Lifetime of the Bose Gas with Resonant Interactions

TL;DR

This paper investigates the lifetime of a Bose gas near unitarity using Feshbach resonance, revealing a temperature-dependent three-body decay law and continuity of decay rates across the resonance.

Contribution

The study provides the first detailed measurement of the temperature dependence of the three-body decay coefficient at unitarity and demonstrates its consistency with zero-range theory predictions.

Findings

The three-body decay coefficient $L_3$ follows a $1/T^2$ law at unitarity.

$L_3$ varies smoothly across the Feshbach resonance.

Experimental data agree with analytical zero-range theory calculations.

Abstract

We study the lifetime of a Bose gas at and around unitarity using a Feshbach resonance in lithium~7. At unitarity, we measure the temperature dependence of the three-body decay coefficient $L_{3}$. Our data follow a $L_3 {=} \lambda_{3} / T^{2}$ law with $\lambda_{3} = 2.5(3)_{stat}_(6)_{sys} 10^{-20} (\mu K)^2 cm^6 s^{-1}$ and are in good agreement with our analytical result based on the zero-range theory. Varying the scattering length $a$ at fixed temperature, we investigate the crossover between the finite-temperature unitary region and the previously studied regime where $|a|$ is smaller than the thermal wavelength. We find that $L_{3}$ is continuous across resonance, and over the whole $a {<} 0$ range our data quantitatively agree with our calculation.