Surface Energy in Cold Asymmetrical Fermion Superfluids

TL;DR

This paper derives the surface energy between normal and superfluid phases in a two-species fermion system, showing it influences phase stability mainly at strong coupling, with implications for understanding mixed phase energetics.

Contribution

It provides a detailed derivation of surface energy in asymmetric fermion superfluids and analyzes its impact on phase stability across coupling regimes.

Findings

Mixed phase remains favored at weak coupling.

Surface energy effects are significant only at strong coupling.

Surface energy influences phase stability in asymmetric fermion systems.

Abstract

We derive the energy of the surface between the normal and superfluid components of a mixed phase of a system composed of two particle species with different densities. The surface energy is obtained by the integration of the free energy density in the interface between the two phases. We show that the mixed phase remains as the favored ground state over the gapless phase in weak coupling. We find that the surface energy effects emerge only at strong coupling.