Spin torque generated by valley Hall effect in WSe2

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 the valley Hall effect with nonequilibrium spins possessing long spin diffusion lengths of hundreds of nanometers. In this paper, we show that the injection of a pure valley current, induced by the 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 the valley Hall angle in WSe2. The valley nature of the spin torque gives rise to out-of-plane dampinglike torques in a current-in-plane configuration, vanishing charge transport perpendicular to the plane, as well as torque efficiency tunable through gating.