Effect of a velocity barrier on the spin- and valley-dependent transport in ferromagnetic silicene

We investigate the transport properties in a ferromagnetic silicene sheet in the presence of a velocity barrier, defining the region in which the Fermi velocity vF is tunable compared to other regions. It is shown that the valley and spin transports could be modulated by a pure velocity barrier. To achieve the high spin and valley polarization more efficiently, a local gate voltage is considered in the velocity barrier region, to induce a on-site potential difference between two sublattices of the silicene sheet. For the Fermi velocity inside the barrier smaller than the other regions, it is found that a velocity barrier induces a strong oscillation in the conductance and the valley and spin polarizations are strongly enhanced. In the opposite case, the valley and spin polarizations are suppressed by the velocity barrier. In particular, there exists a sharp transition of the polarizations by varying the Fermi velocity in this case, which has a potential application in the spin- and valley-polarized devices.