Observation of heteronuclear atomic Efimov resonances

TL;DR

This paper reports the first experimental observation of Efimov resonances in a heteronuclear atomic mixture, demonstrating three-body collision enhancements linked to Efimov trimers in a K-Rb system.

Contribution

It provides the first experimental evidence of heteronuclear Efimov resonances using ultracold $^{41}$K and $^{87}$Rb atoms and broad Feshbach resonances.

Findings

Observation of three distinct three-body collision enhancements

Identification of Efimov trimers KKRb and KRbRb

Evidence of Efimov physics in heteronuclear systems

Abstract

The Efimov effect represents a cornerstone in few-body physics. Building on the recent experimental observation with ultracold atoms, we report the first experimental signature of Efimov physics in a heteronuclear system. A mixture of $^{41}$K and $^{87}$Rb atoms was cooled to few hundred nanoKelvins and stored in an optical dipole trap. Exploiting a broad interspecies Feshbach resonance, the losses due to three-body collisions were studied as a function of the interspecies scattering length. We observe an enhancement of the three-body collisions for three distinct values of the interspecies scattering lengths, both positive and negative. We attribute the two features at negative scattering length to the existence of two kind of Efimov trimers, namely KKRb and KRbRb.