# Optically induced topological states on the surface of mercury telluride

## TL;DR

This paper presents a theoretical study on how circularly polarized light can induce topological surface states in mercury telluride, transforming it from a gapless semiconductor into a topological insulator with unique surface modes.

## Contribution

The study develops a theoretical framework for Floquet engineering of surface states in HgTe using circularly polarized light, revealing optically induced topological states and band gaps.

## Key findings

- Optical irradiation induces topological surface states in HgTe.
- Irradiation opens a band gap, turning HgTe into a topological insulator.
- Induced states differ significantly from non-topological surface states.

## Abstract

We developed the theory which describes the Floquet engineering of surface electronic modes in bulk mercury telluride (HgTe) by a circularly polarized electromagnetic field. The analysis shows that the field results in appearance of the surface states which arise from the mixing of conduction and valence bands of HgTe. Their branches lie near the center of the Brillouin zone and have the Dirac dispersion characteristic for topological states. Besides them, the irradiation induces the gap between the conduction and valence bands of HgTe. Thus, the irradiation can turn mercury telluride into topological insulator from gapless semiconductor. It is demonstrated that the optically induced states differ substantially from the non-topological surface states existing in HgTe without irradiation. The structure of the found states is studied both analytically and numerically in the broad range of their parameters.