The J-triplet Cooper pairing with magnetic dipolar interactions

TL;DR

This paper explores a novel orbital p-wave spin triplet pairing mechanism in magnetic dipolar Fermi gases, highlighting its unique symmetry properties and differences from known superfluid phases.

Contribution

It introduces a new pairing symmetry in magnetic dipolar Fermi gases, emphasizing the role of quantum-mechanical spin operators and isotropy under spin-orbit rotation.

Findings

Proposes a robust p-wave spin triplet pairing with total angular momentum J=1.

Differentiates this pairing from $^3$He superfluid phases and electric dipolar systems.

Highlights the isotropic nature of unpolarized magnetic dipolar gases under combined spin-orbit rotation.

Abstract

Recently, cold atomic Fermi gases with the large magnetic dipolar interaction have been laser cooled down to quantum degeneracy. Different from electric-dipoles which are classic vectors, atomic magnetic dipoles are quantum-mechanical matrix operators proportional to the hyperfine-spin of atoms, thus provide rich opportunities to investigate exotic many-body physics. Furthermore, unlike anisotropic electric dipolar gases, unpolarized magnetic dipolar systems are isotropic under simultaneous spin-orbit rotation. These features give rise to a robust mechanism for a novel pairing symmetry: orbital p-wave (L=1) spin triplet (S=1) pairing with total angular momentum of the Cooper pair J=1. This pairing is markedly different from both the $^3$He-B phase in which J=0 and the $^3$He-$A$ phase in which $J$ is not conserved. It is also different from the p-wave pairing in the single-component electric dipolar systems in which the spin degree of freedom is frozen.