Majorana Edge States in Superconductor/Noncollinear Magnet Interfaces

TL;DR

This paper explores how interfacing superconductors with noncollinear magnetic insulators can induce unconventional pairing states that host Majorana edge modes, potentially enabling macroscopic quantum states without chemical potential tuning.

Contribution

It demonstrates that magnetic textures like cycloidal, helical, and skyrmion configurations induce novel pairing states supporting Majorana modes and persistent currents, expanding the understanding of topological superconductivity.

Findings

Induced ($p_{x}+p_{y}$)-wave pairing supports Majorana edge states.

Majorana states can be separated over macroscopic distances.

Skyrmion textures induce ($p_{r}+ip_{ heta}$)-wave states with persistent edge currents.

Abstract

Through $s-d$ coupling, a superconducting thin film interfaced to a noncollinear magnetic insulator inherits its magnetic order, which may induce unconventional superconductivity that hosts Majorana edge states. From the cycloidal, helical, or (tilted) conical magnetic order of multiferroics, or the Bloch and Neel domain walls of ferromagnetic insulators, the induced pairing is ($p_{x}+p_{y}$)-wave, a pairing state that supports Majorana edge modes without adjusting the chemical potential. In this setup, the Majorana states can be separated over the distance of the long range magnetic order, which may reach macroscopic scale. A skyrmion spin texture, on the other hand, induces a ($p_{r}+ip_{\varphi}$)-wave-like state, which albeit nonuniform and influenced by an emergent electromagnetic field, hosts both a bulk persistent current and a topological edge current.