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 ${\mathrm{WSe}}₂$ 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 ${\mathrm{WSe}}₂$. 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.