Topological magnon band structure of emergent Landau levels in a skyrmion lattice

TL;DR

This paper demonstrates the existence of topological magnon band structures in a skyrmion lattice, revealing emergent Landau levels and nontrivial topology through neutron scattering experiments.

Contribution

It provides experimental evidence of topological magnon bands and emergent Landau levels in a skyrmion lattice, linking real-space topology to reciprocal space phenomena.

Findings

Observation of emergent Landau levels in magnon spectra

Evidence of topological magnon band structure

Magnon behavior consistent with fictitious magnetic fields

Abstract

The motion of a spin excitation across topologically non-trivial magnetic order exhibits a deflection that is analogous to the effect of the Lorentz force on an electrically charged particle in an orbital magnetic field. We used polarized inelastic neutron scattering to investigate the propagation of magnons (i.e., bosonic collective spin excitations) in a lattice of skyrmion tubes in manganese silicide. For wave vectors perpendicular to the skyrmion tubes, the magnon spectra are consistent with the formation of finely spaced emergent Landau levels that are characteristic of the fictitious magnetic field used to account for the nontrivial topological winding of the skyrmion lattice. This provides evidence of a topological magnon band structure in reciprocal space, which is borne out of the nontrivial real-space topology of a magnetic order.