Quasiperiodicity protects quantized transport in disordered systems without gaps

TL;DR

This paper demonstrates that quasiperiodicity can protect quantized transport in disordered systems without energy gaps, using a driven Aubry-André-Harper model, and proposes experimental protocols for topological state preparation.

Contribution

It reveals that topological quantized currents remain stable beyond gap closing in disordered quasiperiodic systems and introduces a practical protocol for realizing high Chern number states.

Findings

Quantized currents survive disorder beyond gap closing.

Robustness explained via Landau-Zener transitions in configuration space.

Proposes experimental methods for topological state preparation.

Abstract

The robustness of topological properties, such as quantized currents, generally depends on the existence of gaps surrounding the relevant energy levels or on symmetry-forbidden transitions. Here, we observe quantized currents that survive the addition of bounded local disorder beyond the closing of the relevant instantaneous energy gaps in a driven Aubry-Andr\'e-Harper chain, a prototypical model of quasiperiodic systems. We explain the robustness using a local picture in \textit{configuration-space} based on Landau-Zener transitions, which rests on the Anderson localisation of the eigenstates. Moreover, we propose a protocol, directly realizable in for instance cold atoms or photonic experiments, which leverages this stability to prepare topological many-body states with high Chern numbers and opens new experimental avenues for the study of both the integer and fractional quantum Hall effects.