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

TL;DR

This paper investigates the interplay between BCS pairing and molecular states in dense ultracold Fermi gases near Feshbach resonance, revealing a lower bound for molecular binding energy that signals the BCS phase.

Contribution

It introduces a new understanding of the molecular binding energy threshold in relation to the BCS phase in ultracold Fermi gases.

Findings

Existence of a non-zero lower bound for molecular binding energy in the BCS phase

Potential experimental method to detect BCS phase via molecular binding energy

Analysis within a recent many-body theoretical framework

Abstract

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