Tunable skyrmion crystals and topological quantum oscillations in magnetic metals

TL;DR

This paper investigates tunable skyrmion crystal phases in magnetic metals, revealing how their properties can be controlled by magnetic fields, leading to observable topological quantum oscillations in electronic states.

Contribution

It introduces a model showing how non-linear mode coupling extends skyrmion stability and enables field-tunable lattice constants, resulting in a new realization of Berry-Hofstadter phenomena.

Findings

Skyrmion crystal stability range is extended by non-linear mode coupling.

Lattice constant of skyrmion crystals can be tuned by magnetic field.

Electronic states exhibit topological quantum oscillations due to tunable Berry flux.

Abstract

Skyrmions are spatially localized magnetic swirls which carry a nonzero integer topological charge. We study crystals of skyrmions in a two-dimensional ferromagnet model with chiral interactions induced by the presence of broken inversion symmetry. We show that non-linear quartic mode-coupling terms allowed by symmetry enhances the Zeeman-field range over which the skyrmion-crystal phase remains stable. Furthermore, it leads to a significant dependence of the lattice constant of this spin crystal over this wide field range. Conduction electrons coupled to such a tunable spin crystal are shown to experience a Berry-flux density which varies with the Zeeman field. Such tunable skyrmion crystals provide a distinct realization of a Berry-Hofstadter butterfly, resulting in a phenomenon we term "topological quantum oscillations" in the electronic density of states and associated observables.