Self-Organized Topological Superconductivity in a Yu-Shiba-Rusinov Chain

TL;DR

This paper investigates how magnetic chains on superconductors can self-organize into topological superconducting states with Majorana modes, driven by interactions mediated through Yu-Shiba-Rusinov states, revealing a transition from simple spin models to complex topological phases.

Contribution

It demonstrates the emergence of topological superconductivity in magnetic chains due to Yu-Shiba-Rusinov states, highlighting a transition from collinear to spiral magnetic order and the stabilization of p-wave gaps.

Findings

Spiral magnetic order forms in superconducting phase.

Strong spin-spin interactions mediated by Yu-Shiba-Rusinov states.

Potential realization of topological superconductivity with Majorana modes.

Abstract

We study a chain of magnetic moments exchange coupled to a conventional three dimensional superconductor. In the normal state the chain orders into a collinear configuration, while in the superconducting phase we find that ferromagnetism is unstable to the formation of a magnetic spiral state. Beyond weak exchange coupling the spiral wavevector greatly exceeds the inverse superconducting coherence length as a result of the strong spin-spin interaction mediated through the subgap band of Yu-Shiba-Rusinov states. Moreover, the simple spin-spin exchange description breaks down as the subgap band crosses the Fermi energy, wherein the spiral phase becomes stabilized by the spontaneous opening of a $p-$wave superconducting gap within the band. This leads to the possibility of electron-driven topological superconductivity with Majorana boundary modes using magnetic atoms on superconducting surfaces.