Phase transitions in intrinsic magnetic topological insulator with high-frequency pumping

TL;DR

This paper studies how high-frequency light can induce and control different topological phases, including quantum anomalous Hall states, in magnetic topological insulator thin films, revealing rich phase diagrams and tunable properties.

Contribution

It introduces a model showing how polarized light and magnetic moments induce diverse topological phases, including four distinct states, in magnetic topological insulator thin films.

Findings

Circularly polarized light induces QAHI phase by breaking time-reversal symmetry.

Four different phases identified: normal insulator, QSH, and two QAHI phases.

Interplay between light and magnetic moments separates QAHI phases with opposite Chern numbers.

Abstract

In this work, we investigate the topological phase transitions in an effective model for a topological thin film with high-frequency pumping. In particular, our results show that the circularly polarized light can break the time-reversal symmetry and induce the quantum anomalous Hall insulator (QAHI) phase. Meanwhile, the bulk magnetic moment can also break the time-reversal symmetry. Therefore, it shows rich phase diagram by tunning the intensity of the light and the thickness of the thin film. Using the parameters fitted by experimental data, we give the topological phase diagram of the Cr-doped Bi$_{2}$Se$_{3}$ thin film, showing that by modulating the strength of the polarized optical field in an experimentally accessible range, there are four different phases: the normal insulator phase, the time-reversal-symmetry-broken quantum spin Hall insulator phase, and two different QAHI phases with opposite Chern numbers. Comparing with the non-doped Bi$_{2}$Se$_{3}$, it is found that the interplay between the light and bulk magnetic moment separates the two different QAHI phases with opposite Chern numbers. The results show that an intrinsic magnetic topological insulator with high-frequency pumping is an ideal platform for further exploring various topological phenomena with a spontaneously broken time-reversal symmetry.