Gated silicene as a tunable source of nearly 100% spin-polarized electrons

Abstract

Silicene is a one-atom-thick two-dimensional crystal of silicon with a hexagonal lattice structure that is related to that of graphene but with atomic bonds that are buckled rather than flat. This buckling confers advantages on silicene over graphene, because it should, in principle, generate both a band gap and polarized spin-states that can be controlled with a perpendicular electric field. Here we use first-principles calculations to show that field-gated silicene possesses two gapped Dirac cones exhibiting nearly 100% spin-polarization, situated at the corners of the Brillouin zone. Using this fact, we propose a design for a silicene-based spin-filter that should enable the spin-polarization of an output current to be switched electrically, without switching external magnetic fields. Our quantum transport calculations indicate that the proposed designs will be highly efficient (nearly 100% spin-polarization) and robust against weak disorder and edge imperfections. We also propose a Y-shaped spin/valley separator that produces spin-polarized current at two output terminals with opposite spins.

Colloquium: Topological band theory

“…(Hasan and Kane 2010;Qi and Zhang 2011;Mas-Ballesté et al 2011;Butler et al 2013;Tsai et al 2013) By examining how band structures evolve under spin-orbit interaction, many topologically interesting materials have been predicted. Theoretically predicted 3D TIs span binary, ternary and quaternary compounds, transition metal and f-electron systems, Weyl and 3D Dirac semimetals, complex oxides, organometallics, skutterudites and antiperovskites as summarized in the materials inventory given in the Appendix.…”

Electro-absorption of silicene and bilayer graphene quantum dots

“…Non-planar graphene-derivative materials have attracted considerable attention [1][2][3][4][5][6][7][8] because of their tunable electronic properties, different from those of the single-layer graphene. Application of the electric field, E, across the bilayer (multilayer) graphene system opens a gap between the conduction and valence bands.…”

“…The possibility of controlling the gap offers a wealth of new routes for the next generation of field effect transistors and optoelectronic devices. 1,2,13 However, the on-chip nanoscale realization of such devices requires finite-size components like nanoribbons and nanoflakes or quantum dots (QDs). 14 Therefore, a deeper understanding of their individual electronic properties, which can be substantially different from those in infinite systems because of the finite-size electronic confinement, 15 is needed.…”

“…[9][10][11][12] The same also happens with silicene because of the buckling of its honeycomb lattice. [2][3][4]6 The atoms of the type A and B of the lattice are displaced alternatively in the vertical direction and are subjected to a different, electric field producing, potential gradient. The possibility of controlling the gap offers a wealth of new routes for the next generation of field effect transistors and optoelectronic devices.…”

Proximity-induced spin-valley polarization in silicene or germanene on F-doped WS2

“…While this is difficult to realize in graphene, the stronger SOC and buckled lattice of silicene or germanene provide an avenue to access and control the valley degree of freedom [24]. Spin and valley polarization can be achieved by means of doping and decoration with certain 3d or 4d transition metals [25,26] as well as by an external electric field [4,5,27]. However, interaction with the substrate is typically detrimental, because the electronic states * udo.schwingenschlogl@kaust.edu.sa are perturbed [28].…”