Spin-orbit effects on the spin and pseudospin polarization in ac-driven silicene

TL;DR

This paper investigates how periodic electric fields and spin-orbit interactions influence spin and pseudospin dynamics in silicene, revealing resonance shifts, the necessity of Rashba interaction for spin polarization, and potential topological phase distinctions.

Contribution

It provides analytical and exact solutions showing the interplay of Rashba and intrinsic spin-orbit effects on spin polarization and resonance behavior in driven silicene.

Findings

Resonance shifts in quasienergy spectrum due to spin-orbit effects.

Finite Rashba interaction is essential for nonzero spin polarization.

Topological phases can be distinguished by spin polarization dynamics.

Abstract

We study the pseudospin and spin dynamical effects in single-layer silicene due to a perpendicular electric field periodically driven and its interplay with the intrinsic and extrinsic (Rashba) spin-orbit interaction. We find that the spin nonconserving processes of the real spin of the quasiparticles in silicene, -- induced by the rather weak spin-orbit mechanisms --, manifest themselves as shifts of the resonances of its quasienergy spectrum in the low coupling regime to the driving field. We show that there is an interesting cooperative effect among the, in principle, competing Rashba and intrinsic spin-orbit contributions. This is explicitly illustrated by exact and approximated analytical solutions of the dynamical equations. In addition, we show that a finite Rashba spin-orbit interaction is indeed necessary in order to achieve a nonvanishing spin polarization. As additional feature, trivial and nontrivial topological phases might be distinguished from each other as fast or slow dynamical fluctuations of the spin polarization. We mention the possible experimental detection schemes of our theoretical results and their relevance in new practical implementation of periodically driven interactions in silicene physics and related two-dimensional systems.