Simultaneous investigation of superconducting order parameter and charge excitations in cuprate superconductors via resonant inelastic x-ray scattering

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K13994
• 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: Tohoku University
• Principal Investigator: Suzuki Hakuto 東北大学, 学際科学フロンティア研究所, 助教 (80922947)
• Project Period (FY): 2022-04-01 – 2024-03-31
• Keywords: 高温超伝導 / プラズモン / 長距離クーロン相互作用

Outline of Final Research Achievements

Superconductivity is a phenomenon where the electrical resistance of a metal becomes zero at low temperatures. Since the discovery of high-temperature superconductivity in cuprates, superconductivity has been found in various transition metal compounds. Superconductivity in cuprates cannot be explained by the conventional mechanism that involve lattice vibrations as a pairing glue but is considered to involve unconventional mechanisms mediated by the oscillations of electronic charge density or magnetic moments. This study aims to elucidate the behavior of charge oscillation modes using resonant inelastic x-ray scattering. It was found that the charge oscillation modes in the group of cuprates exhibiting the highest transition temperatures can only be explained by considering long-range Coulomb interactions between electrons in different CuO2 sheets.

Free Research Field

強相関電子系

Academic Significance and Societal Importance of the Research Achievements

本研究の結果、銅酸化物において電荷密度の集団的な振動が普遍的に存在し、かつその振る舞いが超伝導の発現するCuO2層の数に強く依存することが明らかとなった。この結果は３枚のCuO2層を含む銅酸化物において超伝導転移温度が最高になる理由を解明する可能性がある。また、鉄系やニッケル酸化物における非従来型超伝導一般においても同様の電荷の振動モードの存在が期待され、広く非従来型超伝導機構における電荷自由度の重要性を示唆するものである。
本研究で確立した散乱角度を連続的に変化させる共鳴非弾性X線散乱手法は、NanoTerasuにおける超高分解能RIXS測定において幅広い量子物質に対して適用可能である。