title: Multiple soft-mode vibrations of lead zirconate.
abstract: Polarized Raman, IR, and time-domain THz spectroscopy of orthorhombic lead zirconate single crystals have yielded a comprehensive picture of temperature-dependent quasiharmonic frequencies of its low-frequency phonon modes. It is argued that these modes primarily involve vibrations of Pb ions and librations of oxygen octahedra. Their relation to phonon modes of the parent cubic phase is proposed. Counts of the observed IR and Raman active modes belonging to distinct irreducible representations agree quite well with group-theory predictions. Analysis of the results yields insight into the phase transition mechanism, involving a soft ferroelectric branch coupled by a trilinear term to another two oxygen octahedra tilt modes.
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Hlinka
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: T
authors.initials: T
authors.lastname: Ostapchuk
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: E
authors.initials: E
authors.lastname: Buixaderas
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: C
authors.initials: C
authors.lastname: Kadlec
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: P
authors.initials: P
authors.lastname: Kuzel
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: I
authors.initials: I
authors.lastname: Gregora
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Kroupa
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: M
authors.initials: M
authors.lastname: Savinov
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: A
authors.initials: A
authors.lastname: Klic
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Drahokoupil
authors.affiliation: Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea, P.K. 644, 48080 Bilbao, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Etxebarria
authors.affiliation: Institute of Materials Science, University of Silesia, Bankowa 12, PL-40-007 Katowice, Poland.
authors.forename: J
authors.initials: J
authors.lastname: Dec