title: Local symmetry breaking by impurities and mode splitting in doped SmS.
abstract: We introduce the idea of local symmetry breaking by impurities to explain the recently observed splitting of the J=0-->1 propagating excitation in doped Sm1-xYxS. While preserving the global cubic symmetry of the crystal, Y impurities change the local crystal-field environment of each Sm ion from cubic to tetragonal, thereby splitting the J=1 triplet into a m(i).J=0 level with energy Delta(1) and a m(i).J=+/-1 doublet with energy Delta(2)>Delta(1). A model with a randomly oriented quantization axis m(i) fits not only the observed mode frequencies but also their intensities, which strongly depends on the wave vector.
authors.affiliation: Solid State Division, Oak Ridge National Laboratory, Tennessee 37831-6032, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Fishman
authors.forename: S H
authors.initials: SH
authors.lastname: Liu