Nested Defects on the Boundary of Topological Superconductors

TL;DR

This paper investigates how nested defects in the Zeeman field on the boundary of 3D topological superconductors can induce dimensional reduction of Majorana edge states, revealing new localization phenomena and generalizing index theorems.

Contribution

It introduces the concept of nested defect configurations affecting Majorana modes and generalizes the index theorem for topological interfaces.

Findings

Dimensional reduction of Majorana modes from 2D to 1D or 0D at magnetic domain walls.

Localization of Majorana modes depends on Zeeman field magnitude and configuration.

Generalization of the index theorem for systems with partial Chern numbers.

Abstract

Helical Majorana edge states at the 2D boundaries of 3D topological superconductors can be gapped by a surface Zeeman field. Here we study the effect nested defects imprinted on the Zeeman field can have on the edge states. We demonstrate that depending on the configuration of the field we can induce dimensional reduction of gapless Majorana modes from 2D to 1D or quasi-0D at magnetic domain walls. We determine the nature of the Majorana localisation on these defects as a function of the magnitude and configuration of the Zeeman field. Finally, we observe a generalisation of the index theorem governing the number of gapless modes at the interface between topologically non-trivial systems with partial Chern numbers.