2020 Fiscal Year Final Research Report
High-pressure reearch for magnetically mediated superconductivity in alpha-Mn
| Project/Area Number |
18K03517
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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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| Review Section |
Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
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| Research Institution | Okayama University |
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Principal Investigator |
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | マンガン / 高圧 / 異常ホール効果 / 磁性 / 超伝導探索 |
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| Outline of Final Research Achievements |
The pressure-temperature phase diagram of alpha-Mn is established. The weak ferromagnetic (WFM) phase is discovered under high pressure, where a huge anomalous Hall effect (AHE) is observed. The AHE emerging due to the change of the ordered state is the first case, indicating that the origin is the Berry curvature in the ordered state with irreducible representation same as the ferromagnet. At the critical pressure where the WFM phase disappears, the electrical resistance shows T^5/3 dependence in the wide temperature range, indicating the existence of the ferromagnetic fluctuation. The superconductivity has not been observed in the pressure range up to 17 GPa. The ferromagnetic fluctuation in the noncentrosymmetric metal causes the lack of the band degeneracy which is required in the formation of Cooper pairs.
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| Free Research Field |
物性実験
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| Academic Significance and Societal Importance of the Research Achievements |
α-Mnは単体金属であるが，高圧物性がほとんど明らかになっていない。本研究では純良単結晶の作成に成功し，その高圧物性を明らかにした。Mnは他の高温相を含め，反強磁性体として知られており，わずか1.4 GPaの圧力で弱い強磁性を示すことは驚きであった。異常ホール効果の起源については近年理解が進み，電子が感じるベリー位相と関係があることが提案されてきたが，α-Mnで発見された秩序構造の変化により現れる異常ホール効果はこれを直接的に示しており，学術的意義は大きい。ホール効果は応用にも重要であり，社会的意義も大きいと言える。期待された超伝導は観測されなかったが、その理由も明らかになった。
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