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

TL;DR

This paper demonstrates through first-principles calculations that field-gated silicene can generate nearly 100% spin-polarized electrons, enabling electrically switchable spin filters and spin/valley separation in 2D silicon-based materials.

Contribution

It introduces a novel silicene-based device design for high-efficiency, electrically controllable spin-polarized electron sources and spin/valley separation, leveraging buckled structure and electric field tuning.

Findings

Silicene exhibits two gapped Dirac cones with nearly 100% spin polarization.

Proposed spin-filter device can switch spin polarization electrically.

Device performance remains robust against disorder and imperfections.

Abstract

Silicene is a one-atom-thick 2D 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.