Charge-spin-orbital coupled phenomena in Slater-Mott crossover

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K14650
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: The University of Tokyo
• Principal Investigator: Suwa Hidemaro 東京大学, 大学院理学系研究科(理学部), 助教 (60735926)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 励起子絶縁体 / 励起子 / 反強磁性 / イリジウム酸化物 / スピン軌道結合 / 電子相関

Outline of Final Research Achievements

This project studied 5d-orbital electron systems characterized by charge-spin-orbital entanglement and intermediate electron-electron interaction in the Slater-Mott crossover. We revealed that triplet exciton condensation induces the antiferromagnetic order in the bilayer iridium oxide. In collaboration with experimental groups, we showed that the theory developed in this project provides a comprehensive account of experimental observations, including the significant softening of the longitudinal magnetic excitation mode near the magnetic transition temperature. Such an insulator induced by exciton condensation is called the excitonic insulator. The antiferromagnetic excitonic insulator was not identified since the theoretical prediction was made half a century ago. We found strong evidence that the bilayer iridium oxide is the first example of the antiferromagnetic excitonic insulator.

Free Research Field

物性物理　計算物理

Academic Significance and Societal Importance of the Research Achievements

長い間見つかっていなかった反強磁性型の励起子絶縁体の発見により、今後、三重項励起子の凝縮現象についてより詳細な実験的検証と操作が可能になる。本研究対象であるクロスオーバー領域は、物性物理学として興味深いだけでなく、非自明な現象が生じる温度が最大化されるため工学的応用の観点からも非常に重要である。本研究成果は、電子の電荷・スピン・軌道自由度が複雑に絡み合う物性現象の理学的解明と、将来的な量子マテリアルのデザインと工学的応用につながると期待される。