title: High tunability of the soft mode in strained SrTiO(3)/DyScO(3) multilayers.
abstract: SrTiO(3)/DyScO(3) epitaxial multilayers with variable number and thickness (10-100 nm) of bilayers deposited on DyScO(3) substrates were investigated by means of time-domain terahertz spectroscopy at room temperature. A tensile strain develops in the SrTiO(3) films and shifts the eigenfrequency of the ferroelectric soft mode down by ∼25-45 cm(-1) with respect to the value found for single crystals. In all films the soft mode strongly hardens upon the electrical bias and a linear coupling to a silent excitation of relaxation type at 10 cm(-1) is observed. We show that the change in the THz and sub-THz response of the layers with an increasing field is determined solely by the soft mode eigenfrequency and we propose a phenomenological model describing the origin of the tunability and the peculiar properties of the ferroelectric soft mode in the terahertz spectral range.
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.forename: F
authors.initials: F
authors.lastname: Kadlec
authors.forename: H
authors.initials: H
authors.lastname: Němec
authors.forename: P
authors.initials: P
authors.lastname: Kužel
authors.forename: J
authors.initials: J
authors.lastname: Schubert
authors.forename: G
authors.initials: G
authors.lastname: Panaitov