Controllable photo-induced spin and valley filtering in silicene

TL;DR

This paper demonstrates how off-resonant circularly polarized light and electric fields can be used to control spin and valley polarization in silicene, enabling tunable and reversible filtering effects.

Contribution

It introduces a method to achieve controllable spin and valley filtering in silicene using light and electric fields, with detailed analysis of the conditions for perfect polarization.

Findings

Conductance can be spin- or valley-polarized.

Polarization can be tuned and inverted by electric field and light polarization.

Perfect filtering achieved under specific conditions.

Abstract

We study ballistic transport of Dirac electrons through a strip in silicene, when the strip is exposed to off-resonant circularly polarized light and an electric field applied perpendicular to the silicene plane. We show that the conductance through the strip is spin- or/and valley-polarized. This can be explained by spin-valley coupling in silicene, and modification of its band structure through virtual absorption/emission processes and also by the perpendicular electric field. The spin- (valley-) polarization can be enhanced by tuning the light intensity and the value of the perpendicular electric field, leading to perfect spin (valley) filtering for certain of their values. Further, the spin (valley) polarization can be inverted by reversing the perpendicular electric field (by reversing the perpendicular electric field or reversing the circular polarization of the light irradiation). The conditions necessary for the fully valley polarization is determined.