Grain-boundary topological superconductor

TL;DR

This paper proposes that grain boundary defects in two-dimensional topological superconductors can host Majorana zero modes, which are promising for quantum computing, with their existence controlled by magnetic fields.

Contribution

It introduces a novel mechanism where grain boundary defects host topological superconductivity with Majorana modes, driven by magnetic-field-induced hybridization of localized states.

Findings

Grain boundaries can host topological superconductivity with Majorana zero modes.

The emergence of these modes depends on the magnetic field's angle and magnitude.

Numerical and analytical methods confirm the defect-hosted Majorana modes in specific conditions.

Abstract

Majorana zero modes (MZMs) are of central importance for modern condensed matter physics and quantum information due their non-Abelian nature, which thereby offers the possibility of realizing topological quantum bits. We here show that a grain boundary (GB) defect can host a topological superconductor (SC), with a pair of cohabitating MZMs at its end when immersed in a parent two-dimensional gapped topological SC with the Fermi surface enclosing a nonzero momentum. The essence of our proposal lies in the magnetic-field driven hybridization of the localized MZMs at the elementary blocks of the GB defect, the single lattice dislocations, due to the MZM spin being locked to the Burgers vector. Indeed, as we show through numerical and analytical calculations, the GB topological SC with two localized MZMs emerges in a finite range of both the angle and magnitude of the external magnetic field. Our work demonstrates the possibility of defect-based platforms for quantum information technology and opens up a route for their systematic search in future.