Interaction-enabled metal-insulator phase transition in a driven quantum gas

TL;DR

This study experimentally explores how tunable interactions influence the transition between localized and diffusive energy transport in a driven 3D quantum gas, revealing an interaction-enabled dynamical phase transition.

Contribution

It demonstrates the existence of a sharp dynamical boundary induced by interactions that separates localization from diffusion in a driven quantum many-body system.

Findings

Observation of many-body dynamical localization over a wide parameter range

Mapping of the localization-delocalization phase diagram via finite-time scaling

Identification of a metal-insulator transition driven by interactions and driving amplitude

Abstract

Particle transport and energy flow are central for our understanding of a wealth of phenomena in physics and the natural sciences. Interactions are generically expected to promote ergodicity and diffusive behavior, yet quantum interference can arrest transport and prevent energy absorption, defying classical expectations. How interactions and quantum coherence compete remains a fundamental open question. Here, we experimentally investigate their interplay in a periodically driven, three-dimensional (3D) quantum gas with tunable interactions. Strikingly, we find that interactions give rise to a sharp dynamical boundary that separates localization from diffusive energy absorption. By tuning the driving amplitude and interaction strength, we map the localization-delocalization phase diagram and characterize the boundary via finite-time scaling. On the insulating side, we observe many-body dynamical localization (MBDL) for a wide range of parameters, finding arrested transport in momentum space. Near the boundary, transport becomes subdiffusive, whereas in the delocalized regime we observe classical diffusion, yielding a metal-insulator transition that we interpret in terms of localization in many-body Hilbert space. Our results exemplify an interaction-enabled dynamical phase transition in a closed Floquet many-body system and clarify how coherence and interactions jointly govern the quantum-to-classical transition.