Theory of new developments in cuprate high-temperature superconductors induced by orbital degrees of freedom

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K03847
• 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: Ritsumeikan University
• Principal Investigator: Watanabe Hiroshi 立命館大学, 総合科学技術研究機構, 研究員 (50571238)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 銅酸化物高温超伝導体 / 軌道自由度 / 強相関電子系 / 変分モンテカルロ法

Outline of Final Research Achievements

Superconductivity, where electrical resistance vanishes below a certain temperature, is a widely studied central theme in condensed matter physics. Especially, the discovery of cuprate high-temperature superconductors in 1986, which possess significantly higher transition temperatures than conventional superconductors, has brought about revolutionary advancements in both fundamental and applied research. This study analyzes a theoretical model incorporating the often-overlooked orbital degrees of freedom of electrons in the mechanism of cuprate high-temperature superconductors through large-scale numerical calculations. Our findings successfully explain multiple unexplained phenomena. This achievement is expected to lead to new developments in cuprate high-temperature superconductors, as well as to further understanding of strongly correlated electron systems and to the creation of new superconducting materials.

Free Research Field

強相関電子系における超伝導

Academic Significance and Societal Importance of the Research Achievements

従来の理論では銅酸化物高温超伝導体の転移温度の物質依存性や、超伝導の周辺で観測されるストライプ状態を説明することは困難であった。本研究では電子の軌道自由度の効果を詳細に調べ、超伝導を主導する軌道と阻害する軌道を明確にすることで上記の困難を解決することに成功した。これによりさらなる転移温度の向上の指針を示すことが可能になった。また、得られた知見が有機超伝導体など他の超伝導物質の理解にもつながり、より広範な理論体系の構築に貢献できると期待される。