Superconductivity and magnetism in monolayer films formed on cleaved semiconductor surfaces

2018 Fiscal Year Final Research Report

• Project/Area Number: 26287072
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: The University of Tokyo
• Principal Investigator: Okamoto Tohru 東京大学, 大学院理学系研究科(理学部), 准教授 (60245371)
• Research Collaborator: MASUTOMI Ryuichi
• Project Period (FY): 2014-04-01 – 2019-03-31
• Keywords: 表面物性 / 低温物性 / Rashba効果 / 超伝導

Outline of Final Research Achievements

It is well known that external magnetic fields and magnetic moments of impurities both suppress superconductivity. However, their combined effect on superconductivity has not been elucidated yet. We have studied the superconducting transition in ultrathin Pb films with magnetic impurities grown on a cleaved GaAs(110) surface. It was demonstrated that the transition temperature can be enhanced by external magnetic fields applied parallel to the conducting plane. Furthermore, we found that a Pb-Ce alloy, where superconductivity is totally suppressed at zero-field, actually becomes superconducting in parallel magnetic fields. These phenomena were explained in terms of the suppression of the spin-exchange scattering rate, which can be controlled by the magnetic field.

Free Research Field

低温物理学

Academic Significance and Societal Importance of the Research Achievements

これまで、磁場誘起超伝導は数例報告されているが、本研究のものは新しい機構によるものである。また、超伝導の平行磁場に対する応答を調べることにより、近藤一重項の形成の有無を明らかにできることもわかった。近年、ナノスケールのスピントロニクスデバイスへの応用の観点などからも、金属表面に吸着した磁性原子・分子と基板金属の伝導電子との間の近藤一重項の形成が大きく注目されている。下地金属として磁性体に敏感な超伝導体を用いることは、近藤一重項の形成を調べる上で非常に有効な方法であり、今後の研究の進展は応用面からも非常に重要であると思われる。