Electric field induced giant valley polarization in two dimensional ferromagnetic WSe2/CrSnSe3 heterostructure

Valleytronics is receiving extensive research efforts. Thus, we investigated the electric field-induced valley polarization in the WSe2/CrSnSe3 heterostructures by varying the stacking order. The heterostructure shows indirect band gaps of 270 and 330meV in the two most stable structures. The WSe2/CrSnSe3 heterostructure displays a ferromagnetic ground state with out-of-plane anisotropy (0.02meV) in one stable stacking (S-1) while a small in-plane anisotropy (-0.01meV) is found in other stacking (S-2). The Curie temperature is slightly enhanced to 73K compared to the monolayer CrSnSe3. We have found the valley splitting of 4meV in S-1 whereas it became 9meV in the S-2 system. The valley splitting is further enhanced if an electric field is applied from CrSnSe3 to the WSe2 layer whereas it is suppressed in the reversed electric field. Particularly, the S-2 structure shows a giant valley splitting of 67meV at an electric field of 0.6V angstrom(-1). We attribute this electric field-dependency to the dipolar effect. Overall, we propose that the WSe2/CrSnSe3 heterostructure can be a potential structure for obtaining a giant valley splitting.