Local-field Theory of the BCS-BEC Crossover

TL;DR

This paper presents a comprehensive self-consistent local-field theory that unifies the description of the BCS-BEC crossover in quantum Fermi gases, incorporating fluctuations beyond mean field and applicable to experimental cold atom systems.

Contribution

It introduces a novel theoretical framework that covers the entire BCS-BEC phase diagram, including regimes difficult for quantum Monte Carlo methods, and accounts for fluctuation effects.

Findings

Unified description of BCS-BEC crossover

Includes fluctuations beyond mean field

Applicable to narrow and broad Fano-Feshbach resonances

Abstract

We develop a self-consistent theory unifying the description of a quantum Fermi gas in the presence of a Fano-Feshbach resonance in the whole phase diagram ranging from BCS to BEC type of superfluidity and from narrow to broad resonances, including the fluctuations beyond mean field. Our theory covers a part of the phase diagram which is not easily accessible by Quantum Monte Carlo simulations and is becoming interesting for a new class of experiments in cold atoms.