Measuring a localization phase diagram controlled by the interplay of disorder and driving

TL;DR

This study experimentally maps the phase diagram of a 1D quasiperiodic cold-atom system under periodic driving, revealing complex localization behaviors influenced by both disorder and drive strength, and highlighting the need for extended theoretical models.

Contribution

The paper provides the first experimental exploration of the combined effects of quasiperiodic disorder and periodic driving on localization, revealing deviations from existing high-frequency Floquet theories.

Findings

Observation of metallic lobes bounded by quantum phase transitions

Deviations from high-frequency theoretical predictions at lower drive frequencies

Necessity to extend Floquet theories to explain experimental results

Abstract

The interplay of various localizing mechanisms is a central topic of modern condensed matter physics. In this work we experimentally explore the interplay between quasiperiodic disorder and periodic driving, each of which in isolation is capable of driving a metal-insulator phase transition. Using a 1D quasiperiodic cold-atom chain we measure transport across the full phase diagram varying both drive strength and quasidisorder strength. We observe lobes of metallic phases bounded by quantum phase transitions which depend on both drive and disorder. While these observations are broadly consistent with expectations from a high-drive-frequency theoretical model, we also observe clear departures from the predictions of this model, including anomalous changes in localization behavior at lower drive frequency. We demonstrate experimentally and theoretically that understanding the full measured phase diagram requires an extension to commonly-used approximate theories of Floquet matter.