Meron, skyrmion, and vortex crystals in centrosymmetric tetragonal magnets

TL;DR

This paper proposes a mechanism for stabilizing meron, skyrmion, and vortex crystal spin textures in centrosymmetric tetragonal magnets, revealing their potential to induce topological electronic states like Chern insulators and Weyl semimetals.

Contribution

It introduces a simple, field-free stabilization mechanism for various topological spin textures in centrosymmetric tetragonal magnets, expanding understanding of their formation and electronic effects.

Findings

Meron and skyrmion crystals can form without magnetic field.

Topological textures induce Chern insulators and Weyl semimetals.

Rich variety of spin textures persists under magnetic field.

Abstract

The recent experimental confirmation of a transformation between meron and skyrmion topological spin textures in the chiral magnet Co$_8$Zn$_9$Mn$_3$ [S.-Z. Lin et al., Phys. Rev. B 91, 224407 (2015); X. Z. Yu et al., Nature 564, 95 (2018)] confirms that the skyrmion crystals discovered in 2009 [S. M\"{u}hlbauer et al., Science 323, 915 (2009)] are just the tip of the iceberg. Crystals of topological textures, including skyrmions, merons, vortices, and monopoles, can be stabilized by combining simple physical ingredients, such as lattice symmetry, frustration, and spin anisotropy. The current challenge is to find the combinations of these ingredients that produce specific topological spin textures. Here we report a simple mechanism for the stabilization of meron, skyrmion, and vortex crystals in centrosymmetric tetragonal magnets. In particular, the meron/skyrmion crystals can form even in absence of magnetic field. The application of magnetic field leads to a rich variety of topological spin textures that survive in the long wavelength limit of the theory. When conduction electrons are coupled to the spins, these topological spin textures twist the electronic wave functions to induce Chern insulators and Weyl semimetals for specific band filling fractions.