Valley splitting and magnetic anisotropy in two-dimensional VI/MSe (M = W, Mo) heterostructures.

As a new van der Waals ferromagnetic material, VI can be used to lift the valley degeneracy of transition metal dichalcogenides at the ' and points. Here, the electronic structure and magnetic anisotropy of the VI/MSe (M = W, Mo) heterostructures are studied. The VI/WSe heterostructure is semiconducting with a band gap of 0.26 eV, while the VI/MoSe heterostructure is metallic. Considering the spin-orbit-coupling, a maximum valley splitting of 3.1 meV appears in the VI/WSe heterostructure. The biaxial strain can tune the valley splitting and magnetic anisotropy of VI/MSe heterostructures. In the VI/WSe heterostructure, which has the most stable stacking, valley splitting can be increased from 1.8 meV at 4% compressive strain to 3.1 meV at 4% tensile strain. At a biaxial strain of -2% to 4%, the VI/WSe heterostructure maintains a small perpendicular magnetic anisotropy, while the VI/MoSe heterostructure shows in-plane magnetic anisotropy under different strains. The significantly tunable electronic structure and magnetic anisotropy under biaxial strain suggest that the VI/MSe heterostructures have potential applications in spintronic devices.