Effective thermalization of a many-body dynamically localized Bose gas

TL;DR

This paper demonstrates that a strongly interacting, periodically driven Bose gas in a dynamically localized phase behaves as an effectively thermal system, showing thermal-like momentum distribution decay and loss of coherence, contrary to typical many-body localization.

Contribution

It reveals that in the Tonks regime, dynamical localization results in an effectively thermal state, contrasting with standard many-body localized phases.

Findings

The many-body localized phase is effectively thermal in the Tonks regime.

Momentum distribution exhibits a power-law decay characterized by an effective temperature.

The phase shows loss of coherence at large distances and thermal-like Tan's contact.

Abstract

Dynamical localization is the analog of Anderson localization in momentum space, where the system's energy saturates and the single-particle wave-functions are exponentially localized in momentum space. In the presence of interactions, in the context of a periodically kicked Bose gas, it has been argued that dynamical localization persists. Focusing on the Tonks (strongly interacting) regime, we show that the many-body dynamically localized phase is effectively thermal, a clear deviation from the breaking of ergodicity observed in standard many-body localized systems. We relate the effective temperature to the driving parameters, and thus quantitatively describe the loss of coherence at large distances in this phase. Contrary to the non-interacting case, the momentum distribution decays as a power-law at large momenta, characterized by an effectively thermal Tan's contact. This is a rare example where driving and many-body (dynamical) localization lead to an effectively ergodic state.