducting transition under in-plane magnetic fields. We deepened our knowledge of the odd-frequency pairing state characteristic of topological superconductivity. We developed a hybrid system of ferromagnetic thin film of SrRuO3 deposited on the Sr2RuO4 crystal surface, which is ideal for the investigation of novel proximity effects involving odd-frequency pairing.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Kyoto University, Coinvestigator, Competitive research funding, 22103002
  • Theory of theluminescence of Cooper pairs
    Grants-in-Aid for Scientific Research
    2010 - 2012
    ASANO Yasuhiro, SUEMUNE Ikuo
    We have theoretically made clear the mechanism of luminescence of Cooper pairs on the basis of the mean-field theory of superconductivity. The characteristic features of luminescence intensity observed in superconducting pn junctions have been explained by the theory. In addition, we have investigated the electromagnetic properties of Majorana fermion which is a promising candidate of quantum information
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, Principal investigator, Competitive research funding, 22540355
  • スピン3重項超流体の近接効果
    科学研究費補助金(特定領域研究)
    2008 - 2009
    浅野 泰寛
    超伝導には通常金属における超伝導(スピン1重項s波超伝導)の他に,銅酸化物高温超伝導(スピン1重項d波)に代表される異方的超伝導がある.超伝導体に普通の非超伝導金属(常伝導体)を接合したとき,超伝導を担うクーパー対が超伝導体から常伝導体へ染み出す現象は近接効果と呼ばれている.我々はこれまで異方的超伝導体の近接効果を調べ,近接効果はその母体となる超伝導の対称性に極めて敏感であるという重要な結論を得ている.異方的超伝導が非局所電流に及ぼす効果を明らかにする事で本研究の当初の目的のひとつである.特にスピン3重項超伝導体から染み出したクーパー対が奇周波数対称性を獲得することは、我々が明らかにした重要な性質である。奇周波数ペアは、超伝導体と強磁性体が接合した場合にも生み出され、その性質が大変注目されている。我々は、超伝導体に張り付けた金属薄膜における表面インピーダンスが超伝導体のスピン対称性に依存して特徴的なふるまいを示すことを明らかにした。また、強磁性絶縁体を超伝導体で挟んだSFS接合では、強磁性絶縁体の長さを1原子層ずつ変化させるごとにπ接合という特殊な状態が実現することを明らかにした。このπ状態と奇周波数ペアの関係は、今後の課題として残されている。
    文部科学省, 特定領域研究, 北海道大学, Principal investigator, Competitive research funding, 20029001
  • Proximity effect in unconventional superconductors
    Grants-in-Aid for Scientific Research(基盤研究(C))
    2007 - 2008
    Yasuhiro ASANO, 田仲 由喜夫, Yukio TANAKA
    超伝導の対称性は、金属で発現するスピン1重項対称性と、ルテニウム酸化物や重い電子系で有力とされるスピン3重項対称性に大別される。特にスピン3重項超伝導の物理はきわめて興味深く、注目を集めている。我々は、理論的な手法にのっとり超伝導近接効果を調べ、この2種類を明確に区別する新しい実験方法を提案した。
    Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 北海道大学, Principal investigator, Competitive research funding, 19540352
  • スピン3重項超伝導体におけるスピン流の理論的研究
    科学研究費補助金(特定領域研究)
    2006 - 2007
    浅野 泰寛, 市岡 優典
    本研究課題ではスピン3重項超伝導体に固有の輸送現象の解明を目指している.18年度はその中でもスピン・ジョセフソン効果の基本的な性質の解明と,観測に向けての提案を行った.超スピン流に関する研究はヘリウム3ですでに行われているが,本研究ではスピン3重項超伝導体Sr_2RuO_4を念頭に超スピン流を制御しながら流すための理論的提案を行った.超伝導体中のクーパー対はスピンの外に電荷の自由度をもち,電荷が電磁場とゲージ結合するためスピン流の制御が可能になるという結論を得た.スピン流の基礎的性質の研究とその応用研究は現在磁性体を用いた微小素子においてきわめて盛んに行われており,デバイス応用の可能性も高くなってきた.その意味で超伝導体を用いたスピン流の研究はとても時宜を得たものと考えられる.19年度はT字形状の超伝導体と常伝導体の接合の電気伝導測定から,スピン1重項超伝導体と3重項超伝導体の峻別が可能であることを示した.この目的のためには多くの実験があるが,ルテニウム酸化物をはじめとして多くの3重項超伝導体について,スピン3重項超伝導を否定する意見もないわけではない.こうした状況の下で,超伝導の対称性をはっきりと区別できる方法の提案は,この分野の発展に大きく寄与すると考えられる.
    文部科学省, 特定領域研究, 北海道大学, Principal investigator, Competitive research funding, 18043001
  • 巨大近接効果ジョセフソン素子の研究
    科学研究費助成事業
    2005 - 2006
    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。
    日本学術振興会, 萌芽研究, 北海道大学, 17654062
  • Quantum Effect and Synthesize of Topological quantum matter
    Grants-in-Aid for Scientific Research
    2003 - 2005
    TANDA Satoshi, INAGAKI Katsuhiko, UJI Sinya, HATAKENAKA Noriyuki, HAYASHI Masahiko, MATSUYAMA Toyoki
    We develop a new method to enhance two dimensionality of the system by making a thinner film using the "dechalcogenide method". The starting material is TaSe3 fibre, which is used as a template. The TaSe3 crystals are synthesized by the conventional chemical vapour transport method. The size of the TaSe3 crystals is typically 10 nm-1mm (thickness and width) and 100 nm-1 cm (length). We convert the TaSe3 crystals with nanoscale to TaSe2 ultrathin films. The TaSe3 crystals are set on a quartz plate in a sample chamber (Thermo Riko IVF298) evacuated to about 1×10^5 Torr. The sample chamber at approximately 1×10^3 Torr is filled with hydrogen gas in order to remove the oxygen gas. The TaSe3 crystals are heated rapidly from room temperature to 600K and then reacted with hydrogen gas for about 30 min. The chemical reaction is expressed as TaSe3 +H2(gas)=TaSe2+H2Se(gas). One selenium atom is removed from the TaSe3 template per unit cell (TaSe3=TaSe2+Se), resulting in the growth of a TaSe2 thin film on the surface of TaSe3 fibre. The surface TaSe3 crystal is converted into a TaSe2 monolayer near the surface during the de-chalcogenide processes These obtained crystals are suspended in isopropyl alcohol by sonic dispersion of 30 min to strip ultrathin TaSe2 film from TaSe3 surface. The size of the TaSe2 crystals is typically 10nm-10mm (width and length) and 10 nm (thickness). Submicron TaSe2 crystals are deposited on a substrate. We analyze these crystals by their transmission electron diffraction (TED) pattern. We discover a supercluster of electrons in the ultrathin TaSe2 crystals synthesized by our developed de-chalcogenide method. The supercluster has an unexpected structure containing 61 electrons denoted by 61×61, in addition to supercluster based on 7×7 clusters expected in triangle lattices. This new hierarchal structure and successive clustering cannot be explained by a conventional electron clustering mechanism assisted by background lattice distortions, i.e., charge-density-wave formation mechanism based on Fermi surface nesting. We propose an alternative possible formation mechanism based on saddle-point nesting, taking into account a trigonal symmetry as well as lattice distortion energy.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 15204029
  • A new blockade mechanism in q semiconductor quantum dot owing to nano-electro mechanical effects
    Grants-in-Aid for Scientific Research
    2003 - 2004
    NISHIGUCHI Norihiko, ASANO Yasuhiro
    A blockade phenomenon for electron transport in a freely suspended single-electron transistor 〜SET! is predicted. Voltages applied for its operation induce electromechanical forces acting on the SET, giving rise to structural deformation and collapse over a critical voltage. The electric characteristics become sensitive to charge fluctuations on the SET at the onset of the structural instability, leading to changes in the electrical characteristics that hinder electron transport through the SET around the zero-bias-voltage region.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 15510109

syllabus

  • 力学, 2024年, 学士課程, 工学部
  • 力学演習, 2024年, 学士課程, 工学部
  • 応用物理学, 2024年, 学士課程, 工学部
  • 応用物理学, 2024年, 学士課程, 工学部