| Project/Area Number |
17K14338
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Multi-year Fund |
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| Research Field |
Condensed matter physics II
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| Research Institution | Nagoya University |
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Principal Investigator |
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| Project Period (FY) |
2017-04-01 – 2021-03-31
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| Project Status |
Completed (Fiscal Year 2020)
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| Budget Amount *help |
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2019: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2018: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2017: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000)
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| Keywords | 高温超伝導 / 強相関電子系 / 軌道秩序 / 磁気秩序 / 鉄系超伝導体 / 銅酸化物 / 超伝導 / ネマティック秩序 / ボンド秩序 / 軌道自由度 / 軌道揺らぎ / 磁気揺らぎ / 銅酸化物高温超伝導体 / 物性理論 |
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| Outline of Final Research Achievements |
In this study, we investigated the electronic states in Fe-based and cuprate superconductors based on the higher-order many-body effect described by vertex corrections. As a result, we found that the orbital fluctuations are developed in electron-doped FeSe thanks to the interference between spin fluctuations. The high-temperature superconductivity appears due to the orbital fluctuations. Also, the pressure-induced magnetic transition in FeSe is well explained based on this study. We also showed that the resonance-like structure obtained by neutron scattering measurement is consistent with the s++ wave superconductivity due to orbital-fluctuations. In addition, we proposed the bond and spin-current orders as the origins of recently discovered charge-density wave and the pseud-gap nature in cuprate superconductors.
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| Academic Significance and Societal Importance of the Research Achievements |
鉄系超伝導体をはじめとした多軌道強相関電子系では、電子の軌道・電荷・スピン自由度に起因して、様々な興味深い性質が現れる。本研究で明らかにしたバーテックス補正に起因した軌道揺らぎの発達とフルギャップs波超伝導発現の機構は、電子ドープFeSeの高温超伝導、ひいては鉄系全般の超伝導発現機構解明に貢献する結果である。また、銅酸化物高温超伝導体で新たに発見された電荷密度波、および擬ギャップ現象の起源として、バーテックス補正に起因したボンド・スピン流秩序という新機構を提唱した。鉄系および銅酸化物系超伝導体では、共にスピン・軌道・電荷の結合という共通の物理があり、強相関電子系において広く実現が期待される。
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