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 $U=115meV$. Due to the band gaps of valley $K$ and $K^{\prime }$ 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 $U=115meV$, 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. (paper)