Observation of an Efimov-like resonance in ultracold atom-dimer scattering

TL;DR

This paper reports the observation of an Efimov-like resonance in ultracold atom-dimer scattering, providing experimental evidence for universal three-body phenomena in a controlled quantum system.

Contribution

First experimental observation of an atom-dimer Efimov resonance in ultracold caesium gases, linking few-body physics to universal Efimov states.

Findings

Detected an atom-dimer scattering resonance.

Interpreted the resonance as a trimer state hitting the atom-dimer threshold.

Discussed the resonance's relation to Efimov's scenario.

Abstract

The field of few-body physics has originally been motivated by understanding nuclear matter. New model systems to experimentally explore few-body quantum systems can now be realized in ultracold gases with tunable interactions. Albeit the vastly different energy regimes of ultracold and nuclear matter (peV as compared to MeV), few-body phenomena are universal for near-resonant two-body interactions. Efimov states represent a paradigm for universal three-body states, and evidence for their existence has been obtained in measurements of three-body recombination in an ultracold gas of caesium atoms. Interacting samples of halo dimers can provide further information on universal few-body phenomena. Here we study interactions in an optically trapped mixture of such halo dimers with atoms, realized in a caesium gas at nanokelvin temperatures. We observe an atom-dimer scattering resonance, which we interpret as being due to a trimer state hitting the atom-dimer threshold. We discuss the close relation of this observation to Efimov's scenario, and in particular to atom-dimer Efimov resonances.