Influence of the velocity barrier on the massive Dirac electron transport in a monolayer MoS2 quantum structure

Using the transfer matrix method, spin- and valley-dependent electron transport properties modulated by the velocity barrier were studied in the normal/ferromagnetic/normal monolayer MoS₂ quantum structure. Based on Snell’s Law in optics, we define the velocity barrier as ξ=v₂/v₁ by changing the Fermi velocity of the intermediate ferromagnetic region to obtain a deflection condition during the electron transport process in the structure. The results show that both the magnitude and the direction of spin- and valley-dependent electron polarization can be regulated by the velocity barrier. –100% polarization of spin- and valley-dependent electron can be achieved for ξ>1, while 100% polarization can be obtained for ξ<1. Furthermore, it is determined that perfect spin and valley transport always occur at a large incident angle. In addition, the spin- and valley-dependent electron transport considerably depends on the length k_FL and the gate voltage U(x) of the intermediate ferromagnetic region. These findings provide an effective method for designing novel spin and valley electronic devices.