Shallow Efimov tetramer as inelastic virtual state and resonant enhancement of the atom-trimer relaxation

TL;DR

This paper reveals that shallow Efimov tetramers are inelastic virtual states rather than unstable bound states, causing resonant atom-trimer scattering and enhanced relaxation in ultracold gases, challenging previous predictions.

Contribution

It demonstrates that shallow Efimov tetramers can be inelastic virtual states, not unstable bound states, affecting atom-trimer interactions in ultracold systems.

Findings

Shallow Efimov tetramers are inelastic virtual states.

Resonant enhancement of atom-trimer relaxation observed.

Contradicts previous predictions of unstable bound states.

Abstract

We use exact four-boson scattering equations in the momentum-space framework to study the universal properties of shallow Efimov tetramers and their dependence on the two-boson scattering length. We demonstrate that, in contrast to previous predictions, the shallow tetramer in a particular experimentally unexplored regime is not an unstable bound state but an inelastic virtual state. This leads to a resonant behaviour of the atom-trimer scattering length and thereby to a resonant enhancement of the trimer relaxation in ultracold atom-trimer mixtures.