Generation of current-induced spin polarization due to the locally-broken spatial inversion symmetry

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03413
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: Hokkaido University
• Principal Investigator: AKERA Hiroshi 北海道大学, 工学研究院, 教授 (20184129)
• Co-Investigator(Kenkyū-buntansha): 江上 喜幸 北海道大学, 工学研究院, 助教 (20397631)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: スピントロニクス / 原子鎖

Outline of Final Research Achievements

A system with broken spatial inversion symmetry produces the polarization of the spin angular momentum in the presence of current (current-induced spin polarization, CISP), while a system with the spatial inversion symmetry broken locally around an atom exhibits the CISP at the atom. This work has focused on a fundamental helical system, that is an atomic chain along a helix, and shown that the local CISP at each atom strongly depends on the curvature and the torsion which determine the extent of broken spatial inversion symmetry at each atom. Moreover it is found that the helical atomic chain exhibits the spin-velocity locking in which the spin orientation is determined by the direction of electron motion. This locking realizes the current with a high spin polarization at low enough temperatures.

Free Research Field

物性理論

Academic Significance and Societal Importance of the Research Achievements

本研究の成果は、基本系としての螺旋状原子鎖を対象に、系の空間反転対称性の破れの度合いを表す曲率・捩率と電流誘起スピン偏極との間の関係を解明したという物理学上の意義をもつとともに、電流誘起スピン偏極と電流のスピン偏極度という特性を向上させるための指針として工学的意義をもつ。電流誘起スピン偏極から取り出されるスピン流やスピン偏極電流はスピントロニクスにおいて磁化反転に用いられているので社会的にも波及効果が期待できる。