Density-functional prediction of a strong Orbital Hall effect in the monolayer WX₂ (X = Te, S)

The orbital Hall effect (OHE) is the transverse flow of the orbital angular momentum in response to the applied electric field, analogous to the charge current flow in the standard Hall effect. Even though the OHE has been proposed about a decade ago, it has not been directly observed experimentally to our knowledge. We have recently proposed that the 2D transition metal dichalcogenides (TMDC) with non-centrosymmetric crystal structure may be a good candidate for a robust OHE. In this talk, we evaluate the effect for the 2D-TMDC materials WTe₂ and WS₂ where there is a strong spin-orbit coupling present, both for the non-centrosymmetric (2H) and the centrosymmeteic (1T') cases. As anticipated, the OHE in the 2H structure is much stronger, due to the existence of the intrinsic orbital moment in different parts of the Brillouin zone, which flow in different directions, as opposed to the centrosymmeteic (1T') structure, where the OHE occurs due to the induced orbital moment in the presence of the Hall electric field. Our results are based on density-functional calculations as well as minimal tight-binding models.