Dilute resonating gases and the third virial coefficient

TL;DR

This paper investigates dilute gases with large scattering lengths, revealing universal behavior in thermodynamics and emphasizing the significance of three-body physics in the third virial coefficient.

Contribution

It provides the first calculation of the third virial coefficient in dilute gases with large scattering lengths, highlighting the role of three-body interactions.

Findings

The third virial coefficient depends on a new three-body parameter.

For many parameter values, the $z^3$ term dominates the expansion.

Universal behavior is observed between the condensation temperature and the potential range.

Abstract

We study dilute gases with short range interactions and large two-body scattering lengths. At temperatures between the condensation temperature and the scale set by therange of the potential there is a high degree of universality. The first two terms in the expansion of thermodynamic functions in powers of the fugacity $z$, which measures the diluteness of the system, are determined by the scattering length only. The term proportional to $z^3$ depends only on one new parameter describing the three-body physics. We compute the third term of the expansion and show that, for many values of this new parameter, the $z^3$ term may be the dominant one.