Efimov correlations in strongly interacting Bose gases

TL;DR

This paper investigates Efimov physics in strongly interacting Bose gases by calculating virial coefficients, contact parameters, and momentum distribution, revealing universal high-momentum tails and providing insights into Efimov state spectroscopy.

Contribution

It offers the first detailed theoretical analysis of Efimov correlations in a Bose gas using virial expansion up to third order, including quantitative predictions matching experimental data.

Findings

The third virial coefficient varies rapidly across three-atom and atom-dimer thresholds.

The momentum distribution at unitarity exhibits a universal high-momentum tail with log-periodic dependence.

The lowest trimer state may not be occupied in current experiments.

Abstract

We compute the virial coefficients, the contact parameters, and the momentum distribution of a strongly interacting three-dimensional Bose gas by means of a virial expansion up to third order in the fugacity, which takes into account three-body correlations exactly. Our results characterize the nondegenerate regime of the interacting Bose gas, where the thermal wavelength is smaller than the interparticle spacing but the scattering length may be arbitrarily large. We observe a rapid variation of the third virial coefficient as the scattering length is tuned across the three-atom and the atom-dimer thresholds. The momentum distribution at unitarity displays a universal high-momentum tail with a log-periodic momentum dependence, which is a direct signature of Efimov physics. We provide a quantitative description of the momentum distribution at high momentum as measured by P. Makotyn et al. [Nat. Phys. 10, 116 (2014)], and our calculations indicate that the lowest trimer state might not be occupied in the experiment. Our results allow for a spectroscopy of Efimov states in the unitary limit.