Correlation effects in the ground state of trapped atomic Bose gases

TL;DR

This paper investigates many-body correlation effects in trapped ultracold atomic Bose gases using quantum Monte Carlo methods, revealing limitations of mean-field approaches in predicting kinetic energy behavior.

Contribution

It provides detailed quantum Monte Carlo calculations of ground state properties, highlighting the inaccuracies of mean-field and Bogoliubov methods.

Findings

Mean-field GP approach gives qualitatively incorrect kinetic energy results.

QMC data shows significant correlation effects not captured by mean-field theories.

Comparison of GP, modified GP, and Bogoliubov methods under local density approximation.

Abstract

We study the effects of many-body correlations in trapped ultracold atomic Bose gases. We calculate the ground state of the gas using a ground-state auxiliary-field quantum Monte Carlo (QMC) method [Phys. Rev. E 70, 056702 (2004)]. We examine the properties of the gas, such as the energetics, condensate fraction, real-space density, and momentum distribution, as a function of the number of particles and the scattering length. We find that the mean-field Gross-Pitaevskii (GP) approach gives qualitatively incorrect result of the kinetic energy as a function of the scattering length. We present detailed QMC data for the various quantities, and discuss the behavior of GP, modified GP, and the Bogoliubov method under a local density approximation.