Topological superconductivity with deformable magnetic skyrmions

Maxime Garnier,Andrej Mesaros,Pascal Simon

doi:10.1038/s42005-019-0226-5

Abstract

Magnetic skyrmions are nanoscale spin configurations that are efficiently created and manipulated. They hold great promises for next-generation spintronics applications. In parallel, the interplay of magnetism, superconductivity and spin-orbit coupling has proved to be a versatile platform for engineering topological superconductivity predicted to host non-abelian excitations, Majorana zero modes. We show that topological superconductivity can be induced by proximitizing skyrmions and conventional superconductors, without need for additional ingredients. Apart from a previously reported Majorana zero mode in the core of the skyrmion, we find a more universal chiral band of Majorana modes on the edge of the skyrmion. We show that the chiral Majorana band is effectively flat in the physically relevant parameter regime, leading to interesting robustness and scaling properties. In particular, the number of Majorana modes in the (nearly-)flat band scales with the perimeter length of the system, while being robust to local disorder.

Highlights

Magnetic skyrmions are nanoscale spin configurations that are efficiently created and manipulated
We find here that a magnetic skyrmion of any azimuthal winding and sufficient radial winding gives rise to a single band of states at the edge of the skyrmion, i.e., a chiral Majorana edge mode (CMEM)
In summary, we have shown that a system composed of a magnetic skyrmion coupled to a conventional s-wave superconductor realizes a topological superconducting phase with a nearly dispersionless chiral Majorana mode at its edge

Summary

Introduction

Magnetic skyrmions are nanoscale spin configurations that are efficiently created and manipulated. The interplay of magnetism, superconductivity and spin-orbit coupling has proved to be a versatile platform for engineering topological superconductivity predicted to host non-abelian excitations, Majorana zero modes. Evidence that magnetic skyrmions can be driven by ultralow electric current densities[11,12] make them promising candidates for future spintronic applications[13] In parallel to these developments, the search for Majorana modes in condensed-matter systems has been the focus of great attention, motivated by their potential application in quantum computation. For the physically relevant range of parameters (skyrmion size, winding numbers, magnetic coupling strength) the CMEM has negligible velocity, i.e., it is nearly a Majorana flat band (MFB). Such deformations preserve the number of edge states proportional to the perimeter length of the edge

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Conclusion