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Oiwa Rikuto
| Faculty of Science Physics Electronic Condensed Matter Physics | Lecturer |
Researcher basic information
■ Degree■ URL
researchmap URLホームページURL■ Various IDs
Researcher number
- 40980917
Research KeywordResearch Field■ Educational Organization
- Bachelor's degree program, School of Science
- Master's degree program, Graduate School of Science
- Doctoral (PhD) degree program, Graduate School of Science
Research activity information
■ Awards■ Papers
- Effective Phonon Models Based on Symmetry-Adapted Multipole Basis — Hidden Chiral Phonon Angular Momentum Splitting in Ferroaxial Systems
Yu Xie; Rikuto Oiwa; Satoru Hayami
Journal of the Physical Society of Japan, 15 Aug. 2026
Scientific journal - Dual-Circular Raman Optical Activity of Axial Multipolar Order
Hikaru Watanabe; Rikuto Oiwa; Hitoshi Mori; Ryotaro Arita
Physical Review Letters, 29 Jul. 2026
Scientific journal - Theory of Many-Body Multipole Operators in Single-Centered Electron Systems: Two-Body Toroidal Monopoles in Spinless Orbitals
Shingo Kuniyoshi; Rikuto Oiwa; Satoru Hayami
Journal of the Physical Society of Japan, 15 Jul. 2026
Scientific journal - Detection of ferroic octupole ordering in d -wave altermagnetic rutile-type compounds
Masaichiro Mizumaki; Norimasa Sasabe; Takayuki Uozumi; Rikuto Oiwa; Hiroaki Kusunose
Physical Review B, 01 Jun. 2026
Scientific journal - Raman Optical Activity Induced by Ferroaxial Order in NiTiO3
Gakuto Kusuno; Takeshi Hayashida; Takayuki Nagai; Hikaru Watanabe; Rikuto Oiwa; Tsuyoshi Kimura; Takuya Satoh
Physical Review Letters, 19 May 2026
Scientific journal - Spinless electric toroidal multipoles in ferroaxial K2Zr(PO4)2 revealed by symmetry-adapted closest Wannier analysis
Yu Xie; Rikuto Oiwa; Satoru Hayami
Physical Review B, 11 May 2026
Scientific journal - Evidence for Itinerant Ferromagnetic Flat Bands Producing Large Transverse Responses
Susumu Minami; Yangming Wang; Seigo Souma; Hiroto Nakamura; Akito Sakai; Takumi Osumi; Hang Su; Hikaru Watanabe; Shun'ichiro Kurosawa; Rikuto Oiwa; Daisuke Nishio‐Hamane; Kosuke Nakayama; Takuya Nomoto; Ryotaro Arita; Takafumi Sato; Satoru Nakatsuji
Advanced Materials, Wiley, 27 Apr. 2026
Scientific journal, ABSTRACT
Interference of electronic wavefunctions may result in the emergence of a flat band, and trigger nontrivial correlated phenomena and phase formations when the flat band crosses the Fermi energy . To date, such an itinerant flat band at has been reported for electronic states without symmetry breaking. If a flat band arises at even with broken symmetry, the ordered state may offer a distinct platform for studying novel phases and spontaneous responses. Here we report experimental and theoretical evidence for itinerant ferromagnetic flat bands formed by spin‐polarized ‐electron orbitals on a stacked honeycomb–kagome lattice, hosting the alternating stack of honeycomb and kagome sublattices. Our theory together with angle‐resolved photoemission spectroscopy and magneto–thermoelectric measurements finds multiple topological flat bands at generating large Berry curvature in the ferrimagnet below its Curie temperature of 940 K. We observe large transverse responses, in particular, gigantic anomalous Nernst effect producing the largest transverse thermoelectric conductivity over 10 A at room temperature. Our study paves a path for developing itinerant magnetic flat bands and to their spintronic and thermoelectric applications. - Chirality/Axiality-Induced Axiality/Chirality via Surface Polarization
Satoru Hayami; Rikuto Oiwa; Akane Inda
Journal of the Physical Society of Japan, 15 Dec. 2025
Scientific journal - Predominant electronic order parameter for structural chirality: Role of spinless electronic toroidal multipoles in Te and Se
Rikuto Oiwa; Hiroaki Kusunose
Physical Review Research, 15 Sep. 2025
Scientific journal - Symmetry analysis of cross-circular and parallel-circular Raman optical activity
Hikaru Watanabe; Rikuto Oiwa; Gakuto Kusuno; Takuya Satoh; Ryotaro Arita
Physical Review B, 02 Sep. 2025
Scientific journal - Symmetry-adapted closest Wannier modeling based on complete multipole basis set
Rikuto Oiwa; Akane Inda; Satoru Hayami; Takuya Nomoto; Ryotaro Arita; Hiroaki Kusunose
Physical Review B, 07 Jul. 2025
Scientific journal - Spontaneous Hall effect induced by collinear antiferromagnetic order at room temperature
Rina Takagi; Ryosuke Hirakida; Yuki Settai; Rikuto Oiwa; Hirotaka Takagi; Aki Kitaori; Kensei Yamauchi; Hiroki Inoue; Jun-ichi Yamaura; Daisuke Nishio-Hamane; Shinichi Itoh; Seno Aji; Hiraku Saito; Taro Nakajima; Takuya Nomoto; Ryotaro Arita; Shinichiro Seki
Nature Materials, 24, 1, 63, 68, Springer Science and Business Media LLC, 13 Dec. 2024, [Peer-reviewed]
Scientific journal - Quantification of chirality based on electric toroidal monopole
A. Inda; R. Oiwa; S. Hayami; H. M. Yamamoto; H. Kusunose
The Journal of Chemical Physics, 160, 18, AIP Publishing, 13 May 2024, [Peer-reviewed]
Scientific journal, Chirality ubiquitously appears in nature; however, its quantification remains obscure owing to the lack of microscopic description at the quantum-mechanical level. We propose a way of evaluating chirality in terms of the electric toroidal monopole, a practical entity of time-reversal even pseudoscalar (parity-odd) objects reflecting relevant electronic wave functions. For this purpose, we analyze a twisted methane molecule at the quantum-mechanical level, showing that the electric toroidal monopoles become a quantitative indicator for chirality. In the twisted methane, we clarify that the handedness of chirality corresponds to the sign of the expectation value of the electric toroidal monopole and that the most important ingredient is the modulation of the spin-dependent imaginary hopping between the hydrogen atoms, while the relativistic spin–orbit coupling within the carbon atom is irrelevant for chirality. - Unconventional Hall effect and magnetoresistance induced by metallic ferroaxial ordering
Satoru Hayami; Rikuto Oiwa; Hiroaki Kusunose
Physical Review B, 108, 8, American Physical Society (APS), 18 Aug. 2023, [Peer-reviewed]
Scientific journal - Symmetry-adapted modeling for molecules and crystals
Hiroaki Kusunose; Rikuto Oiwa; Satoru Hayami
Physical Review B, 107, 19, American Physical Society (APS), 11 May 2023, [Peer-reviewed]
Scientific journal - Electric Ferro-Axial Moment as Nanometric Rotator and Source of Longitudinal Spin Current
Satoru Hayami; Rikuto Oiwa; Hiroaki Kusunose
Journal of the Physical Society of Japan, 91, 11, Physical Society of Japan, 15 Nov. 2022, [Peer-reviewed]
Scientific journal - Rotation, Electric-Field Responses, and Absolute Enantioselection in Chiral Crystals
Rikuto Oiwa; Hiroaki Kusunose
Physical Review Letters, 129, 11, American Physical Society (APS), 08 Sep. 2022, [Peer-reviewed], [Lead author]
Scientific journal - Analysis of model-parameter dependences on the second-order nonlinear conductivity in
Megumi Yatsushiro; Rikuto Oiwa; Hiroaki Kusunose; Satoru Hayami
Physical Review B, 105, 15, American Physical Society (APS), 28 Apr. 2022, [Peer-reviewed]
Scientific journal - Systematic Analysis Method for Nonlinear Response Tensors
Rikuto Oiwa; Hiroaki Kusunose
Journal of the Physical Society of Japan, 91, 1, Physical Society of Japan, 15 Jan. 2022, [Peer-reviewed], [Lead author]
Scientific journal - Complete Multipole Basis Set for Single-Centered Electron Systems
Hiroaki Kusunose; Rikuto Oiwa; Satoru Hayami
Journal of the Physical Society of Japan, 89, 10, 104704, 104704, Physical Society of Japan, 15 Oct. 2020, [Peer-reviewed]
Scientific journal - Spin and Orbital Susceptibilities in Hole-Doped Monolayer Superconductor MoS2 with Ising-Type Spin–Orbit Coupling
Rikuto Oiwa; Yuki Yanagi; Hiroaki Kusunose
Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019), Journal of the Physical Society of Japan, 18 Mar. 2020, [Peer-reviewed], [Lead author]
International conference proceedings - Time-reversal Symmetry Breaking Superconductivity in Hole-doped Monolayer MoS2
Rikuto Oiwa; Yuki Yanagi; Hiroaki Kusunose
Journal of the Physical Society of Japan, 88, 6, 063703, 063703, Physical Society of Japan, 15 Jun. 2019, [Peer-reviewed], [Lead author]
English, Scientific journal - Theory of superconductivity in hole-doped monolayer
Rikuto Oiwa; Yuki Yanagi; Hiroaki Kusunose
Physical Review B, 98, 6, American Physical Society (APS), 21 Aug. 2018, [Peer-reviewed], [Lead author]
English, Scientific journal
- New Systematic Analysis Method of Identifying Microscopic Essential Couplings
JPS Hot Topics, 2, 2022
We propose a systematic method of identifying essential model parameters for nonlinear response tensors. The analysis results reveal fundamental couplings in nontrivial responses and promote further development of multiferroic responses., Physical Society of Japan
- Microscopic stability mechanism of the helical structure of Tellurium
Rikuto Oiwa; Akane Inda; Satoru Hayami; Hiroaki Kusunose
New Frontiers in Advanced Magnetism 2024, 06 Aug. 2024, English, Oral presentation - Construction of symmetry-adapted Closest Wannier models using multipole basis
Rikuto Oiwa; Akane Inda; Satoru Hayami; Takuya Nomoto; Ryotaro Arita; Hiroaki Kusunose
CEMS Symposium on Emergent Quantum Materials 2024, Feb. 2024, English, Poster presentation - Construction of symmetry-adapted Closest Wannier models using multipole basis
Rikuto Oiwa; Akane Inda; Satoru Hayami; Takuya Nomoto; Ryotaro Arita; Hiroaki Kusunose
International Symposium on Quantum Electronics, Feb. 2024, English, Poster presentation - Symmetry-adapted closest Wannier tight-binding models
Rikuto Oiwa; Akane Inda; Satoru Hayami; Takuya Nomoto; Ryotaro Arita; Hiroaki Kusunose
FYR05 QLC meeting, 27 Dec. 2023, Poster presentation - Phonon-Mediated Spin-Triplet Superconductivity in Chiral Crystals
Rikuto Oiwa; Hiroaki Kusunose
Trends in the Theory of Quantum Materials - Japan-Swiss-Workshop 2022, 14 Sep. 2022, English, Oral presentation - カイラル結晶に特有な電子格子相互作用
大岩 陸人; 楠瀬 博明
日本物理学会2022年秋季大会, Sep. 2022, Oral presentation - Time-reversal symmetry breaking superconductivity in monolayer transition-metal dichalcogenides
Rikuto Oiwa; Yuki Yanagi; Hiroaki Kusunose
The 29th International Conference on Low Temperature Physics (LT29), Aug. 2022, English, Poster presentation - Microscopic origin of chirality in elemental Tellurium
Rikuto Oiwa; Hiroaki Kusunose
International Conference on Metamaterials, Photonic Crystals and Plasmonics (META 2022), Jul. 2022, English, Poster presentation - カイラル結晶における電場・回転場応答の微視的理論
大岩 陸人; 楠瀬 博明
日本物理学会2022年第77回年次大会, Mar. 2022, Oral presentation - 単体Teにおける電場誘起回転歪み
大岩 陸人; 楠瀬 博明
電流駆動現象が拓く新しい物質科学, Nov. 2021, Oral presentation - Te系カルコゲナイドの強誘電秩序下で生じる非線形応答の理論
大岩 陸人; 楠瀬 博明
日本物理学会2021年秋季大会, Sep. 2021, Oral presentation - 非線形電気伝導テンソルにおける主要モデルパラメータ抽出手法の提案
大岩 陸人; 楠瀬 博明
日本物理学会2021年第76回年次大会, Mar. 2021, Oral presentation - イジング型スピン軌道相互作用と超伝導磁化率の異方性
大岩 陸人; 柳 有起; 楠瀬 博
第19回琉球物性研究会, Nov. 2019, Oral presentation - Spin and Orbital Susceptibilities in Hole-Doped Monolayer Superconductor MoS2 with Ising-Type Spin-Orbit Coupling
Rikuto Oiwa; Yuki Yanagi; Hiroaki Kusunose
International Conference on Strongly Correlated Electron Systems 2019 (SCES2019), Sep. 2019, English, Poster presentation - 遷移金属ダイカルコゲナイドのホールドープ超伝導の性質
大岩 陸人; 柳 有起; 楠瀬 博明
日本物理学会2019年秋季大会, Sep. 2019, Oral presentation - 遷移金属ダイカルコゲナイドの時間反転の破れた超伝導
大岩 陸人; 柳 有起; 楠瀬 博明
J-Physics 地域研究会, 22 Jul. 2019, Oral presentation - Time-reversal symmetry breaking superconductivity in hole-doped monolayer MoS2
Rikuto Oiwa; Yuki Yanagi; Hiroaki Kusunose
International Conference on Frontiers of Correlated Electron Sciences (FCES19), May 2019, English, Poster presentation - 遷移金属ダイカルコゲナイドの時間反転の破れた超伝導
大岩 陸人; 柳 有起; 楠瀬 博明
日本物理学会2019年3月春季大会, 16 Mar. 2019, Oral presentation - 遷移金属ダイカルコゲナイドの多軌道超伝導の理論
大岩 陸人; 柳 有起; 楠瀬 博明
第18回琉球大学物性研究会, 24 Nov. 2018, Oral presentation - ホールドープした単層MoS2における超伝導の理論
大岩 陸人; 柳 有起; 楠瀬 博明
日本物理学会2018年9月秋季大会, 10 Sep. 2018, Oral presentation
■ Research Themes
- 軌道自由度と空間反転対称性の破れが創出する奇パリティ多極子秩序の理論
科学研究費助成事業
Apr. 2020 - Mar. 2023
大岩 陸人
本研究の目的は、電子のスピンや軌道、副格子などの複数自由度の絡み合いが創出する奇パリティ多極子秩序と交差相関物性の性質を理論的に解明することである。
本研究ではこれまでに、分子や結晶のあらゆる電子自由度を表現できる対称性適合多極子基底の生成アルゴリズムが得られている。そこで本年度は、対称性適合多極子基底を用いて第一原理電子状態計算に基づく有効模型の自動生成手法を開発した。模型ハミルトニアンは多極子基底の線形結合で表現され、各重みはモデルパラメータに対応する。第一原理計算で求まるエネルギーバンド分散を再現するように各基底の重みを最適化することで、第一原理計算に基づく有効模型を構築できる。本手法で得られる有効模型はワニエ関数を用いて求まる従来のものとは異なり、系の対称性を厳密に満たし、かつ近接サイト間の電子ホッピングのみを含むため、単位格子数個分のコンパクトな範囲に収まる。そのため、模型構築や電子格子相互作用等の計算コストの軽減が期待できる。上述のアルゴリズムをまとめた論文は投稿段階であり、計算パッケージとして公開を予定している。また、本手法の解説記事はアグネ社の固体物理誌上セミナーに掲載予定である。
さらに、本手法を用いることで固体中の隠れた多極子自由度とその演算子表現を明らかにできる。実際に本手法を用いて、カイラル物質を特徴づける微視的カイラル度の記述方法を明らかにし、その定量的評価を行った。まず、カイラル結晶の典型物質である単体Teの有効模型を生成した結果、微視的カイラル度に対応する局所的および遍歴的な電気トロイダル単極子がハミルトニアンで最も支配的な寄与であることを定量的に明らかにした。また、電気トロイダル単極子の存在下ではカイラル結晶特有の電場誘起格子回転歪みが金属・絶縁体問わず生じる可能性を示した。得られた成果はPhys.Rev.Lett.(APS)にて出版済みである。
日本学術振興会, 特別研究員奨励費, 明治大学, 20J21838
