Two and Three-body Contacts in the Unitary Bose Gas

TL;DR

This paper demonstrates that in a resonantly interacting Bose gas, three-body correlations from Efimov physics are essential and measurable, extending the understanding beyond pairwise interactions in many-body quantum systems.

Contribution

The study provides the first direct measurement of three-body contact in a Bose gas, highlighting the importance of three-body correlations beyond two-body interactions.

Findings

Three-body correlations are crucial in the dynamics of the Bose gas.

Ramsey interferometry can directly measure three-body contact.

Three-body Efimov physics significantly influences many-body observables.

Abstract

In many-body systems governed by pairwise contact interactions, a wide range of observables is linked by a single parameter, the two-body contact, which quantifies two-particle correlations. This profound insight has transformed our understanding of strongly interacting Fermi gases. Here, using Ramsey interferometry, we study coherent evolution of the resonantly interacting Bose gas, and show that it cannot be explained by only pairwise correlations. Our experiments reveal the crucial role of three-body correlations arising from Efimov physics, and provide a direct measurement of the associated three-body contact.