Valley switch effect based on monolayer WSe2 modulated by circularly polarized light and valley Zeeman field

Abstract

The high-quality monolayer (ML) WSe2 leads to the possibility of an efficient manipulation of the spin and valley degrees of freedom. Here considering valley Zeeman field, which refers to the strongly anisotropic lifting of the degeneracy of the valley pseudospin degree of freedom using an external magnetic field, we investigate the spin and valley transport properties in the ML WSe2 quantum structure with circularly polarized light. Without valley Zeeman field, it is obviously found that the valley-dependent transmission can be well modulated by the orientation of circularly polarized light. The valley-dependent transmission can be filtered by the right () circularly polarized light, while the perfect filtering effect of K valley-dependent transmission occurs when the left () circularly polarized light irradiates. In the presence of valley Zeeman field, the valley-dependent transmission presents more interesting phenomena by controlling the orientation of circularly polarized light. When the circularly polarized light is applied, the valley polarization can be turned 100% to −100% with the enhancement of the effective energy about circularly polarized light. However, irradiating the circularly polarized light only 100% valley polarization can be obtained, which is independent of the effective energy of circularly polarized light and the height of electric barrier. Moreover, the results show that the valley polarization can also be from 100% to −100% in this device by adjusting the valley Zeeman field coupled with electrical field. Thus a two-way switch is formed in this quantum structure. These intriguing features indicate that the ML WSe2 structure is a promising candidate for future valleytronics devices, for valley switch, valley filter.