Spin-torque efficiency enhanced by Rashba spin splitting in three dimensions

TL;DR

This paper investigates how Rashba spin splitting in three-dimensional materials enhances spin-torque efficiency, revealing optimal conditions for maximum efficiency related to Fermi energy and Rashba parameters.

Contribution

It provides an analytical study of spin torque in 3D Rashba systems, linking spin topology with Fermi energy dependence and identifying conditions for optimal spin-torque efficiency.

Findings

High spin-torque efficiency occurs when Fermi energy is on the lower band.

Maximum efficiency is achieved at an optimal Rashba parameter.

Spin-torque efficiency is related to the Fermi surface topology.

Abstract

We examine a spin torque induced by the Rashba spin-orbit coupling in three dimensions within the Boltzmann transport theory. We analytically calculate the spin torque and show how its behavior is related with the spin topology in the Fermi surfaces by studying the Fermi-energy dependence of the spin torque. Moreover we discuss the spin-torque efficiency which is the spin torque divided by the applied electric current in association with the current-induced magnetization reversal. It is found that high spin-torque efficiency is achieved when the Fermi energy lies on only the lower band and there exists an optimal value for the Rashba parameter, where the spin-torque efficiency becomes maximum.