Localization persisting under aperiodic driving

TL;DR

This paper demonstrates that a hidden conservation law in a disordered spin chain can protect localization even under aperiodic driving, leading to long-lived localization without eigenstates, and shows how adding disorder can induce delocalization.

Contribution

It uncovers a hidden conservation law from chiral symmetry that sustains localization under aperiodic drives, a novel insight in driven disordered quantum systems.

Findings

Localization persists indefinitely under aperiodic drives due to a hidden conservation law.

Adding disorder that breaks the conservation law leads to delocalization.

The system exhibits long-lived prethermal regimes before eventual thermalization.

Abstract

Localization may survive in periodically driven (Floquet) quantum systems, but is generally unstable for aperiodic drives. In this work, we identify a hidden conservation law originating from a chiral symmetry in a disordered spin-1/2 XX chain. This protects indefinitely long-lived localization for general--even aperiodic--drives. Therefore, rather counter-intuitively, adding further potential disorder which spoils the conservation law delocalizes the system, via a controllable parametrically long-lived prethermal regime. This provides a first example of persistent single-particle `localization without eigenstates'.