Floquet topological phase transitions induced by uncorrelated or correlated disorder

TL;DR

This paper explores how weak uncorrelated and correlated disorder affect the topological phases of a Floquet system, revealing disorder-induced phase transitions and the robustness of edge states in a model relevant to experiments.

Contribution

It provides a detailed analysis of disorder effects on Floquet topological phases, including the role of spatial correlations and the limitations of the Born approximation.

Findings

Disorder can induce topological phase transitions in Floquet systems.

Correlated disorder has a stronger impact than uncorrelated disorder.

The Born approximation fails for systems with a ring-shaped gap.

Abstract

The impact of weak disorder and its spatial correlation on the topology of a Floquet system is not well understood so far. In this study, we investigate a model closely related to a two-dimensional Floquet system that has been realized in experiments. In the absence of disorder, we determine the phase diagram and identify a new phase characterized by edge states with alternating chirality in adjacent gaps. When weak disorder is introduced, we examine the disorder-averaged Bott index and analyze why the anomalous Floquet topological insulator is favored by both uncorrelated and correlated disorder, with the latter having a stronger effect. For a system with a ring-shaped gap, the Born approximation fails to explain the topological phase transition, unlike for a system with a point-like gap.