Electric field controlled spin- and valley-polarized edge states in silicene with extrinsic Rashba effect

In the presence of extrinsic Rashba spin-orbit coupling, we find that silicene can host a new quantum anomalous Hall state with spin- and valley-polarized edge states, which can be effectively controlled by the exchange field and electric field. In this new state, the pair of nontrivial edge states reside in one specific valley and have a strong but opposite spin polarization. A distinctive feature of this new state is that both of the spin and valley index of the edge states can be switched by reversing the electric field. We also present a microscopic mechanism for the origination of the new state. Our findings provide an efficient way to control the topologically protected spin- and valley-polarized edge states, which is crucial for spintronics and valleytronics.