New class of topological superconductors protected by magnetic group symmetries

TL;DR

This paper introduces a new class of three-dimensional topological superconductors protected by magnetic group symmetries, enabling multiple Majorana zero modes to coexist at vortex ends, with potential realizations in specific materials.

Contribution

It identifies a novel magnetic symmetry that enhances topological classification, allowing for multiple Majorana modes at a single vortex in 3D superconductors.

Findings

Multiple MZMs can coexist at a vortex end due to enhanced topological classification.

A vortex binding two MZMs can be realized in SnTe with proximity-induced pairing.

The new symmetry extends the classification from Z_2 to Z, indicating richer topological phases.

Abstract

We study a new type of three-dimensional topological superconductors that exhibit Majorana zero modes (MZM) protected by a magnetic group symmetry, a combined antiunitary symmetry composed of a mirror reflection and time-reversal. This new symmetry enhances the noninteracting topological classification of a superconducting vortex from $Z_2$ to $Z$, indicating that multiple MZMs can coexist at the end of one magnetic vortex of unit flux. Specially, we show that a vortex binding two MZMs can be realized on the $(001)$-surface of a topological crystalline insulator SnTe with proximity induced BCS Cooper pairing, or in bulk superconductor In$_x$Sn$_{1-x}$Te.