Tests of universal three-body physics in an ultracold Bose-Fermi mixture

TL;DR

This study investigates whether the universality of three-body physics observed in homonuclear ultracold gases extends to heteronuclear mixtures, by measuring loss rates and Efimov resonances in a $^{40}$K-$^{87}$Rb mixture.

Contribution

First experimental exploration of Efimov physics in a heteronuclear Bose-Fermi mixture, revealing partial universality and new resonance behaviors.

Findings

Efimov-like resonance observed in molecule-atom collisions

No Efimov resonances detected in three-atom inelastic collisions

Results compared with previous heteronuclear experiments and theories

Abstract

Recent measurements of Efimov resonances in a number of ultracold atom species have revealed an unexpected universality, in which three-body scattering properties are determined by the van der Waals length of the two-body interaction potential. To investigate whether this universality extends to heteronuclear mixtures, we measure loss rate coefficients in an ultracold trapped gas of $^{40}$K and $^{87}$Rb atoms. We find an Efimov-like resonance in the rate of inelastic collisions between $^{40}$K$^{87}$Rb Feshbach molecules and $^{87}$Rb atoms. However, we do not observe any Efimov-related resonances in the rates of inelastic collisions between three atoms. These observations are compared to previous measurements by the LENS group of Efimov resonances in a $^{41}$K and $^{87}$Rb mixture as well as to recent predictions.