|Dielectric and IR spectroscopy||THz science and technology||Light and neutron scattering||
|Solid-state materials science||
Main activities of Department of Dielectrics cover experimental and theoretical investigations of high-permittivity insulators like liquid crystals, ferroelectrics, multiferroics, piezoelectrics, semiconductor nanostructures, and low-loss materials.
- Dielectric and IR spectroscopy
- THz science and technology
- Light and neutron scattering
- Theory and simulations
- Solid-state materials science
- Liquid crystals
The most significant fresh scientific results of our deparment are listed in the section Highlights.
Department of Dielectrics, Institute of Physics of the Czech Academy of Sciences
Semimetrics Ltd., Kings Langley, England
Bohuslav Březina obituary
Ing. Bohuslav Březina, CSc. passed away on February 4, 2019.
After obtaining his PhD in 1955 he joined the Ceramic Research Institute in Klenčí and Hradec Králové. In 1957 he joined the Institute of Physics of the Czechoslovak Academy of Sciences where he focused on growing single-crystals exhibiting ferroelectric properties. He conducted a truly pioneering research in a dramatically developing field.
Spatio-temporal distribution of relative Ti-O6 displacements in cubic BaTiO3
BaTiO3 is often considered a model ferroelectric material in which the dielectric properties are defined by the displacements of Ti ions with respect to surrounding oxygen atoms. However, despite the decades of a dedicated research, certain controversies have remained as to the description of collective movements of the Ti ions. We approached this problem using nonoscale-oriented X-ray scattering methods and large-scale atomistic simulations . Together these allowed us to show that the Ti dynamics can be exhaustively explained by phonons excited on a timescale of picoseconds.
Electric-field-induced transition from incommensurately to commensurately modulated phase
Antiferroelectric-like polarization hysteresis loops in Ba4Sm2Ti4Nb6O30 and Ba4Eu2Ti4Nb6O30 were explained by electric-field induced structural phase transition from nonpolar incommensurately modulated structure to polar and commensurately modulated phase . This discovery opens new perspective direction of investigation of lead-free materials for possible electric energy storage.
Quantum theory of terahertz conductivity of semiconductor nanostructures
In collaboration with T. Ostatnický of Charles University we participated to the development of the first theory of the quantum conductivity describing the transport in the terahertz spectral range, which does not contain internal contradictions. We have shown that the broken translation symmetry of the nanostructures induces a broadband drift-diffusion current which must be explicitly taken into account.
Přibramite, a new Se-containing mineral from the Czech Republic, characterized by Raman spectroscopy
Minerals containing selenium are interesting and worthy to study due to its inherent photovoltaic effect. The characterization and understanding of these natural minerals is important to be able to make synthetic analogues.
Unusual behaviour under the applied electric field for new cholesteric liquid crystals with extremely short pitch
Unusual behaviour of new cholesteric liquid crystals has been observed under applied electric field. Positive dielectric anisotropy causes reorientation of the long molecular axis along the applied electric field direction. Due to extremely short pitch length a stripe texture has been observed under applied electric field. A model based on disclinations has been proposed and anchoring energy evaluated.
The ferroelectric phase transition of the tetragonal tungsten-bronze SBN-35 unveiled
The structural ferroelectric-paraelectric transition has been definitely observed by electron diffraction tomography in the tetragonal tungsten-bronze (TTB) Sr0.35Ba0.61Nb2O6.04 (SBN-35) from the paraelectric group P4/mbm to the ferroelectric Pmbm. At 625 K, the refined structure shows that the average structure of SBN-35 is tetragonal with an almost negligible orthorhombic distortion [Fig.1].
Departure from BCS response in photo-excited superconducting NbN films observed by terahertz spectroscopy
Ultrashort laser pulses can be used to induce transient exotic states of matter and cause phenomena of a vital interest such as room temperature superconductivity. We have focused on the photo-induced dynamics in niobium nitride (NbN) thin films  under strong excitation.