Threshold of molecular bound state and BCS transition in dense ultracold Fermi gases with Feshbach resonance

摘要

We consider the normal state of a dense ultracold atomic Fermi gas in thepresence of a Feshbach resonance. We study the BCS and the molecularinstabilities and their interplay, within the framework of a recent many-bodyapproach. We find surprisingly that, in the temperature domain where the BCSphase is present, there is a non zero lower bound for the binding energy ofmolecules at rest. This could give an experimental mean to show the existenceof the BCS phase without observing it directly.