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 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 neutron spectroscopy 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.
