Signatures of Bose-Einstein condensation in an optical lattice

TL;DR

This paper identifies experimental signatures of Bose-Einstein condensation in an optical lattice, highlighting how momentum distribution, visibility, and peak width change at the phase transition, with implications for experimental detection.

Contribution

It introduces a fixed particle number formalism to analyze BEC signatures in optical lattices, providing new insights into observable features during the phase transition.

Findings

Sharp features in momentum distribution, visibility, and peak width at BEC transition

Two-platform structure in peak width as a clear signature

Higher platform emergence correlates with the onset of condensation

Abstract

We discuss typical experimental signatures for the Bose-Einstein condensation (BEC) of an ultracold Bose gas in an inhomogeneous optical lattice at finite temperature. Applying the Hartree-Fock-Bogoliubov-Popov formalism, we calculate quantities such as the momentum-space density distribution, visibility and peak width as the system is tuned through the superfluid to normal phase transition. Different from previous studies, we consider systems with fixed total particle number, which is of direct experimental relevance. We show that the onset of BEC is accompanied by sharp features in all these signatures, which can be probed via typical time-of-flight imaging techniques. In particular, we find a two-platform structure in the peak width across the phase transition. We show that the onset of condensation is related to the emergence of the higher platform, which can be used as an effective experimental signature.