PHONON ANOMALIES IN SRTIO3 IN THE QUANTUM PARAELECTRIC REGIME

New inelastic neutron-scattering and Brillouin-scattering results are reported for pressure-oriented SrTiO3 crystals at temperatures below the structural transition. The measurements reveal an unexpectedly large number of anomalies at small frequencies and wave vectors in the quantum paraelectric region. The anomalies include a strong depression of a TA-branch at unusually small wave vectors, an apparent splitting of the same branch, the lifting of a selection rule for the structural mode, and an anomalous temperature dependence of the elastic constant C-44.