Topological multiband s-wave superconductivity in coupled multifold fermions

TL;DR

This paper investigates topological superconductivity in noncentrosymmetric materials with coupled multifold nodes, revealing conditions under which a topological phase with Majorana surface states can emerge.

Contribution

It introduces a model for topological superconductivity in RhSi and similar materials, highlighting the role of coupled multifold nodes and the $s_{+} igoplus s_{-}$ gap function.

Findings

Topological superconductivity supports Majorana cones and nodal rings.

The phase is favored over a wide range of interaction parameters.

Coupled multifold nodes are key to the topological phase stability.

Abstract

We study three-dimensional time-reversal-invariant topological superconductivity in noncentrosymmetric materials such as RhSi, CoSi, and AlPt which host coupled multifold nodes energetically split by the spin-orbit coupling at the same time-reversal-invariant momentum (TRIM). The topological superconductivity arises from the $s_{+} \oplus s_{-}$ gap function, which is $\boldsymbol{k}$ independent, but with opposite signs for the two nodes split at the same TRIM. We consider various electron-electron interactions in the tight-binding model for RhSi and find that the topological superconducting phase supporting a surface Majorana cone and topological nodal rings is favored in a wide range of interaction parameters.