Isothermal compressibility determination across Bose-Einstein condensation

TL;DR

This paper experimentally determines the isothermal compressibility of a trapped Bose gas across Bose-Einstein condensation using a global thermodynamic approach, revealing the second order phase transition nature.

Contribution

It introduces a global variables method for measuring compressibility, offering advantages over local density approximation in studying phase transitions.

Findings

Behavior of compressibility around the critical point identified

Second order nature of the phase transition confirmed

Global variables approach proved effective for thermodynamic measurements

Abstract

We apply the global thermodynamic variables approach to experimentally determine the isothermal compressibility parameter $\kappa_T$ of a trapped Bose gas across the phase transition. We demonstrate the behavior of $\kappa_T$ around the critical pressure, revealing the second order nature of the phase transition. Compressibility is the most important susceptibility to characterize the system. The use of global variables shows advantages with respect to the usual local density approximation method and can be applied to a broad range of situations.