Topological Phase Transitions and a Two-Dimensional Weyl Superconductor in a Half-Metal/Superconductor Heterostructure

TL;DR

This paper explores topological phase transitions in a half-metal/superconductor heterostructure, revealing new phases including a 2D Weyl superconductor with unique edge states, driven by magnetization orientation tuning.

Contribution

It introduces the discovery of multiple topological phase transitions and identifies the topological invariants and symmetries protecting the 2D Weyl superconductor phase.

Findings

Transitions between gapped and gapless topological phases

Change from counter-propagating to unidirectional Majorana edge modes

Identification of a 2D Weyl superconductor with Fermi line edge states

Abstract

We find a series of topological phase transitions in a half-metal/superconductor heterostructure, by tuning the direction of the magnetization of the half-metal film. These include transitions between a topological superconducting phase with a bulk gap and another phase without a bulk gap but has a ubiquitous local gap. At the same time, the edge states change from counter-propagating Majorana edge modes to unidirectional Majorana edge modes. In addition, we find transitions between the second phase and a nodal phase which turns out to be a two-dimensional Weyl superconductor with Fermi line edge states. We identify the topological invariants relevant to each phase and the symmetry that protects the Weyl superconductivity phase.