Microscopic theories on the excitonic Bose condensation and superconductivity in strongly correlated systems

2016 Fiscal Year Final Research Report

• Project/Area Number: 26400349
• 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: Chiba University
• Principal Investigator: OHTA Yukinori 千葉大学, 大学院理学研究科, 教授 (70168954)
• Co-Investigator(Renkei-kenkyūsha): YAMADA Atsushi 千葉大学, 大学院理学研究科, 准教授 (10251399) ; KONISHI Takehisa 千葉大学, 大学院融合科学研究科, 准教授 (40302525) ; SEKI Kazuhiro 理化学研究所, 柚木計算物性物理研究室, 基礎科学特別研究員 (40708533)
• Research Collaborator: KANEKO Tatsuya 理化学研究所, 柚木計算物性物理研究室, 基礎科学特別研究員 (30784433) ; SUGIMOTO Koudai 千葉大学, 先進科学センター, 特任助教 (70756072) ; NISHIMOTO Satoshi IFW-Dresden and TU-Dresden ; EJIMA Satoshi Univ. Greifswald ; FEHSKE Holger Univ. Greifswald
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 物性理論 / 強相関電子系 / 励起子凝縮 / 励起子絶縁体 / 遷移金属カルコゲナイド / コバルト酸化物 / 多極子 / 変分クラスター近似

Outline of Final Research Achievements

Renewed attention has recently been attracted to the excitonic insulator (EI) state, i.e., the state of electron-hole pair condensation in thermal equilibrium. In our research project, we have developed theoretical studies on candidate materials such as Ta2NiSe5 using the variational cluster and other approximations and obtained the results concerning: (1) the relative stability of the EI states caused by the electron-phonon and Hund's rule couplings, (2) the origin of the flat band observed in the angle-resolved photoemission spectra of Ta2NiSe5, (3) prediction of the coherence peak in the ultrasonic attenuation of Ta2NiSe5, (4) anomalous behavior of the orbital susceptibility in the EI state and Ta2NiSe5, and (5) magnetic multipole order and collective-mode excitations in a cobalt oxide material.

Free Research Field

物性物理学