title: Second sound in SrTiO3.
abstract: We study collective phonon excitations in SrTiO3 by low-frequency light scattering. We employ extended thermodynamics for phonon gas to construct a theoretical spectral function that is applicable regardless of local thermal equilibrium. Our analysis reveals the temperature dependence of tauN, the relaxation time for the momentum-conserving phonon collisions (normal processes), in SrTiO3. These results indicate that the previously reported anomalous soundlike spectrum originates from second sound, which is a wavelike propagation of heat.
authors.affiliation: Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
authors.forename: Akitoshi
authors.initials: A
authors.lastname: Koreeda
authors.forename: Ryuta
authors.initials: R
authors.lastname: Takano
authors.forename: Seishiro
authors.initials: S
authors.lastname: Saikan