Spin helical states and spin transport of the line defect in silicene lattice

We investigated the electronic structure of a silicene-like lattice with a line defect under the consideration of spin-orbit coupling. In the bulk energy gap, there are defect related bands corresponding to spin helical states localized beside the defect line: spin-up electrons flow forward on one side near to the line defect and move backward on the other side, and vice verse for spin-down electrons. When the system is subjected to random distribution of spin-flipping scatterers, electrons suffer much less spin-flipped scattering when they transport along the line defect than in the bulk. An electric gate above the line defect can tune the spin-flipped transmission, which makes the line defect as a spin-controllable waveguide.