We investigated the electronic structure of a silicene-like lattice with aline defect under the consideration of spin-orbit coupling. In the bulk energygap, there are defect related bands corresponding to spin helical stateslocalized beside the defect line: spin-up electrons flow forward on one sidenear to the line defect and move backward on the other side, and vice verse forspin-down electrons. When the system is subjected to random distribution ofspin-flipping scatterers, electrons suffer much less spin-flipped scatteringwhen they transport along the line defect than in the bulk. An electric gateabove the line defect can tune the spin-flipped transmission, which makes theline defect as a spin-controllable waveguide.
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