Majorana Edge States in Superconductor/Noncollinear Magnet Interfaces

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.