Orbital Hall insulating phase in transition metal dichalcogenide monolayers*

The orbital-Hall effect (OHE), in resemblance to the spin-Hall effect (SHE), refers to the creation of a transverse flow of orbital angular momentum (OAM) that is induced by a longitudinally applied electric field. Despite that the OHE has been explored mostly in 3D metallic systems, recent theoretical results predicted the existence of OHE in 2D insulators, suggesting that it could be observable in a diverse pool of 2D materials. We showed that the 2H transition metal dichalcogenide (TMD) monolayers are orbital-Hall insulators [1]. They exhibit orbital-Hall conductivity plateaux within their main semiconducting gaps. The OHE in TMD occurs even in the absence of spin-orbit coupling, and it can be linked to exotic momentum-space Dresselhaus-like OT that arise from a combination of the orbital attributes and lattice symmetry. Our results open the possibility of using TMDs for orbital-current injection and orbital torque transfer that surpass their spin-counterparts in spin-orbitronic devices.

[1] L. M. Canonico, et al. Phys. Rev. B, 16, (2020), 161409.