Interior Gap Superfluidity

TL;DR

This paper introduces a novel state called interior gap superfluidity where a system exhibits both superfluid and normal metallic properties simultaneously, characterized by a gap within the Fermi surface and gapless exterior.

Contribution

It proposes the concept of interior gap superfluidity, a new phase of matter that combines superfluid and metallic behaviors, realizable in cold atomic mixtures and certain solid materials.

Findings

Predicts realization in cold fermionic atom mixtures with different masses.

Describes a state with coexisting gapped and gapless quasiparticles.

Suggests potential existence in specific electronic materials.

Abstract

We propose a new state of matter in which the pairing interactions carve out a gap within the interior of a large Fermi ball, while the exterior surface remains gapless. This defines a system which contains both a superfluid and a normal Fermi liquid simultaneously, with both gapped and gapless quasiparticle excitations. This state can be realized at weak coupling. We predict that a cold mixture of two species of fermionic atoms with different mass will exhibit this state. For electrons in appropriate solids, it would define a material that is simultaneously superconducting and metallic.