Condensate fraction in a 2D Bose gas measured across the Mott-insulator transition

TL;DR

This study measures the condensate fraction in a 2D Bose gas across the superfluid to Mott-insulator transition, providing experimental validation of theoretical predictions and identifying the transition point.

Contribution

First experimental measurement of condensate fraction across the transition in a 2D Bose-Hubbard system, confirming quantum Monte Carlo calculations.

Findings

Condensate fraction vanishes at the transition point.

Experimental results agree with quantum Monte Carlo simulations.

Transition from superfluid to Mott-insulating phase identified.

Abstract

We realize a single-band 2D Bose-Hubbard system with Rb atoms in an optical lattice and measure the condensate fraction as a function of lattice depth, crossing from the superfluid to the Mott-insulating phase. We quantitatively identify the location of the superfluid to normal transition by observing when the condensed fraction vanishes. Our measurement agrees with recent quantum Monte Carlo calculations for a finite-sized 2D system to within experimental uncertainty.