Observation of Andreev bound states in high-Tc cuprates by photoemission microscopy

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K03749
• 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: National Institutes for Quantum Science and Technology (2020-2022); Hiroshima University (2019)
• Principal Investigator: Iwasawa Hideaki 国立研究開発法人量子科学技術研究開発機構, 関西光科学研究所 放射光科学研究センター, 上席研究員 (90514068)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 角度分解光電子分光 / 銅酸化物高温超伝導体 / アンドレーエフ束縛状態 / 光電子顕微分光 / 機械学習

Outline of Final Research Achievements

The existence of Andreev bound states on the (110) surface of cuprate high-temperature superconductors has been widely demonstrated through theoretical calculations and tunneling spectroscopy. However, there have been no reports of their observation using angle-resolved photoemission spectroscopy (ARPES), which is, in principle, capable of detecting such states. This is likely due to the difficulty of performing ARPES measurements on the (110) surface that is not easily cleavable. Therefore, in this study, we performed ARPES measurements on the (100)/(110) surfaces of cuprate high-temperature superconductors using spatially-resolved ARPES with micro-focused synchrotron radiation. Furthermore, we developed machine learning-based data analysis methods for spatially-resolved ARPES on inhomogeneous sample surfaces, leading to significantly improved efficiency in analyzing and understanding the spatial mapping ARPES data.

Free Research Field

固体物性、放射光物性

Academic Significance and Societal Importance of the Research Achievements

本研究では、顕微ARPESを活用することで、非容易へき開面でのARPES測定を確立し、銅酸化物高温超伝導体の(100)面および(110)面の電子状態の観測に成功した。また、機械学習を用いた顕微ARPESデータ解析手法を開発し、顕微ARPES計測の効率化と高速化に成功した。本研究により高度化した計測・解析技術は、界面におけるアンドレーエフ束縛状態や、局所領域において存在が予測される高次トポロジカル絶縁体などの顕微観測にも大きく貢献できると考えられるため、波及効果も大きい。