Gated Silicene as a tunable source of nearly 100\% spin-polarized electrons

We demonstrate, via first-principles calculations, that gated silicene with a low-buckled honeycomb structure posseses two gapped Dirac cones with nearly full spin-polarization at the corners of the Brillouin zone. By using this key finding, we further propose a design of a silicene-based spin-filter to switch the output spin current simply by gating without the need to switch magnetic domains. Quantum transport calculations indicate that such designs will be highly efficient (nearly 100\% spin-polarized) and robust against weak disorder and edge imperfections. We also propose a Y-shaped spin/valley separator that produces spin-polarized current at two output terminals with opposite spins.