Photoinduced pseudospin effects in silicene beyond the off resonant condition

TL;DR

This paper investigates how intense terahertz radiation can manipulate charge carriers and pseudospin polarization in silicene, revealing band inversion phenomena due to resonant photon processes beyond the off resonant approximation.

Contribution

It provides an exact analysis of pseudospin polarization and quasienergy spectrum in silicene under resonant conditions, extending beyond traditional off resonant approximations.

Findings

Resonant photon processes induce band inversion in silicene.

Effective gap manipulation occurs in intermediate and strong coupling regimes.

Pseudospin polarization inversion correlates with quasienergy spectrum changes.

Abstract

We study the photoinduced manipulation of charge carriers in monolayer silicene subject to intense electromagnetic terahertz radiation. Considering the Dirac cone approximation and going beyond the off resonant condition for large frequencies of the radiation field, where only virtual photon processes are allowed, we present the exact zero-momentum pseudospin polarization and numerical results for the quasienergy band structure and time-averaged density of states. We find that resonant processes, due to real photon emission and absorbtion processes, induce a band inversion that qualitatively modifies the quasienergy spectrum. These band structure changes manifest themselves as an inversion of the averaged pseudospin polarization. Through the analysis of the time-averaged density of states we find that effective photoinduced gap manipulation can only be achieved in the intermediate and strong matter-radiation coupling regime where the off resonant approximation breaks down.