Tunable spin transport and quantum phase transitions in silicene materials and superlattices

Abstract

In this paper, we study spin transport properties of silicene structures such as ribbons and superlattices with the Kane–Mele model. We investigate the effects of ferromagnetic and antiferromagnetic exchange fields, vertical and transverse electric fields and defects on the band structure, density of states, as well as conductance of the system. Our calculated results indicate that by applying a vertical electric field and/or an antiferromagnetic exchange field, metal–semimetal and also metal–semiconductor quantum phase transitions occur. We show that a zigzag silicene ribbon, when exposed to a transverse electric field in combination with an antiferromagnetic exchange field, behaves as a half-metal that allows one spin state electrons to move. Furthermore, under a vertical electric field and in the simultaneous presence of ferromagnetic and antiferromagnetic exchange fields applied to two half-widths of the ribbon, we observe the half-metallic phase. Our results help to control spin currents and to have new applications in silicene spintronics.