Interacting Stark localization dynamics in a three-dimensional lattice Bose gas

TL;DR

This study investigates the slow thermalization process of a Stark localized Bose gas in a three-dimensional lattice, revealing that interactions and heating are not primary causes, and suggesting a continuum theory may be necessary.

Contribution

It provides the first detailed measurement of thermalization dynamics in a 3D Stark localized Bose gas, highlighting the slow, non-exponential nature of equilibration.

Findings

Equilibrium is achieved at all sampled lattice depths.

Thermalization is slow, taking up to 500 tunneling times.

Hubbard U term and lattice-light heating are not responsible for thermalization.

Abstract

We measure the thermalization dynamics of a lattice Bose gas that is Stark localized by a parabolic potential. A non-equilibrium thermal density distribution is created by quickly removing an optical barrier. The resulting spatio-temporal dynamics are resolved using Mardia's $B$ statistic, which is a measure sensitive to the shape of the entire density distribution. We conclude that equilibrium is achieved for all lattice potential depths that we sample, including the strongly interacting and localized regime. However, thermalization is slow and non-exponential, requiring up to 500 tunneling times. We show that the Hubbard $U$ term is not responsible for thermalization via comparison to an exact diagonalization calculation, and we rule out equilibration driven by lattice-light heating by varying the laser wavelength. The thermalization timescale is comparable to the next-nearest-neighbor tunneling time, which suggests that a continuum, strongly interacting theory may be needed to understand equlibration in this system.