Pairing in Asymmetrical Fermi Systems with Intra- and Inter-Species Correlations

TL;DR

This paper investigates pairing mechanisms in asymmetrical Fermi systems with intra- and inter-species interactions, revealing phase behaviors and superfluid states across BCS-BEC regimes relevant to ultracold atoms, nuclear, and quark matter.

Contribution

It introduces a coupled mean-field framework for intra- and inter-species pairing, constructing a phase diagram that accounts for finite polarization effects and phase separations.

Findings

BCS singlet superfluid can sustain finite polarization due to intra-species correlations

Phase separation occurs at larger polarizations in both BCS and BEC regimes

Superfluid phase persists for all polarizations deep in BEC regime

Abstract

We consider inter- and intra-species pairing interactions in an asymmetrical Fermi system. Using equation of motion method, we obtain coupled mean-field equations for superfluid gap functions and population densities. We construct a phase diagram across BCS-BEC regimes. Due to intra-species correlations, the BCS singlet superfluid state can sustain finite polarizations, $P$. For larger $P$, we find phase separations in BCS and BEC regimes. A superfluid phase exists for all $P$ deep in BEC regime. Our results may apply to pairing in ultracold fermions, nuclear and quark matter physics.