Investigation of roles of phonons and phonon-induced functional properties in strongly-correlated materials

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K14336
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics II
• Research Institution: Institute of Physical and Chemical Research (2019-2020); The University of Tokyo (2017-2018)
• Principal Investigator: Nomura Yusuke 国立研究開発法人理化学研究所, 創発物性科学研究センター, 研究員 (20793756)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 電子格子相互作用 / 機械学習 / ニッケル酸化物 / 物質デザイン / 超伝導 / 第一原理計算 / 強相関電子系

Outline of Final Research Achievements

In strongly correlated materials, which exhibit various functional properties such as magnetism and superconductivity, electronic degrees of freedom are closely intertwined with phonon (lattice vibration) degrees of freedom. However, the role of phonons in strongly correlated materials remains largely unexplored. The purpose of this study was to advance our understanding of the interplay between electron and phonon degrees of freedom in strongly correlated systems. In this study, we developed a powerful solver for electron-phonon-coupled models using machine learning, and laid the foundation for understanding the phonon degrees of freedom in real materials. In addition, we have obtained important implications showing the possibility of enhancing superconductivity by controlling the lattice structure in the recently discovered nickel oxide superconductors.

Free Research Field

物性理論

Academic Significance and Societal Importance of the Research Achievements

強相関系においてフォノンの自由度を理解することは、格子自由度を制御することによって新たな機能物性の可能性を探るための重要な知見をもたらす。これまで、フォノン自由度を解析できる強力な数値手法は限られていたが、本研究によって強力な数値手法を開発することで、フォノンの役割をより詳細に解析できるようになった。またニッケル酸化物超伝導体における物質デザインは、実験による新ニッケル酸化物合成のための有用な指針を与えた。このように理論と実験が協力することによって、新たな超伝導体を探す試みを促進することができる。