2020 Fiscal Year Final Research Report

Novel electronic phase in high magnetic field for highly correlated layered organic superconductors

Research Project

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Project/Area Number	17H01144
Research Category	Grant-in-Aid for Scientific Research (A)
Allocation Type	Single-year Grants
Section	一般
Research Field	Condensed matter physics II
Research Institution	National Institute for Materials Science
Principal Investigator	UJI Shinya 国立研究開発法人物質・材料研究機構, 機能性材料研究拠点, 副拠点長 (80344430)
Co-Investigator(Kenkyū-buntansha)	寺嶋太一国立研究開発法人物質・材料研究機構, 機能性材料研究拠点, 主席研究員 (40343834) 圷広樹大阪大学, 理学研究科, 准教授 (80316033)
Project Period (FY)	2017-04-01 – 2021-03-31
Keywords	強磁場電子状態 / 超伝導 / 有機伝導体 / FFLO状態
Outline of Final Research Achievements	Superconductivity is one of the most intriguing topics in solid state physics. Generally, the superconducting Cooper pairs are broken by the Zeeman effect, which gives the Pauli paramagnetic limit. However, when the superconductivity is in the clean limit and the orbital effect is strongly quenched, the Cooper pairs can survive even above the Pauli limit, which is the so-called FFLO phase. Extensive efforts have been devoted to the discovery of the FFLO phase. However, vortex phase transitions have given rise to considerable ambiguity in the interpretation of the experimental data. In this project, we have performed comprehensive magnetocaloric and torque studies of the FFLO phase transition in a highly two-dimensional organic superconductor. We have successfully observed the FFLO phase transition clearly distinct from vortex melting transitions. The phase diagram provides crucial information on the stability of the FFLO phase in magnetic fields.
Free Research Field	低温強磁場物理
Academic Significance and Societal Importance of the Research Achievements	有機超伝導体の研究は、日本が世界をリードする分野である。とくに強磁場電子状態の研究においては、申請者らのグループは最先端の研究成果を出し世界を牽引してきた。本研究成果は、長年の懸案であったFFLO相転移と磁束相転移とを明確に区別して観測することに成功したものであり、本研究分野に大きなブレークスルーをもたらした。また、高度化された測定手法や測定ノウハウは、共同研究などを通して積極的に外部にも広め、超伝導分野のみならず、関連分野の研究の発展にも貢献した。