Twist-Tunable Spin-to-Charge Conversion and Valley-Contrasting Effects in Graphene/TMDC Heterostructures

Abstract: We consider graphene deposited on monolayers of such transition-metal dichalcogenides like MoSe$_2$, WSe$_2$, MoS$_2$, and WS$_2$. Our key objective is to study the impact of relative twist angle between the monolayers on the proximity-induced spin-orbital effects and orbital phenomena in graphene. To do this we used an effective model Hamiltonian for low-energy states, taken from available literature. The Green function formalism is used to calculate analytical formula for the spin Hall effect and nonequilibrium spin polarization in the system. We also determine the valley Hall and valley polarization effects, and their dependence on the twist angle. We have shown that the valley Hall conductivity can take the quantized value equal to $\pm 2 e^2/h$.