2019 Fiscal Year Final Research Report
Study of universal pressure-temperature phase diagram of lambda-type organic conductors with bandwidth control
| Project/Area Number |
19K21033
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| Project/Area Number (Other) |
18H05843 (2018)
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| Research Category |
Grant-in-Aid for Research Activity Start-up
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| Allocation Type | Multi-year Fund (2019)
Single-year Grants (2018) |
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| Review Section |
0202:Condensed matter physics, plasma science, nuclear engineering, earth resources engineering, energy engineering, and related fields
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| Research Institution | Saitama University |
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Principal Investigator |
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| Project Period (FY) |
2018-08-24 – 2020-03-31
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| Keywords | 有機伝導体 / 温度圧力相図 / 反強磁性 / 超伝導 / 強相関電子系 / スピン密度波 / 核磁気共鳴 / ミュオンスピン回転法 |
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| Outline of Final Research Achievements |
In the organic superconductor λ-(BETS)2GaCl4, insulating phases with different magnetic states are realized by selectively substituting a part of the molecule, but the details are still unclear. It had been believed that a nonmagnetic insulating phase appears when a part of chlorine was replaced with bromine. In this study, we found a spin-density-wave phase adjacent to the superconducting phase by NMR and electrical resistance measurements. Meanwhile, when the donor molecule BETS is replaced with ET, an antiferromagnetic (AF) insulating phase is realized below 13K. To extend the universal phase diagram of donor molecular substitution, magnetization and muon spin rotation experiments for λ-(BETS)2GaCl4 were carried out. We discovered that this compound undergoes an AF transition at 22K, which updates the AF transition temperature among λ-type salts. These findings would facilitate the study of magnetic states in λ-type salts and deepen the understanding of electron correlations.
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| Free Research Field |
物性物理学
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| Academic Significance and Societal Importance of the Research Achievements |
超伝導の発現メカニズムを理解するためには、隣接相でどのような電子状態が実現しているかを解明することが重要である。本研究では、λ型有機超伝導体と呼ばれる、新奇超伝導物性が観測されている物質に着目した。この物質の一部を置換することで超伝導体から絶縁体へと変化させ、その時の磁性を調べた。主な研究成果として、これまで非磁性であると呼ばれていた絶縁相がスピン密度波相であることを明らかにした。さらに、λ型塩における新たな反強磁性絶縁体を発見した。これらの発見は、超伝導メカニズムの理論研究に資すると共に、λ型塩の統一相図についての研究を大きく推し進めるものである。
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