Dynamics and Thermodynamics of the Low-Temperature Strongly Interacting Bose Gas

TL;DR

This study measures the zero-temperature equation of state of a homogeneous Bose gas, revealing deviations from mean-field theory at strong interactions and providing insights into many-body effects and universal behavior near unitarity.

Contribution

It provides the first quantitative experimental test of Lee-Huang-Yang corrections in a homogeneous Bose gas and explores the dynamic response across interaction regimes.

Findings

Observed departure from mean-field theory with increasing interactions

Quantified many-body corrections consistent with Lee-Huang-Yang predictions

Established a lower bound for the universal constant at unitarity: ξ > 0.44(8)

Abstract

We measure the zero-temperature equation of state of a homogeneous Bose gas of $^7$Li atoms by analyzing the \emph{in-situ} density distributions of trapped samples. For increasing repulsive interactions our data shows a clear departure from mean-field theory and provides a quantitative test of the many-body corrections first predicted in 1957 by Lee, Huang and Yang. We further probe the dynamic response of the Bose gas to a varying interaction strength and compare it to simple theoretical models. We deduce a lower bound for the value of the universal constant $\xi>0.44(8)$ that would characterize the universal Bose gas at the unitary limit.