The Mott insulator transition in two dimensions

TL;DR

This paper experimentally investigates the 2D Bose-Hubbard model using cold atoms in an optical lattice, focusing on the Mott insulator transition, and finds quantitative agreement with theoretical predictions while exploring correlation effects.

Contribution

It demonstrates the realization of the 2D Bose-Hubbard model with cold atoms and provides detailed measurements of the Mott insulating state and correlation effects.

Findings

Momentum distributions match theoretical predictions without adjustable parameters.

Correlation measurements depend strongly on lattice depth, indicating geometric effects.

Higher order corrections influence the observed correlations.

Abstract

Cold atoms confined in periodic potentials are remarkably versatile quantum systems for implementing simple models prevalent in condensed matter theory. In the current experiment, we realize the 2D Bose-Hubbard model by loading a Bose-Einstein condensate into an optical lattice, and we study the resulting Mott insulating state (a phase of matter in which atoms are localized on specific lattice sites). We measure momentum distributions which agree quantitatively with theory (no adjustable parameters). We also study correlations in atom shot nose and observe a pronounced dependence on the lattice depth, this dependence indicates geometric effects to first order and suggests deviations due to higher order corrections.