Oscillatory vortex interaction in a gapless fermion superfluid with spin population imbalance

TL;DR

This paper investigates the unconventional vortex interactions in a gapless fermion superfluid with spin imbalance, revealing an oscillatory attractive potential caused by gapless fermions, which influences vortex lattice behavior.

Contribution

It introduces a novel effective field theory analysis of vortex interactions in a gapless superfluid with spin imbalance, highlighting an oscillatory attractive potential similar to RKKY interactions.

Findings

Gapless fermions induce an oscillatory long-range attractive potential between vortices.

The interaction resembles the RKKY magnetic interaction in metals.

The vortex lattice structure may be affected by the competition between Coulomb repulsion and fermion-induced attraction.

Abstract

Using effective field theory approach we study a homogeneous superfluid state with a single (gapless) Fermi surface, recently suggested as a possible phase for an ultracold Fermi gas with spin-population imbalance. We find an unconventional form of the interaction between vortices. The presence of gapless fermions gives rise to an attractive long-range potential oscillating in space, analogous to the RKKY magnetic interaction in metals. Our study then leads to an interesting question as to the nature of the vortex lattice in the presence of competition between the usual repulsive logarithmic Coulomb and fermion-induced attractive oscillatory interactions.