Topological surface superconductivity in doped Weyl loop materials

TL;DR

This paper explores topological surface superconductivity in doped Weyl loop materials, revealing novel Majorana modes and flat bands that emerge from the interplay of bulk and surface states, offering new avenues for topological quantum states.

Contribution

It demonstrates that doped Weyl loop materials can host topological surface superconductivity with Majorana modes, even in strong pairing regimes, expanding the understanding of topological phases.

Findings

Surface superconductivity is topological with Majorana modes at vortices.

Majorana zero modes appear even in strong pairing regimes.

Surface hosts a flat band of charge neutral Majorana fermions.

Abstract

We study surface superconductivity involving the `drumhead' surface states of (doped) Weyl loop materials. The leading weak coupling instability in the bulk is toward a chiral superconducting order, which fully gaps the Fermi surface. In this state the surface also becomes superconducting, with $p+ip$ symmetry. We show that the surface SC state is "topological" as long as it is fully gapped, and the system traps Majoarana modes wherever a vortex line enters or exits the bulk. In contrast to true 2D $p+ip$ superconductors, these Majorana zero modes arise even in the "strong pairing" regime where the chemical potential is entirely above/below the drumhead. We also consider conventional $s$-wave pairing, and show that in this case the surface hosts a flat band of charge neutral Majorana fermions, whose momentum range is given by the projection of the bulk Fermi surface. Weyl loop materials thus provide access to new forms of topological superconductivity.