Orbital Hall insulating phase in transition metal dichalcogenide monolayers

Abstract

We show that H-phase transition metal dichalcogenide (TMD) monolayers, such as ${\mathrm{MoS}}_{2}$ and ${\mathrm{WSe}}_{2}$, are orbital Hall insulators. They present very large orbital Hall conductivity plateaus in their semiconducting gap, where the spin Hall conductivity vanishes. Our results open the possibility of using TMDs for orbital current injection and orbital torque transfers that surpass their spin-counterparts in spin-orbitronics devices. The orbital Hall effect in TMD monolayers occurs even in the absence of spin-orbit coupling. It can be linked to exotic momentum-space Dresselhaus-like orbital textures, analogous to the spin-momentum locking in two-dimensional Dirac fermions that arise from a combination of orbital attributes and lattice symmetry.