Elucidation of novel superconductivity induced by giant epitaxial strain

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H01804
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 29020:Thin film/surface and interfacial physical properties-related
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Uchida Masaki 東京工業大学, 理学院, 准教授 (50721726)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: ルテニウム酸化物 / 薄膜 / 超伝導体

Outline of Final Research Achievements

In this study, we have deepened research on superconductivity discovered in thin films of rutile-type oxide RuO2, aiming to elucidate the change in electronic and lattice states induced by giant epitaxial strain. After fabricating superconducting and non-superconducting thin films with the same substrate orientation and thickness, we have clarified the change in the hybridization strength between the orbital level of the Ru site and the O site by X-ray absorption spectroscopy. Specifically, it was found that the two types of Ru sites, which were originally equivalent, become inequivalent due to the giant epitaxial strain, resulting in a significant change in the orbital state near the Fermi level. Furthermore, we have developed a method of applying external strain to the thin film and clarified the change in the superconducting transition temperature of the RuO2 thin film.

Free Research Field

物性物理学

Academic Significance and Societal Importance of the Research Achievements

新しい物性を開拓していく上で、結晶の格子定数ないしボンド長を変化させる歪みは極めて重要なパラメータである。一方で、3%以上の巨大なエピタキシャル歪みを遷移金属酸化物に適用し物性開拓を進めた研究はこれまでほとんどなかった。本成果は、巨大なエピタキシャル歪みによってルチル型酸化物RuO2の電子格子状態が劇的に変化し超伝導が誘起されることを示しており、今後様々な酸化物への研究展開が期待される。