| Project/Area Number |
18H01181
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Review Section |
Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
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| Research Institution | Kyoto University |
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Principal Investigator |
Fujiwara Naoki 京都大学, 人間・環境学研究科, 准教授 (60272530)
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| Co-Investigator(Kenkyū-buntansha) |
上床 美也 東京大学, 物性研究所, 教授 (40213524)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Project Status |
Completed (Fiscal Year 2020)
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| Budget Amount *help |
¥17,940,000 (Direct Cost: ¥13,800,000、Indirect Cost: ¥4,140,000)
Fiscal Year 2020: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
Fiscal Year 2019: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
Fiscal Year 2018: ¥13,260,000 (Direct Cost: ¥10,200,000、Indirect Cost: ¥3,060,000)
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| Keywords | 鉄系超伝導体 / 強相関電子系 / 核磁気共鳴 / 高圧下測定 / 量子相転移 / 量子臨界現象 / 高温超伝導 / 鉄系超伝導 |
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| Outline of Final Research Achievements |
FeSe is a unique high-Tc iron-based superconductor in which nematicity, superconductivity,and magnetism are entangled with each other in the P－T phase diagram. We performed 77Se-nuclear magnetic resonance measurements under pressures of up to 3.9 GPa on 12% S-substituted FeSe, in which the complex overlap between the nematicity and magnetism are resolved. A pressure-induced Lifshitz transition was observed at 1.0 GPa as an anomaly of the density of states and as double superconducting (SC)domes accompanied by different types of antiferromagnetic (AF) fluctuations. The low-Tc SC dome below 1 GPa is accompanied by strong AF fluctuations, whereas the high-Tc SC dome develops above 1 GPa, where AF fluctuations are fairly weak. These results suggest the importance of the dxy orbital and its intra-orbital coupling for the high-Tc superconductivity.
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| Academic Significance and Societal Importance of the Research Achievements |
鉄セレン系超伝導体は、高い超伝導転移点(Tc)をもつ鉄系超伝導体の一つであるが、Tcの起源は解明されたとは言えない。一つには、超伝導、結晶対称性の破れたネマティック秩序、磁性が複雑に関係しているためである。高いTcが４万気圧以上で実現することも問題を難しくしている。本研究では、高圧下でミクロな電子状態を調べるために、キュービックアンビル圧力セルを用いた核磁気共鳴法を開発した。この結果、ネマティック秩序と磁気揺らぎに相関があること、高いTcはネマティック秩序が消滅し、極めて弱い磁気揺らぎ下で実現することが分かった。これは、高温超伝導機構が複数の要因で決まることを示し、起源の多様性を示唆している。
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