Light-induced topological phases in thin films of magnetically doped topological insulators

TL;DR

This paper investigates how off-resonance circularly polarized light can induce and control topological phases in magnetically doped topological insulator thin films, revealing novel phases like quantum pseudo-spin Hall insulators.

Contribution

It demonstrates light-induced topological phase transitions, including quantum anomalous Hall and pseudo-spin Hall phases, in magnetically doped topological insulator thin films without external magnetic fields.

Findings

Light induces quantum anomalous Hall phase without magnetic field.

Emergence of quantum pseudo-spin Hall insulator with anisotropic edge states.

Topological phases confirmed by Hall conductivity and Chern number calculations.

Abstract

We study the photon-dressed electronic band structure of topological insulator thin films which could be also doped doped by magnetic impurities in response to an off-resonance time-periodic electromagnetic field. The thin films irradiated by a circularly polarized light undergo phase transition, in a driven system made by and a fascinating feature of distinct phases emerges in the phase diagram depending on the parameters such as frequency, intensity and polarization of the light. As a particular case, quantum anomalous Hall insulator phase is induced purely by the light-induced mass term with no need to any external magnetic field or even magnetization arising from the doped-doping magnetic impurities. Moreover, a novel phase, quantum pseudo-spin Hall insulator, emerges in the phase diagram leading to anisotropic helical edge states with zero total Chern number. We verify these achievements in the phase diagrams are supported by numerical calculations for a nanoribbon of the thin film for which the edge mode behavior is observed at several points on the phase diagram. The emergence of the mentioned topological phases and the edge modes are further confirmed by both calculating the Hall conductivity by means of the Kubo formula and the Chern number of each band. The effect of light parameters on the Landau level fan diagram in the presence of a perpendicular magnetic field indicates various topological phases occurring at higher Chern numbers.