2021 Fiscal Year Final Research Report

Superconductivity in new type of noncentrosymmetric crystal structure compounds

Research Project

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Project/Area Number	19K03755
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
Research Institution	National Institute for Materials Science
Principal Investigator	ISOBE Masaaki 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, 上席研究員 (10354309)
Co-Investigator(Kenkyū-buntansha)	新井正男国立研究開発法人物質・材料研究機構, 技術開発・共用部門, ステーション長 (40222723)
Project Period (FY)	2019-04-01 – 2022-03-31
Keywords	超伝導 / 強相関電子系 / 空間反転対称性 / 電子構造
Outline of Final Research Achievements	Noncentrosymmetric superconductivity refers to the superconductivity that occurs in spatially asymmetric systems which have no inversion center in the crystal structure. It has been theoretically predicted that in such a superconducting system, odd parity component is mixed in the Cooper pair wavefunction and that the upper critical magnetic field may become huge. In order to clarify the mechanism of noncentrosymmetric superconductivity, we studied the superconducting state in the new compound BaIrSi2. As a result, it was found that BaIrSi2 is a BCS-type intermediate coupling superconductor. Furthermore, we conducted new material search based on knowledge obtained from the physical properties and electronic structure in BaIrSi2. We succeeded in discovering new type of superconductors BaRhSi2 and Li2IrSi2.
Free Research Field	超伝導、強相関電子系
Academic Significance and Societal Importance of the Research Achievements	超伝導の社会利用をより広く実現するには、転移温度（Tc）・上部臨界磁場（Hc2）・臨界電流（Jc）のブレークスルー的な改善が欠かせない。それには、既存物質の材料化の工夫だけでは限界があるため、物質固有の特性（物性）が極めて優れた物質を新たに見いだす必要がある。即ち、固体の電子論に立ち返った超伝導発現メカニズムの解明に関する研究が必要である。本研究課題では、“空間反転対称性の破れた超伝導”に着目し、その物性解明と新物質開発に取り組んだ。このような基礎研究を多く積み上げることで、将来的に、既存物質の性能を大幅に凌駕する新しい超伝導物質の発見に繋がると考える。