Orbital Edelstein effect in monolayer transition metal dichalcogenides

The Edelstein effect consists of the non-equilibrium accumulation of magnetization in response to an electric field in systems with broken inversion symmetry. The spin Edelstein effect (SEE) is a well-established phenomenon, where the magnetization comes from the spin moments. The orbital Edelstein effect (OEE) is the orbital counterpart, where the magnetization comes from the orbital moments rather than the spin moments. Here, we predict the existence of a large OEE in monolayer transition-metal dichalcogenides (TMD) in the presence of a symmetry-breaking perpendicular electric field. The predicted OEE is substantially larger than the SEE. The effect should exist both in doped insulating TMDs such as WS₂ as well as in metallic TMDs such as NbSe₂, where a Fermi surface already exists without doping. Analytical expressions for both spin and orbital Edelstein effect are derived for the TMDs, and their magnitudes calculated using density-functional theory by taking WS₂ as an example. Our work suggests the TMDs to be prime candidates for studying the OEE. Our results are relevant for spin-injection experiments, where the Edelstein effect plays a role.