Optical, electric and magnetic controlled ballistic conductance in monolayer WSe2: the perfect valley and spin polarizations

We study the charge and valley-spin ballistic transport through monolayer (ML) WSe2 potential barrier, of width L and height U, in the presence of an off-resonant light and ferromagnetic (FM) exchange field. We show that an electric switch is available in WSe2 by increasing U beyond the critical value U = 115 meV. Due to the band gaps of valley K and K' responding differently to off-resonant light together with the huge spin-orbit coupling (SOC) in WSe2, the perfect valley and spin polarizations are obtained. Interestingly, under the effect of electrostatic potential U = 115 meV, the valley polarization can be realized even for a tiny light intensity. Additionally, the FM exchange field can assist significantly the spin polarization in a wider region of light intensity and barrier height plane due to the large shift of spin-up and down bands. More important in our results, the highest valley and spin conductance is near 100% even under the polarized situation. These results demonstrate that WSe2 is a distinguished 2D material for novel spintronics and valleytronics in future.