Temperature dependence of an Efimov resonance in $^{39}\mathrm{K}$

TL;DR

This study investigates how an Efimov resonance in ultracold $^{39}$K shifts with temperature, revealing a decrease in resonance prominence at lower temperatures and estimating the zero-temperature three-body parameter.

Contribution

It provides the first detailed analysis of temperature effects on Efimov resonances in $^{39}$K, including empirical and theoretical modeling and new experimental insights.

Findings

Resonance position shifts to lower scattering lengths at lower temperatures

Resonance becomes less prominent as temperature decreases

Estimated zero-temperature three-body parameter

Abstract

Ultracold atomic gases are an important testing ground for understanding few-body physics. In particular, these systems enable a detailed study of the Efimov effect. We use ultracold $^{39}\mathrm{K}$ to investigate the temperature dependence of an Efimov resonance. The shape and position of the observed resonance are analyzed by employing an empirical fit, and universal finite-temperature zero-range theory. Both procedures suggest that the resonance position shifts towards lower absolute scattering lengths when approaching the zero-temperature limit. We extrapolate this shift to obtain an estimate of the three-body parameter at zero temperature. A surprising finding of our study is that the resonance becomes less prominent at lower temperatures, which currently lacks a theoretical description and implies physical effects beyond available models. Finally, we present measurements performed near the Feshbach resonance center and discuss the prospects for observing the second Efimov resonance in $^{39}\mathrm{K}$.