DIII Topological Superconductivity with Emergent Time-Reversal Symmetry

TL;DR

This paper introduces a new class of topological superconductors with an emergent time-reversal symmetry that appears only in an effective low-dimensional model, enabling realization of class DIII phases under specific conditions.

Contribution

It demonstrates that class DIII topological superconductivity can occur in noninteracting systems coupled to s-wave superconductors even when physical time-reversal symmetry is broken, with explicit criteria and models.

Findings

Realization of class DIII topological phase in 1D models

Emergent time-reversal symmetry protects Majorana Kramers pairs

Conditions for achieving topological phases with broken physical TR symmetry

Abstract

We find a new class of topological superconductors which possess an emergent time-reversal symmetry that is present only after projecting to an effective low-dimensional model. We show that a topological phase in symmetry class DIII can be realized in a noninteracting system coupled to an $s$-wave superconductor only if the physical time-reversal symmetry of the system is broken, and we provide three general criteria that must be satisfied in order to have such a phase. We also provide an explicit model which realizes the class DIII topological superconductor in 1D. We show that, just as in time-reversal invariant topological superconductors, the topological phase is characterized by a Kramers pair of Majorana fermions that are protected by the emergent time-reversal symmetry.