Electrically tunable valleytronics in quantum anomalous Hall insulating transition metal trihalides

We propose a different scheme for achieving valley splitting using an electric field in the materials with inversion symmetry but without time-reversal symmetry, and apply this scheme to two-dimensional transition metal trihalides VX3 (X=Cl, Br). Based on ab initio calculations and the tight-binding model, we find few layer VX3 can be readily tuned from intrinsic quantum anomalous Hall insulators to quantum valley Hall insulators by external electric fields. Especially, the electric-field-induced valley splitting of the bilayer VX3 is extremely large, about two orders of magnitude higher than that induced by a magnetic field in the state-of-the-art valleytronic materials (e.g., MoS2 and WSe2). We further reveal rich topological phases of few layer VX3 and valley-polarized states at the phase boundary. These findings may motivate further topology and valleytronics related researches in low-dimensional transition metal compounds.