Laboratoire de Physique Théorique
Toulouse - UMR 5152

Quantum spin systems exhibit an enormous range of collective excitations, but their spin waves, gapped triplons, fractional spinons, or yet other modes are generally held to be mutually exclusive. In this presentation, I will show by neutron spectroscopy on SeCuO3 that magnons, triplons, and spinons are present simultaneously. I will demonstrate that this is a consequence of a structure consisting of two coupled subsystems and identify all the interactions of a minimal magnetic model. These results serve qualitatively to open the field of multi-excitation spin systems and quantitatively to constrain the complete theoretical description of one member of this class of materials.