From Narrow to Broad Feshbach Resonances: Condensate Fraction of Cooper Pairs and Preformed Molecules

TL;DR

This paper investigates fermionic condensation across narrow and broad Feshbach resonances using a two-channel model, analyzing how atom-molecule coupling and scattering length influence condensate properties and the roles of Cooper pairs and preformed molecules.

Contribution

It extends previous work to include narrow Feshbach resonances and analyzes the condensate fraction contributions during two different crossovers.

Findings

Predicted the contribution of Cooper pairs and preformed molecules to the condensate density.

Analyzed the effects of atom-molecule coupling and scattering length on key properties.

Provided insights into the BCS-BEC crossover and narrow to broad resonance transition.

Abstract

We extend our previous investigations of fermionic condensation in broad Feshbach resonances by using the two-channel model developed for narrow Feshbach resonances. We investigate two crossovers: the BCS-BEC crossover by changing the s-wave scattering length and the crossover from a narrow to a broad resonance by changing the atom-molecule coupling. At zero temperature we analyze, as a function of both atom-molecule coupling and s-wave scattering length, the chemical potential, the energy gap, and the condensate fraction of atoms. In particular, we predict the contribution of Cooper pairs and preformed molecules to the total condensate density along the two crossovers.