Chiral Majorana Hinge Modes in Superconducting Dirac Materials

TL;DR

This paper explores the emergence of chiral Majorana hinge modes in three-dimensional second-order topological superconductors within Dirac materials, highlighting the role of specific pairing symmetries and crystalline properties.

Contribution

It identifies s+id-wave pairing as a topologically nontrivial state capable of hosting Majorana hinge modes in Dirac materials, without external fields.

Findings

s+id-wave pairing leads to topological superconductivity

Majorana hinge modes characterized by quadrupole moment winding number

Strong spin-orbital coupling and crystalline symmetries facilitate realization

Abstract

Chiral Majorana hinge modes are characteristic of a second-order topological superconductor in three dimensions. Here we systematically study pairing symmetry in the point group D_{2h}, and find that the leading pairing channels can be of s-, d-, and s+id-wave pairing in Dirac materials. Except for the odd-parity s-wave pairing superconductivity, the s+id-wave pairing superconductor is topologically nontrivial and possesses Majorana hinge and surface modes. The chiral Majorana hinge modes can be characterized by a winding number of the quadrupole moment, or quantized quadruple moment at the symmetrically invariant point. Our findings suggest the strong spin-orbital coupling, crystalline symmetries and electron-electron interaction in the Dirac materials may provide a microscopic mechanism to realize chiral Majorana hinge modes without utilizing the proximity effect or external fields.