Mapping out the quasi-condensate transition through the 1D-3D dimensional crossover

TL;DR

This study investigates the transition from ideal gas to quasi-condensate in a Bose gas during the 1D to 3D crossover, revealing that the modified Yang-Yang model accurately describes the entire process and identifying different scaling behaviors at low and high temperatures.

Contribution

It demonstrates that the modified Yang-Yang model effectively describes the dimensional crossover and quasi-condensate transition in a Bose gas, highlighting temperature-dependent scaling regimes.

Findings

Transition region well described by the modified Yang-Yang model

Low-temperature scaling follows a 1D interaction-driven scenario

High-temperature scaling follows a 3D degeneracy-driven scenario

Abstract

By measuring the density fluctuations in a highly elongated weakly interacting Bose gas, we observe and quantify the transition from the ideal gas to a quasi-condensate regime throughout the dimensional crossover from a purely 1D to an almost 3D gas. We show that that the entire transition region and the dimensional crossover are described surprisingly well by the modified Yang-Yang model. Furthermore, we find that at low temperatures the linear density at the quasi-condensate transition scales according to an interaction-driven scenario of a longitudinally uniform 1D Bose gas, whereas at high temperatures it scales according to the degeneracy-driven critical scenario of transverse condensation of a 3D ideal gas.