Topological septet pairing with spin-$\frac{3}{2}$ fermions -- high partial-wave channel counterpart of the $^3$He-B phase

TL;DR

This paper extends the topologically non-trivial $^3$He-B phase to higher partial-wave channels in multi-component fermions, revealing new topological phases with complex surface spectra and potential applications in condensed matter and cold atom systems.

Contribution

It introduces a systematic generalization of the $^3$He-B phase to arbitrary partial-wave channels for multi-component fermions, highlighting topological properties and surface states.

Findings

Odd partial-wave pairings are topologically non-trivial.

Surface spectra show multiple linear and high-order Dirac cones.

Topological index reaches $N^2$ in the p-wave channel.

Abstract

We systematically generalize the exotic $^3$He-B phase, which not only exhibits unconventional symmetry but is also isotropic and topologically non-trivial, to arbitrary partial-wave channels with multi-component fermions. The concrete example with four-component fermions is illustrated including the isotropic $f$, $p$ and $d$-wave pairings in the spin septet, triplet, and quintet channels, respectively. The odd partial-wave channel pairings are topologically non-trivial, while pairings in even partial-wave channels are topologically trivial. The topological index reaches the largest value of $N^2$ in the $p$-wave channel ($N$ is half of the fermion component number). The surface spectra exhibit multiple linear and even high order Dirac cones. Applications to multi-orbital condensed matter systems and multi-component ultra-cold large spin fermion systems are discussed.