Tunable valley filter efficiency by spin–orbit coupling in silicene nanoconstrictions* *Project supported by the Natural Science Foundation of Zhejiang Province, China (Grant No. LQ17A040001), the National Natural Science Foundation of China (Grant Nos. 61874078, 11647046, and 61904125), the National Key Research and Development Program of China (Grant No. 2018YFB2202100), and the Science and Technology Planning Project of Wenzhou City (Grant

Abstract

Valley filter is a promising device for producing valley polarized current in graphene-like two-dimensional honeycomb lattice materials. The relatively large spin–orbit coupling in silicene contributes to remarkable quantum spin Hall effect, which leads to distinctive valley-dependent transport properties compared with intrinsic graphene. In this paper, quantized conductance and valley polarization in silicene nanoconstrictions are theoretically investigated in quantum spin-Hall insulator phase. Nearly perfect valley filter effect is found by aligning the gate voltage in the central constriction region. However, the valley polarization plateaus are shifted with the increase of spin–orbit coupling strength, accompanied by smooth variation of polarization reversal. Our findings provide new strategies to control the valley polarization in valleytronic devices.