Beyond universality in three-body recombination: an Effective Field Theory treatment

TL;DR

This paper extends the universal theory of three-body recombination to include finite effective range effects, revealing the need for an additional three-body parameter and improving the description of experimental data.

Contribution

It introduces a perturbative effective field theory approach that incorporates finite effective range corrections into three-body recombination analysis.

Findings

Finite effective range requires an extra three-body parameter for renormalization.

Range corrections improve the description of Lithium-7 recombination features.

Universal relations are extended but still conflict with some experimental data.

Abstract

We discuss the impact of a finite effective range on three-body systems interacting through a large two-body scattering length. By employing a perturbative analysis in an effective field theory well suited to this scale hierarchy we find that an additional three-body parameter is required for consistent renormalization once range corrections are considered. This allows us to extend previously discussed universal relations between different observables in the recombination of cold atoms to account for the presence of a finite effective range. We show that such range corrections allow us to simultaneously describe the positive and negative scattering-length loss features observed in recombination with Lithium-7 atoms by the Bar-Ilan group. They do not, however, significantly reduce the disagreement between the universal relations and the data of the Rice group on Lithium-7 recombination at positive and negative scattering lengths.