The equilibrium state of a trapped two-dimensional Bose gas

TL;DR

This paper investigates the equilibrium density profiles of a trapped 2D Bose gas both experimentally and numerically, revealing discrepancies in in-situ measurements but good agreement after time-of-flight expansion, advancing understanding of 2D quantum gases.

Contribution

It provides a combined experimental and numerical analysis of 2D Bose gas equilibrium states, highlighting the effects of optical density variation and the validity of the local density approximation.

Findings

Discrepancy between in-situ measurements and Quantum Monte Carlo simulations.

Good agreement between experiment and theory after time-of-flight expansion.

Identification of non-linear optical density effects in density profiles.

Abstract

We study experimentally and numerically the equilibrium density profiles of a trapped two-dimensional $^{87}$Rb Bose gas, and investigate the equation of state of the homogeneous system using the local density approximation. We find a clear discrepancy between in-situ measurements and Quantum Monte Carlo simulations, which we attribute to a non-linear variation of the optical density of the atomic cloud with its spatial density. However, good agreement between experiment and theory is recovered for the density profiles measured after time-of-flight, taking advantage of their self-similarity in a two-dimensional expansion.