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 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 state, a pair of nontrivial edge states reside in one specific valley and have a strong but opposite spin polarization. A distinctive feature of this state is that both of the spin and valley indexes of the edge states can be switched by reversing the electric field. We also present a microscopic mechanism for the origin of this 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.