Self trapping in the two-dimensional Bose-Hubbard model

TL;DR

This paper investigates how strongly interacting bosons in a 2D lattice dynamically separate into slow and fast expanding groups after trap removal, explained by doublons and Bose enhancement effects.

Contribution

It introduces a simple model explaining the dynamical separation of bosons into different expansion regimes in a 2D Bose-Hubbard system.

Findings

Observation of dynamical separation into slow and fast expanding clouds

Correlation of expansion behavior with doublons and Bose enhancement

Analysis of momentum distribution supporting the separation mechanism

Abstract

We study the expansion of harmonically trapped bosons in a two-dimensional lattice after suddenly turning off the confining potential. We show that, in the presence of multiple occupancies per lattice site and strong interactions, the system exhibits a clear dynamical separation into slowly and rapidly expanding clouds. We discuss how this effect can be understood within a simple picture by invoking doublons and Bose enhancement. This picture is corroborated by an analysis of the momentum distribution function in the regions with slowly and rapidly expanding bosons.