title: Coexistence of the phonon and relaxation soft modes in the terahertz dielectric response of tetragonal BaTiO3.
abstract: The dielectric response to infrared waves polarized along the tetragonal axis of a ferroelectric single-domain crystal of BaTiO3 was determined by time-domain THz spectroscopy and Fourier-transform infrared reflectivity techniques. In addition to the three well-known polar lattice modes, the experiment shows an additional mode of the relaxation type in the THz spectral region, which accounts for the Curie-Weiss behavior of the c-axis dielectric constant. A comparison of experimental results with ab initio based effective-Hamiltonian simulations allows us to elucidate its relation to the order-disorder model of Comes, Lambert, and Guinier [Solid State Commun. 6, 715 (1968)10.1016/0038-1098(68)90571-1].
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, Prague 8, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Hlinka
authors.forename: T
authors.initials: T
authors.lastname: Ostapchuk
authors.forename: D
authors.initials: D
authors.lastname: Nuzhnyy
authors.forename: J
authors.initials: J
authors.lastname: Petzelt
authors.forename: P
authors.initials: P
authors.lastname: Kuzel
authors.forename: C
authors.initials: C
authors.lastname: Kadlec
authors.forename: P
authors.initials: P
authors.lastname: Vanek
authors.forename: I
authors.initials: I
authors.lastname: Ponomareva
authors.forename: L
authors.initials: L
authors.lastname: Bellaiche