Supercurrent-Induced Spin-Orbit Torques

TL;DR

This paper theoretically explores how supercurrents induce spin-orbit torques in a 2D ferromagnetic lattice on a superconductor with strong spin-orbit coupling, revealing limits and potential for magnetization control.

Contribution

It introduces a phenomenological and microscopic framework for supercurrent-induced spin-orbit torques, highlighting their origin from spin-triplet correlations and intrinsic limitations.

Findings

Supercurrents produce reactive spin-orbit torques on magnetization.

Spin-orbit torque originates from spin-polarized Cooper pairs.

Maximum torque field estimated at 0.16 mT in certain semiconductors.

Abstract

We theoretically investigate the supercurrent-induced magnetization dynamics of a two-dimensional lattice of ferromagnetically ordered spins placed on a conventional superconductor with broken spatial inversion symmetry and strong spin-orbit coupling. We develop a phenomenological description of the coupled dynamics of the superconducting condensate and the spin system, and demonstrate that supercurrents produce a reactive spin-orbit torque on the magnetization. By performing a microscopic self-consistent calculation, we show that the spin-orbit torque originates from a spin-polarization of the Cooper pairs due to current-induced spin-triplet correlations. Interestingly, we find that there exists an intrinsic limitation for the maximum achievable spin-orbit torque, which is determined by the coupling strength between the condensate and the spin system. In proximitized hole-doped semiconductors, the maximum achievable spin-orbit torque field is estimated to be on the order of $0.16$ mT, which is comparable to the critical field for current-induced magnetization switching in ferromagnetic semiconductors.