Magnon spectrum of the helimagnetic insulator Cu2OSeO3

TL;DR

This study uses inelastic neutron scattering to map the three-dimensional magnon spectrum of Cu2OSeO3, revealing distinct magnon modes and verifying the microscopic magnetic interactions responsible for its complex magnetic phases.

Contribution

It provides the first comprehensive experimental magnon spectrum of Cu2OSeO3, confirming theoretical models of its magnetic interactions with high accuracy.

Findings

Identification of high- and low-energy magnon modes separated by an energy gap

Excellent agreement between experimental data and theoretical spin-dynamical calculations

Quantitative verification of magnetic interactions in Cu2OSeO3

Abstract

Complex low-temperature ordered states in chiral magnets are typically governed by a competition between multiple magnetic interactions. The chiral-lattice multiferroic Cu2OSeO3 became the first insulating helimagnetic material in which a long-range order of topologically stable spin vortices known as skyrmions was established. Here we employ state-of-the-art inelastic neutron scattering (INS) to comprehend the full three-dimensional spin excitation spectrum of Cu2OSeO3 over a broad range of energies. Distinct types of high- and low-energy dispersive magnon modes separated by an extensive energy gap are observed in excellent agreement with the previously suggested microscopic theory based on a model of entangled Cu4 tetrahedra. The comparison of our INS data with model spin-dynamical calculations based on these theoretical proposals enables an accurate quantitative verification of the fundamental magnetic interactions in Cu2OSeO3 that are essential for understanding its abundant low-temperature magnetically ordered phases.