Control of drastic spin-responses in strongly spin-orbit coupled systems

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H01850
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: The University of Electro-Communications
• Principal Investigator: Fuseya Yuki 電気通信大学, 大学院情報理工学研究科, 准教授 (00377954)
• Co-Investigator(Kenkyū-buntansha): 白石 誠司 京都大学, 工学研究科, 教授 (30397682) ; 徳永 将史 東京大学, 物性研究所, 准教授 (50300885)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: スピン軌道結合 / 磁気モーメント / スピンホール効果 / スピン変換 / 磁気抵抗

Outline of Final Research Achievements

(1) We clarified the spin state, which is characterized by the spin-splitting parameter Mzc, in PbTe, one of the typical materials of the strongly spin-orbit coupled systems. For the calculation, we used the "π-matrix method", a method developed by Fuseya to accurately calculated the quantized energy of electrons in a solid under a magnetic field. It has been believed that Mzc is independent of the magnetic field. However, we found for the first time that Mzc largely depends on the magnetic field when the spin-orbit coupling is strong.
(2) We achieved a substantial spin-charge conversion efficiency (spin Hall angle θsh=0.24) in Bi, another strongly spin-orbit coupled material. We also succeeded in drastically controlling this large spin conversion between "substential value" and "negligibly zero".

Free Research Field

物性理論

Academic Significance and Societal Importance of the Research Achievements

結晶中の相対論効果（スピン軌道結合）と，それにより変化する磁気モーメントは，非磁性の半金属・半導体でスピン応答の核となる．しかし，磁気モーメントが具体的にどのように変わるかについては，まだ詳細が分かっていない．本研究では，スピン軌道結合の強い物質の磁気モーメントを理論・実験両面で詳細に調べ，その知見を元に劇的にスピン応答を制御することに成功した．このことは，従来考慮されてこなかった，磁気モーメントの特殊な性質を活かした，劇的なスピン応答が可能であることを強く示唆するもので，本研究により，新しいスピントロニクスの方向性が示された．