Spin-polarized supercurrent induced by effective spin injection

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K14109
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Applied materials
• Research Institution: Kyushu University
• Principal Investigator: Ohnishi Kohei 九州大学, 理学研究院, 助教 (30722293)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: スピン流 / 超伝導 / トリプレットクーパー対 / スピン偏極超伝導電流 / スピントロニクス / スピン依存伝導

Outline of Final Research Achievements

In this research, a generator and a detector of spin-polarized supercurrent have been demonstrated by investiging micro-fabricated multi-layers under spin injection. (1) The spin current can be an efficient detector for the superconducting state especially at the normal metal / superconductor interface. (2) A comparison of the spin injections into Nb and NbN can be explained by a simple model of superconducting gap at the interface just below the transition temperature. (3) Several structures for spin absorption show the temperature- and structure-dependent spin signals, which indicates the spin polarized supercurrent may be detected in these structures. (4) Based on the discussion with the theoretical groups, new ways to control spin-polarized supercurrent have been provided.

Free Research Field

スピントロニクス

Academic Significance and Societal Importance of the Research Achievements

これまでスピン偏極超伝導電流の形成は、限られたトリプレット超伝導体や特定の試料構造においてのみ観測されてきた。本研究の成果により、より自由度の高い試料構造が可能となり、クーパー対の変調やスピン偏極超伝導電流の形成に関する物性値の測定が容易となった。今後、これらの研究成果を踏まえることにより、様々な方法を用いてスピン偏極超伝導電流の生成を制御可能となり、超伝導位相制御素子等を含めた新たな超伝導スピントロニクスの提案へと広がりをもつ。