On the Nature of Feshbach Resonances

R. Combescot

We propose a coherent framework allowing one to treat many-body effects in dense ultracold Fermi gases in the presence of a Feshbach resonance. We show that the simple effect of Pauli exclusion induces a strong modification of the basic scattering properties. In particular, this washes out the Feshbach resonance and provides a natural explanation for recent experimental findings.

Hélène Lefebvre-Brion, Annick Giusti-Suzor

Kajsa-My Tempest, S. Jonsell

Because Feshbach resonances can be used to tune atom-atom scattering, they are used as a tool to study Efimov physics in three-body ultracold systems. Here the authors develop and test a model that explicitly includes the multichannel nature of the physics near a Feshbach resonance, and find that the model captures features that are missed by the typical single-channel model.

Yoji Ohashi

We discuss the superfluid phase transition in a gas of Fermi atoms with a Feshbach resonance. A tunable pairing interaction associated with the Feshbach resonance is shown to naturally lead to the BCS-BEC crossover, where the character of superfluidity continuously changes from the weak-coupling Bardeen-Cooper-Schrieffer (BCS) type to the Bose-Einstein condensation (BEC) of tightly bound molecules, as one decreases the threshold energy 2ν of the Feshbach resonance. We also discuss effects of a trap, as well as the p-wave BCS-BEC crossover adjusted by a p-wave Feshbach resonance.