Universal corrections to the superfluid gap in a cold Fermi gas

TL;DR

This paper develops a comprehensive effective field theory framework to compute superfluid gaps in cold Fermi gases, incorporating universal corrections that refine previous results and have implications for neutron star superfluidity.

Contribution

It introduces the complete set of subleading universal corrections to the superfluid gap within an EFT framework, extending beyond the well-known leading order results.

Findings

Universal corrections reduce the superfluid gap at low densities.

The framework reproduces the Gor'kov-Melik-Barkhudarov result at leading order.

Applications to neutron star superfluidity are discussed.

Abstract

A framework for computing the superfluid gap in an effective field theory (EFT) of fermions interacting via momentum-independent contact forces is developed. The leading universal corrections in the EFT are one-loop in-medium effects at the Fermi surface, and reproduce the well-known Gor'kov-Melik-Barkhudarov result. The complete subleading universal corrections are presented here, and include one-loop effects away from the Fermi surface, two-loop in-medium effects, as well as modifications to the fermion propagator. Together, these effects are found to reduce the gap at low densities. Applications to neutron superfluidity in neutron stars are also discussed.