Floquet states and optical conductivity of an irradiated two dimensional topological insulator

TL;DR

This paper investigates the topological properties and optical conductivity of a 2D topological insulator under circularly polarized light, revealing quantized Hall conductivity in ideal conditions and complex phase behavior under irradiation.

Contribution

It provides a detailed analysis of Floquet states, optical conductivity, and phase diagrams for irradiated topological insulators, including effects of different occupation models and driving regimes.

Findings

Quantized DC optical Hall conductivity in ideal occupation.

Optical transitions depend on occupation and optical weight.

Rich phase diagram with anomalous edge states under weak on-resonant drive.

Abstract

We study the topology of the Floquet states and time-averaged optical conductivity of the lattice model of a thin topological insulator subject to a circularly polarized light using the extended Kubo formalism. Two driving regimes, the off-resonant and on-resonant, and two models for the occupation of the Floquet states, the ideal and mean-energy occupation, are considered. In the ideal occupation, the real part of DC optical Hall conductivity is shown to be quantized while it is not quantized for the mean energy distribution. The optical transitions in the Floquet band structure depend strongly on the occupation and also the optical weight which consequently affect all components of optical conductivity. At high frequency regime, we present an analytical calculation of the effective Hamiltonian and also its phase diagram which depends on the tunneling energy between two surfaces. The topology of the system shows rich phases when it is irradiated by a weak on-resonant drive giving rise to emergence of anomalous edge states.