Chirality-driven orbital magnetic moments as a new probe for topological magnetic structures

TL;DR

This paper investigates how topological magnetic structures like skyrmions induce orbital magnetic moments driven by emergent magnetic fields, proposing a new spectroscopic method for their identification.

Contribution

It demonstrates that the topological orbital magnetism in skyrmions is a robust, deformation-invariant property, and introduces a first-principles approach to characterize it.

Findings

Orbital magnetic moments in skyrmions are topologically protected.

Emergent magnetic fields lead to a topological contribution to orbital magnetism.

Proposed a soft x-ray spectroscopy protocol to identify topological magnetic structures.

Abstract

When electrons are driven through unconventional magnetic structures, such as skyrmions, they experience emergent electromagnetic fields that originate several Hall effects. Independently, ground state emergent magnetic fields can also lead to orbital magnetism, even without the spin-orbit interaction. The close parallel between the geometric theories of the Hall effects and of the orbital magnetization raises the question: does a skyrmion display topological orbital magnetism? Here we first address the smallest systems with nonvanishing emergent magnetic field, trimers, characterizing the orbital magnetic properties from first-principles. Armed with this understanding, we study the orbital magnetism of skyrmions, and demonstrate that the contribution driven by the emergent magnetic field is topological. This means that the topological contribution to the orbital moment does not change under continous deformations of the magnetic structure. Furthermore, we use it to propose a new experimental protocol for the identification of topological magnetic structures, by soft x-ray spectroscopy.