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Monolayer Rashba superconductors studied through interaction with magnetic materials

Research Project

Project/Area Number 19H01849
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Review Section Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
Research InstitutionThe 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)

Project Period (FY) 2019-04-01 – 2023-03-31
Project Status Completed (Fiscal Year 2023)
Budget Amount *help
¥17,550,000 (Direct Cost: ¥13,500,000、Indirect Cost: ¥4,050,000)
Fiscal Year 2022: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
Fiscal Year 2021: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
Fiscal Year 2020: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000)
Fiscal Year 2019: ¥9,620,000 (Direct Cost: ¥7,400,000、Indirect Cost: ¥2,220,000)
Keywordsラシュバ効果 / 超伝導
Outline of Research at the Start

近年、我々は、鉛単原子層膜などのスピン軌道相互作用の強い金属超薄膜において、2次元面に平行にかけた磁場に対して、超伝導転移温度がPauli常磁性限界から予想されるよりも2桁小さい変化しか示さないことなどを明らかにした。本研究では、これらの系で、ラシュバ相互作用がもたらす新奇な2次元超伝導相が実現されていることを検証するために、超伝導層に非磁性の障壁層を介して磁性体層を近接させた試料を用いた実験を行い、超伝導層のスピン状態に対する直接的な知見を得る。

Outline of Final Research Achievements

The suppression rate of the superconducting transition temperature Tc of ultrathin Pb films due to magnetic adatom deposition was systematically studied for various magnetic material and coating material. All the experimental results are explained in terms of the following assumptions. (1) The suppression rate reaches its maximum when the Kondo temperature TK is about the same as Tc. (2) TK decreases rapidly as the spin of adatoms increases. (3) By inserting Au or Ag between the Pb film and the magnetic adatoms, the number of valence electrons of the host metal atoms is effectively reduced, and TK decreases significantly.
It was found that coating Pb films with Au or Ag increases the suppression rate. This seemingly surprising result can be explained in terms of (1) and (3).

Academic Significance and Societal Importance of the Research Achievements

磁性原子密度に対するTcの減少率を、磁性原子の種類を系統的に変えて測定した研究は、バルクの希薄磁性合金でも行われておらず、本研究が初めてである。また、金属表面の磁性原子のTKは、これまで走査トンネル分光法によって得られたスペクトルをファノ関数によって解析する手法によってのみ得られていたが、本研究で用いられた手法は、その検証に使えるだけでなく、走査トンネル分光法による手法が苦手とする高いTKの決定にも用いることができる。さらに、本研究でコーティングによってTKを大きく制御できることが示されたが、ナノスケールのスピントロニクス素子の開発など応用にもつながる重要な成果と確信する。

Report

(5 results)
  • 2023 Final Research Report ( PDF )
  • 2022 Annual Research Report
  • 2021 Annual Research Report
  • 2020 Annual Research Report
  • 2019 Annual Research Report
  • Research Products

    (6 results)

All 2022 2020 2019

All Journal Article (2 results) (of which Peer Reviewed: 2 results) Presentation (4 results) (of which Int'l Joint Research: 2 results,  Invited: 1 results)

  • [Journal Article] Cancellation of electron and hole contributions to the Hall effect in ultrathin Bi films grown on GaAs(110)2022

    • Author(s)
      Naoto Ito, Ryuichi Masutomi, Tohru Okamoto
    • Journal Title

      Physical Review B

      Volume: 105 Issue: 20 Pages: 205434-205434

    • DOI

      10.1103/physrevb.105.205434

    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Unconventional superconducting phases in multilayer films with layer-dependent Rashba spin-orbit interactions2020

    • Author(s)
      Ryuichi Masutomi, Tohru Okamoto, Youichi Yanase
    • Journal Title

      Phys. Rev. B

      Volume: 101 Issue: 18 Pages: 184502-184502

    • DOI

      10.1103/physrevb.101.184502

    • Related Report
      2020 Annual Research Report 2019 Annual Research Report
    • Peer Reviewed
  • [Presentation] Observation of crossover from a complex stripe phase to a helical phase in multilayer films2022

    • Author(s)
      R. Masutomi, T. Okamoto
    • Organizer
      Tsinghua Univ and The Univ of Tokyo The 7th Joint Workshop on Trans-scale Materials Science
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] GaAs劈開面上のBi薄膜の磁場中輸送特性2020

    • Author(s)
      伊藤尚人、岡本徹
    • Organizer
      第11回低温科学研究センター研究交流会
    • Related Report
      2019 Annual Research Report
  • [Presentation] Observation of crossover from a complex-stripe phase to a helical phase in multiple one-atomic-layer films2019

    • Author(s)
      R. Masutomi, T. Okamoto, Y. Yanase
    • Organizer
      Recent Progress in Graphene and two-dimensional Materials Research Conference
    • Related Report
      2019 Annual Research Report
    • Int'l Joint Research
  • [Presentation] 金属単原子層における二次元超伝導と磁性2019

    • Author(s)
      岡本徹
    • Organizer
      2019年日本表面真空学会学術講演会
    • Related Report
      2019 Annual Research Report
    • Invited

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Published: 2019-04-18   Modified: 2025-01-30  

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