Intrinsic orbital moment and prediction of a large orbital Hall effect in the 2D transition metal dichalcogenides

Orbital Hall effect (OHE) is the phenomenon of transverse flow of orbital angular momentum caused by an applied longitudinal electric field. From density-functional and tight-binding model studies, we predict the existence of a large OHE in the 2D transition metal dichalcogenides (TMDC) due to the intrinsic orbital moment induced by the broken inversion symmetry of the system. We show that monolayer TMDC, the prototypical example of broken inversion symmetric 2D material, have a hitherto-unknown intrinsic orbital moment in the momentum space, which in turn leads to a large OHE with possible applications in the newly emerging field of orbitronics. The orbital moment and the OHE appear even in absence of the spin-orbit coupling (SOC) and give rise to “valley dependent spin splitting” and spin Hall effect in presence of SOC. We show that the OHE can also be tuned by a transverse electric field due to the orbital Rashba coupling, that produces an additional orbital texture which in turn modifies the OHE.