Hybrid Goldstone modes in multiferroic YMnO3 studied by polarized inelastic neutron scattering

We used polarized inelastic neutron-scattering measurements to shed light on the spin-lattice quantum entanglement in multiferroic materials. We report an evidence for hybrid elementary excitations made of a mixing between spin waves and phonons, which can be considered as multiferroic Goldstone modes. We argue that the Dzyaloshinskii-Moriya interaction could be at the origin of this hybridization.