Hinge Majorana Flat Band in Type-II Dirac Semimetals

TL;DR

This paper predicts a new topological superconducting state in Type-II Dirac semimetals, featuring coexisting first- and second-order Majorana modes, driven by inter-orbital attraction and robust against symmetry-breaking.

Contribution

It introduces a novel inter-orbital superconducting state with coexisting topological phases and robust hinge Majorana flat bands in Type-II Dirac semimetals.

Findings

Presence of surface helical Majorana cones

Hinge Majorana flat bands across the hinge Brillouin zone

Higher-order hinge modes are symmetry-breaking robust

Abstract

Type-II Dirac semimetals exhibit a unique Fermi surface topology, which allows them to host novel topological superconductivity (TSC). We reveal a novel inter-orbital superconducting state, corresponding to the B1u and B2u pairings under the D4h point group. Intriguingly, we find that both first- and second-order TSC coexist in this novel state. It is induced by a dominant inter-orbital attraction and possesses surface helical Majorana cones and hinge Majorana flat bands, spanning the entire z-directed hinge Brillouin zone. Further investigation uncovers that these higher-order hinge modes are robust against the C4z symmetry-breaking perturbation.