Observation of a Thermodynamic Distinction Between Brillouin Zone Center and Boundary Exciton States in MnF2

Abstract
The shape of the intrinsic-emission magnon sideband is well described assuming a wave-vector representation but with zero dispersion for the exciton. An observed difference in the decay rates of the intrinsic-emission zero-magon line and magnon side-band implies that the zone-center and zone-boundary excitons are distinct thermodynamic states. Thus, the exciton wave-vector states are, at least approximately, eigenstates.