Universal Loss Dynamics in a Unitary Bose Gas

TL;DR

This paper presents a theoretical and experimental study of loss dynamics in a unitary Bose gas, revealing a universal trap condition where cooling balances heating, and measures the Efimov inelasticity parameter for the first time.

Contribution

The work introduces a universal model for loss dynamics in a unitary Bose gas and provides the first measurement of the Efimov inelasticity parameter in this context.

Findings

Identification of a universal trap depth balancing cooling and heating.

Experimental validation with Cs and Li atoms supports the model.

First measurement of Efimov inelasticity parameter η* in 133 Cs.

Abstract

The low temperature unitary Bose gas is a fundamental paradigm in few-body and many-body physics, attracting wide theoretical and experimental interest. Here we first present a theoretical model that describes the dynamic competition between two-body evaporation and three-body re-combination in a harmonically trapped unitary atomic gas above the condensation temperature. We identify a universal magic trap depth where, within some parameter range, evaporative cooling is balanced by recombination heating and the gas temperature stays constant. Our model is developed for the usual three-dimensional evaporation regime as well as the 2D evaporation case. Experiments performed with unitary 133 Cs and 7 Li atoms fully support our predictions and enable quantitative measurements of the 3-body recombination rate in the low temperature domain. In particular, we measure for the first time the Efimov inelasticity parameter $\eta$ * = 0.098(7) for the 47.8-G d-wave Feshbach resonance in 133 Cs. Combined 133 Cs and 7 Li experimental data allow investigations of loss dynamics over two orders of magnitude in temperature and four orders of magnitude in three-body loss. We confirm the 1/T 2 temperature universality law up to the constant $\eta$ *.