Higher-order topological superconductor phases in a multilayer system

TL;DR

This paper explores multilayer topological insulator/superconductor systems under Zeeman coupling, revealing three distinct higher-order topological superconductor phases with unique Majorana modes and surface states.

Contribution

It introduces a new multilayer system model to realize various higher-order topological superconductor phases with distinct Majorana modes.

Findings

Identified a second-order topological superconductor with Majorana hinge flat bands.

Discovered a second-order Dirac superconductor with surface Majorana cones.

Found nodal-line superconductor phases with drumhead surface states.

Abstract

Higher-order topological phases are gapped phases of matter that host gapless corner or hinge modes. For the case of superconductors, corner or hinge modes are gapless Majorana modes or Majorana zero modes. To construct 3d higher-order topological superconductors, we consider a topological-insulator/superconductor multilayer under in-plane Zeeman coupling. We found three different types of higher-order topological superconductor phases, a second-order topological superconductor phase with Majorana hinge flat bands, a second-order Dirac superconductor phase with surface Majorana cones and Majorana hinge arcs, and nodal-line superconductor phases with drumhead surface states and Majorana hinge arcs.