Hubbard model for atomic impurities bound by the vortex lattice of a rotating BEC

TL;DR

This paper models impurity atoms in a vortex lattice of a rotating BEC using a bosonic Hubbard model with occupation-dependent parameters, revealing complex phase diagram effects.

Contribution

It introduces a Hubbard model with occupation-dependent parameters to account for strong impurity interactions in a vortex lattice environment.

Findings

Occupation dependence alters the phase diagram significantly.

Some Mott lobes disappear due to competing interactions.

Both direct and mediated interactions are crucial for accurate modeling.

Abstract

We investigate cold bosonic impurity atoms trapped in a vortex lattice formed by condensed bosons of another species. We describe the dynamics of the impurities by a bosonic Hubbard model containing occupation-dependent parameters to capture the effects of strong impurity-impurity interactions. These include both a repulsive direct interaction and an attractive effective interaction mediated by the BEC. The occupation dependence of these two competing interactions drastically affects the Hubbard model phase diagram, including causing the disappearance of some Mott lobes