Valley-dependent spin-orbit torques in two dimensional hexagonal crystals

TL;DR

This paper investigates valley-dependent spin-orbit torques in 2D hexagonal crystals, revealing how valley polarization can be controlled via external parameters, enabling tunable spintronic functionalities.

Contribution

It introduces the concept of valley-dependent spin-orbit torques in 2D materials and demonstrates how to control valley imbalance for tunable spintronic effects.

Findings

Valley imbalance can reach 100% with bias voltage or magnetization control.

Spin-orbit torque components include field-like and antidamping terms.

Berry curvature influences the antidamping torque in these materials.

Abstract

We study spin-orbit torques in two dimensional hexagonal crystals such as graphene, silicene, germanene and stanene. The torque possesses two components, a field-like term due to inverse spin galvanic effect and an antidamping torque originating from Berry curvature in mixed spin-$k$ space. In the presence of staggered potential and exchange field, the valley degeneracy can be lifted and we obtain a valley-dependent Berry curvature, leading to a tunable antidamping torque by controlling the valley degree of freedom. The valley imbalance can be as high as 100\% by tuning the bias voltage or magnetization angle. These findings open new venues for the development of current-driven spin-orbit torques by structural design.