BCS-BEC Crossover in Atomic Fermi Gases with a Narrow Resonance

TL;DR

This paper explores how the effective range of two-body interactions influences the BCS-BEC crossover in atomic Fermi gases, using a single-channel model with square well and barrier potentials to analyze scattering and pairing properties.

Contribution

It introduces a model incorporating effective range effects into the BCS-BEC crossover analysis, extending understanding beyond zero-range interactions.

Findings

Effective range significantly impacts the crossover behavior.

The model captures both positive and negative effective range effects.

Results provide insights into the momentum dependence of pairing and chemical potential.

Abstract

We determine the effects on the BCS-BEC crossover of the energy dependence of the effective two-body interaction, which at low energies is determined by the effective range. To describe interactions with an effective range of either sign, we consider a single-channel model with a two-body interaction having an attractive square well and a repulsive square barrier. We investigate the two-body scattering properties of the model, and then solve the Eagles-Leggett equations for the zero temperature crossover, determining the momentum dependent gap and the chemical potential self-consistently. From this we investigate the dependence of the crossover on the effective range of the interaction.