Formation of a Topological Monopole Lattice and its Dynamics in Three-dimensional Chiral Magnets

TL;DR

This paper provides numerical evidence for a three-dimensional monopole lattice in chiral magnets and explores its dynamic properties, advancing understanding of topological magnetic textures beyond Skyrmions.

Contribution

It introduces a microscopic model supporting a monopole crystal phase and analyzes its collective excitations through Monte Carlo and real-time simulations.

Findings

Monopole-anti-monopole crystal forms a rock-salt structure.

The monopole crystal exhibits a single collective mode in GHz range.

Supports the existence of 3D monopole lattices in chiral magnets.

Abstract

Topologically protected swirl of the magnetic texture known as the Skyrmion has become ubiqui- tous in both metallic and insulating chiral magnets. Meanwhile the existence of its three-dimensional analogue, known as the magnetic monopole, has been suggested by various indirect experimental sig- natures in MnGe compound. Theoretically, Ginzburg-Landau arguments in favor of the formation of a three-dimensional crystal of monopoles and anti-monopoles have been put forward, however no microscopic model Hamiltonian was shown to support such a phase. Here we present strong numerical evidence from Monte Carlo simulations for the formation of a rock-salt crystal structure of monopoles and anti-monopoles in short-period chiral magnets. Real-time simulation of the spin dynamics suggests there is only one collective mode in the monopole crystal state in the frequency range of several GHz for the material parameters of MnGe.