Extension of the Thomas-Fermi approximation for trapped Bose-Einstein condensates with an arbitrary number of atoms

TL;DR

This paper extends the Thomas-Fermi approximation for trapped Bose-Einstein condensates by including zero-point energy, providing accurate analytical formulas valid across different atom numbers and geometries, verified by numerical simulations.

Contribution

The authors derive simple, accurate extensions of the Thomas-Fermi approximation that are valid for any atom number and various trap geometries, bridging the TF and perturbative regimes.

Findings

Analytical expressions valid across regimes

Accurate for spherical, cigar-shaped, and disk-shaped condensates

Validated by numerical 3D Gross-Pitaevskii simulations

Abstract

By incorporating the zero-point energy contribution we derive simple and accurate extensions of the usual Thomas-Fermi (TF) expressions for the ground-state properties of trapped Bose-Einstein condensates that remain valid for an arbitrary number of atoms in the mean-field regime. Specifically, we obtain approximate analytical expressions for the ground-state properties of spherical, cigar-shaped, and disk-shaped condensates that reduce to the correct analytical formulas in both the TF and the perturbative regimes, and remain valid and accurate in between these two limiting cases. Mean-field quasi-1D and -2D condensates appear as simple particular cases of our formulation. The validity of our results is corroborated by an independent numerical computation based on the 3D Gross-Pitaevskii equation.