Spin Torque Generated by Valley Hall Effect in WSe2

TL;DR

This paper demonstrates that monolayer WSe2 can generate spin torque via the valley Hall effect, enabling efficient charge-to-spin conversion with tunable torque efficiency and out-of-plane damping-like torques.

Contribution

It is the first to show valley Hall effect-induced spin torque in WSe2 affecting magnetization in a tunneling structure, with tunable efficiency and unique torque characteristics.

Findings

Valley Hall effect in WSe2 induces pure valley current.

Generated spin torque is comparable to conventional magnetic tunnel junctions.

Torque efficiency can be optimized via valley Hall angle and gating.

Abstract

Monolayer transition metal dichalcogenides are promising materials for spintronics due to their robust spin-valley locked valence states, enabling efficient charge-to-spin conversion via valley Hall effect with non-equilibrium spins possessing long spin diffusion lengths of hundreds of nanometers. In this work, we show that the injection of a pure valley current, induced by valley Hall effect in a WSe2 monolayer, imparts a spin torque on the magnetization of an overlaid Fe or CoFe in a tunneling structure. The torque efficiency is found to be comparable to that in conventional perpendicular magnetic tunnel junctions and can be further optimized with valley Hall angle in WSe2. The valley nature of the spin torque gives rise to out-of-plane damping-like torques in a current-in-plane configuration, vanishing charge transport perpendicular-to-the-plane as well as torque efficiency tunable through gating.