The multicomponent lineshape of the anharmonic A₁(TO) phonon in PbTiO₃

Abstract

Detailed Raman studies of the optical phonons in single-crystal PbTiO₃ indicate that the frequencies and symmetry assignments in the literature must be revised. In this study, all optical phonon modes are directly observed and are shown to rigorously obey Raman selection rules. The angular dependence of the phonon frequencies indicates that the energy of the lowest frequency A₁(TO) mode, which exhibits an anomalous anharmonisity-induced lineshape, is higher than the energy of the lowest frequency E(LO) mode at 300°K.