Floquet topological transitions in extended Kane-Mele models with disorder

TL;DR

This paper uses Floquet theory to show how circularly polarized light can induce and control topological phase transitions in disordered extended Kane-Mele models, revealing laser-dependent topological behaviors and Floquet topological Anderson transitions.

Contribution

It demonstrates how light can induce and manipulate topological phases in disordered systems, extending the Kane-Mele model with new hopping terms and analyzing the effects of disorder and laser parameters.

Findings

Circularly polarized light induces topological transitions.

Disorder can cause Floquet topological Anderson transitions.

Minimal gap points shift in the Brillouin zone with laser parameters.

Abstract

In this work we use Floquet theory to theoretically study the influence of circularly polarized light on disordered two-dimensional models exhibiting topological transitions. We find circularly polarized light can induce a topological transition in extended Kane-Mele models that include additional hopping terms and on-site disorder. The topological transitions are understood from the Floquet-Bloch band structure of the clean system at high symmetry points in the first Brillouin zone. The light modifies the equilibrium band structure of the clean system in such a way that the smallest gap in the Brillouin zone can be shifted from the $M$ points to the $K(K')$ points, the $\Gamma$ point, or even other lower symmetry points. The movement of the minimal gap point through the Brillouin zone as a function of laser parameters is explained in the high frequency regime through the Magnus expansion. In the disordered model, we compute the Bott index to reveal topological phases and transitions. The disorder can induce transitions from topologically non-trivial states to trivial states or vice versa, both examples of Floquet topological Anderson transitions. As a result of the movement of the minimal gap point through the Brillouin zone as a function of laser parameters, the nature of the topological phases and transitions is laser-parameter dependent--a contrasting behavior to the Kane-Mele model.