2023 Fiscal Year Final Research Report
Novel multi-fluctuation theory by a multi-orbital higher-order many-body effect
| Project/Area Number |
17K05543
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Condensed matter physics II
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| Research Institution | Nagoya University (2018-2023)
Okayama University (2017) |
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Principal Investigator |
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| Project Period (FY) |
2017-04-01 – 2024-03-31
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| Keywords | 強相関電子系 / 鉄系超伝導体 / ツイスト2層グラフェン / Ni酸化物 / ネマティック秩序 / 軌道秩序 |
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| Outline of Final Research Achievements |
1. Clarification of the diverse nematic order in iron-based superconductors: the 45°rotated nematic order in highly hole-doped systems and the hidden nematic order in BaFe2As2 and NaFeAs above the structural transition temperature were understood in a unified manner by solving the DW equation, which incorporates higher-order many-body effects.
2. Nematic order in magic-angle twisted bilayer graphene (MATBG): In MATBG, SU(4) symmetry exists in the local Coulomb interaction due to the composite spin and valley degrees of freedom. It is shown that the SU(4)-fluctuation interference causes the nematic bond order.
In summary, it is shown that the novel order is explained by the multi-orbital higher-order many-body effect.
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| Free Research Field |
強相関電子系の超伝導・輸送現象
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| Academic Significance and Societal Importance of the Research Achievements |
鉄系超伝導体や魔法角ツイスト2層グラフェンに代表される多軌道強相関電子系においては、超伝導相、ネマティック秩序等多彩な相図が出現する。本研究成果により、多軌道系の高次多体効果をミクロから取り扱うことで、物質依存性まで含めて統一的に相図を理解することが出来ることが示された。つまり、本研究で取り扱った高次多体効果は、強相関電子系全体の理解に繋がることが示唆される。強相関電子系は新規機能物質の宝庫であるため、強相関電子系の理解は社会の発展に寄与すると期待している。
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