Study on ruthenate superconductors using epitaxy techniques

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H01866
• 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 (2020); The University of Tokyo (2018-2019)
• Principal Investigator: Uchida Masaki 東京工業大学, 理学院, 准教授 (50721726)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: ルテニウム酸化物 / 薄膜 / 超伝導体

Outline of Final Research Achievements

Purposes of this study are to realize ruthenium oxide superconductors by epitaxy technique and to elucidate their superconducting states using thin films and junctions. We have succeeded in growing Sr2RuO4 superconducting thin films with a transition temperature exceeding 1.2K, and have discussed possible superconducting symmetries which can be realized in two-dimensional limit by precisely measuring the upper critical magnetic field. We have also succeeded in preparing Sr2RuO4-Sr2RuO4 Josephson junctions, and have clarified that the magnetic field dependence of the Josephson critical current maintains time-reversal symmetry. Furthermore, by growing high-quality RuO2 single crystal thin films on various substrates and controlling epitaxial strain from the substrates, we have succeeded in realizing superconductivity at 1.7 K in RuO2.

Free Research Field

物性物理学

Academic Significance and Societal Importance of the Research Achievements

本成果は、転移温度が低く不純物や組成に非常に敏感な酸化物超伝導体の研究において、酸化物分子線エピタキシー技術を用いた新規超伝導体の開拓と、エピタキシャル薄膜やジョセフソン接合を利用した超伝導状態の解明が極めて有効であることを示しており、今後様々な酸化物への応用展開が期待される。