Finite Size Effect on Correlation Functions of a Bose Gas in a Trap and Destruction of the Order Parameter by Phase Fluctuations

TL;DR

This paper investigates how finite size effects influence the correlation functions of a trapped 3D Bose gas, revealing that phase fluctuations destroy the order parameter and alter correlation decay compared to infinite systems.

Contribution

It demonstrates the significant impact of finite size on correlation functions and phase fluctuations in Bose gases, highlighting differences from infinite systems.

Findings

Anomalous correlation function vanishes due to diverging phase fluctuations.

Normal correlation function decays exponentially over time.

Finite size effects critically alter coherence properties of Bose gases.

Abstract

The influence of the finite sizes on the coherent properties of 3D Bose systems is considered. As is shown, the correlation functions of a Bose gas in a trap have essential differences from analogous correlation functions in an infinite system. Thus, the anomalous correlation function vanishes due to the divergency of phase fluctuations which destruct the order parameter too. The normal correlation function decays exponentially in time for sufficiently large time interval.