Theory of unitary Bose gases

TL;DR

This paper develops an analytical framework for describing atomic Bose gases at unitarity, deriving universal properties and connecting to known theories in different interaction regimes.

Contribution

It introduces a new analytical approach to characterize the properties of unitary Bose gases, extending to finite scattering lengths and linking to Bogoliubov theory.

Findings

Derived universal properties like chemical potential and contact

Established the speed of sound and condensate density at unitarity

Connected the theory to weak-coupling limits and Bogoliubov theory

Abstract

We develop an analytical approach for the description of an atomic Bose gas at unitarity. By focusing in first instance on the evaluation of the single-particle density matrix, we derive several universal properties of the unitary Bose gas, such as the chemical potential, the contact, the speed of sound, the condensate density and the effective interatomic interaction. The theory is also generalized to describe Bose gases with a finite scattering length and then reduces to the Bogoliubov theory in the weak-coupling limit.