Universal Dimer in a Collisionally Opaque Medium: Experimental Observables and Efimov Resonances

TL;DR

This paper investigates how secondary collisions of universal dimers in ultracold atomic gases affect the interpretation of Efimov resonances, revealing that maximum secondary collisions do not always indicate Efimov resonances, thus clarifying experimental controversies.

Contribution

It demonstrates that in collisionally opaque media, the maximum secondary collisions do not necessarily correspond to Efimov resonances, highlighting the importance of finite range corrections.

Findings

Maximum secondary collisions can occur away from Efimov resonances.

Finite range effects significantly influence Efimov energy levels.

Experimental interpretations of Efimov resonances need to consider collision opacity.

Abstract

A universal dimer is subject to secondary collisions with atoms when formed in a cloud of ultracold atoms via three-body recombination. We show that in a collisionally opaque medium, the value of the scattering length that results in the maximum number of secondary collisions may not correspond to the Efimov resonance at the atom-dimer threshold and thus can not be automatically associated with it. This result explains a number of controversies in recent experimental results on universal three-body states and supports the emerging evidence for the significant finite range corrections to the first excited Efimov energy level.