Tunable valley characteristics of WSe2 and WSe2/VSe2 heterostructure

Abstract

Information technology can be improved by using the magnetic proximity effect to control two-dimensional valleytronics. Ferrovalley materials attract wide attention because of spontaneous valley polarization and magnetism. Here, the first-principles density functional theory has been used to examine the valley characteristics of monolayer WSe2 caused by the ferrovalley VSe2 substrate. The results demonstrate that monolayer WSe2 experiences the largest spin and absolute valley splitting at energies of 466 and 8.223 meV, respectively. With the k•p model, the effective Zeeman magnetic field of 73.36 T was found for the most stable configuration. More intriguingly, due to the ferrovalley nature of VSe2 substrates, just one valley state at the K' point exhibits a single valley-dependent optical transition in WSe2/VSe2 heterostructure. Additionally, the strain is applied to modify the spin-valley splitting. With the in-plane strain effect, the sign-reversible with the reversed spin state is obtained in biaxial strain, and a fascinating type-I to type-III band alignment transition occurs in the WSe2/VSe2, which intensifies the valley splitting. In vertical strain, the pure spin-valley polarization of the WSe2/VSe2 heterostructure can be observed. Ferrovalley substrates provide new opportunities for valleytronics applications.