Characteristics of Bose-Einstein condensation in an optical lattice

TL;DR

This paper explores experimental signatures of Bose-Einstein condensation in ultracold gases within optical lattices, emphasizing momentum-space profiles and interference patterns as indicators of the phase transition.

Contribution

It introduces a method to identify BEC transition via momentum distribution and interference visibility, offering a universal and practical signature for experiments.

Findings

Bimodal structure in momentum distribution signals BEC transition

Interference pattern visibility correlates with condensate formation

Momentum distribution can estimate condensate fraction and temperature

Abstract

We discuss several possible experimental signatures of the Bose-Einstein condensation (BEC) transition for an ultracold Bose gas in an inhomogeneous optical lattice. Based on the commonly used time-of-flight imaging technique, we show that the momentum-space density profile in the first Brillouin zone, supplemented by the visibility of interference patterns, provides valuable information about the system. In particular, by crossing the BEC transition temperature, the appearance of a clear bimodal structure sets a qualitative and universal signature of this phase transition. Furthermore, the momentum distribution can also be applied to extract the condensate fraction, which may serve as a promising thermometer in such a system.