Majorana Fermions in Nodal Superconductors: Gapless Topological Phase

TL;DR

This paper shows that Majorana fermions can exist in the edges and vortex cores of nodal superconductors like d-wave pairing states under certain conditions, expanding potential systems for exploring Majorana states.

Contribution

It demonstrates the existence of topologically protected Majorana fermions in nodal superconductors with gapless excitations, under realistic conditions involving spin-orbit interaction and magnetic field.

Findings

Majorana fermions exist in edges and vortex cores of nodal superconductors.

Majorana states are topologically protected despite bulk gapless excitations.

Expands the class of systems where Majorana fermions can be realized.

Abstract

We demonstrate that Majorana fermions exist in edges of systems and in a vortex core even for superconductors with nodal excitations such as the d-wave pairing state under a particular but realistic condition in the case with an anti-symmetric spin-orbit interaction and a nonzero magnetic field below the upper critical field. We clarify that the Majorana fermion state is topologically protected in spite of the presence of bulk gapless nodal excitations, because of the existence of a nontrivial topological number. Our finding drastically enlarges target systems where we can explore the Majorana fermion state.