Atom Loss Resonances in a Bose-Einstein Condensate

TL;DR

This paper introduces a new mechanism explaining atom loss resonances in Bose-Einstein condensates, involving coherent dimer formation during scattering length ramps, and predicts narrow loss enhancements near specific resonances.

Contribution

It proposes a novel theoretical model linking atom-dimer and dimer-dimer resonances to coherent dimer formation in BECs, supported by effective field theory.

Findings

Predicts narrow atom loss rate enhancements near resonances

Describes atom and dimer condensates with a universal effective field theory

Matches theoretical predictions with known few-body physics results

Abstract

Atom loss resonances in ultracold trapped atoms have been observed at scattering lengths near atom-dimer resonances, at which Efimov trimers cross the atom-dimer threshold, and near two-dimer resonances, at which universal tetramers cross the dimer-dimer threshold. We propose a new mechanism for these loss resonances in a Bose-Einstein condensate of atoms. As the scattering length is ramped to the large final value at which the atom loss rate is measured, the time-dependent scattering length generates a small condensate of shallow dimers coherently from the atom condensate. The coexisting atom and dimer condensates can be described by a low-energy effective field theory with universal coefficients that are determined by matching exact results from few-body physics. The classical field equations for the atom and dimer condensates predict narrow enhancements in the atom loss rate near atom-dimer resonances and near two-dimer resonances due to inelastic dimer collisions.