Cooperative effects of electron correlation and orbital-lattice coupling and pairing mechanism in the multi-band systems

2016 Fiscal Year Final Research Report

• Project/Area Number: 26400353
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Niigata University
• Principal Investigator: ONO Yoshiaki 新潟大学, 自然科学系, 教授 (40221832)
• Co-Investigator(Renkei-kenkyūsha): SANO Kazuhiro 三重大学, 工学部, 教授 (40201537) ; YANAGI Yuki 明治大学, 理工学部, 研究員 (70634343)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 多バンド系超伝導体 / 電子相関 / 電子格子結合 / A15型超伝導体 / Ta2NiSe5 / 軌道揺らぎ / 励起子揺らぎ

Outline of Final Research Achievements

The superconductivity in multi-band electron systems is investigated by using the theoretical approach recently developed for iron-based superconductors. On the basis of the 36-band d-p model for A15-type superconductors derived from the first-principles calculations, the effect of the intersite d-p Coulomb interaction is found to results in the orbital orders responsible for the structural transitions called the martensite transformation for both cases of V3Si and Nb3Sn, and also results in the orbital-fluctuation-mediated superconductivity with a relatively High-Tc. Transition metal chalcogenide Ta2NiSe5, a promising material for the excitonic insulator, is investigated on the basis of the quasi-one-dimensional three-chain Hubbard model and is found to show remarkable Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) excitonic orders whose fluctuation mediate FFLO superconductivity as expected to be observed in semimetallic Ta2NiSe5 under high pressure.

Free Research Field

数物系科学