AC/DC Spin and Valley Hall Effects in Silicene and Germanene

TL;DR

This paper theoretically investigates the spin and valley Hall effects in silicene and germanene, highlighting how electric fields, doping, and phase type influence their conductivities and potential for controlled spin-valley accumulation.

Contribution

It provides new analytical insights into how intrinsic spin-orbit coupling and external tuning parameters affect Hall conductivities in 2D materials.

Findings

Hall conductivities depend on insulating phase type.

Finite frequency enhances Hall response at interband transition energies.

Electric field tuning controls spin and valley flow directions.

Abstract

The intrinsic spin and valley Hall conductivities of silicene, germanene and other similar two dimensional crystals are explored theoretically. Particular attention is given to the effects of the intrinsic spin-orbit coupling, electron doping and the type of insulating phase of the system (i.e., a topological insulator or a band insulator) which can be tuned by a perpendicular electric field. At finite frequency, the transverse edge to which carriers of particular spin and valley label flow can be controlled such that an accumulation of a particular combination of spin and valley index can be obtained. The direction of flow is found to be dependent on the type of insulating phase. The magnitude of the Hall conductivity response is enhanced from the DC values at certain incident photon frequencies associated with the onset of interband transitions. Analytic results are presented for both the DC and finite frequency results.