

Past international projects (last six years):
The realization of efficient, cheap, reliable, scalable and portable terahertz (THz) radiation sources and detectors is one of the important objectives in modern applied physics. THz emitters and detectors have potential applications in biology, medicine, security and nondestructive in-depth imaging. However none of the existing THz devices satisfy the application requirements. The project consortium, which includes teams from the leading European universities: Durham, Vilnius, Paris-7, Exeter, St. Petersburg, Prague, Amiens, University of Iceland, Swiss Company ""Alpes laser"" and several industrial associated partners, proposes a broad range of new approaches aiming to bridge the ""terahertz gap"":
- Polariton-based THz emission using microcavities in the strong coupling regime,
- New types and concepts of semiconducting materials for short pulsed THz emission,
- Carbon nanotubes and graphene as THz emitters and detectors,
- Application of Ferroelectric and Multiferroic materials for THz devices.
To achieve this objective, we are planning to educate and train a team of collaborating young physicists and device engineers able to conduct research and exploit its application in this new area
(hide abstract)Past Czech projects (last six years):
Within the project, new types of self-organized systems based on liquid crystals will be prepared and studied. Physical aspects of self-organization and stabilization of complex topological soft matter superstructures will be explored with respect to various conditions in the confined geometries.
(hide abstract)Understanding of the photoconductivity mechanisms in semiconductors on the nanoscopic level is a crucial prerequisite for the conception of novel optoelectronic and photovoltaic applications. Terahertz conductivity spectra provide information on the charge transport phenomena, which occur typically at this length scale, without the need of electrical contacts to be attached. In this project we will develop a concerted experimental and theoretical approach for microscopic description and proper understanding of ultrafast photoconductivity in nanoscale semiconductor systems. In optical pump – terahertz probe experiments we will emphasize an ultra-broadband spectroscopic aspect. In theory we will focus on the quantum description of the mechanisms of charge carrier localization in semiconductor nanostructures and on phenomena connected with the onset of the nonlinear transport regime including an appropriate effective medium theory description of the morphology of samples.
(hide abstract)Cobalt oxides comprise a wide group of materials in which important electron correlations lead to a large richness of interesting properties (e.g. large thermoelectric coefficient or superconductivity). The cobalt ions can frequently attain different electronic configurations, which is at the root of complex and often contradicting behaviors with varying temperature and material composition. Charge transport is one of the most important processes which reflect the internal state of these materials, and it is also of fundamental interest in potential applications. In cobaltites, we will study namely the mechanism of the metal-insulator transition. In layered cobaltates, we fill focus on the relation between charge transport and magnetic ordering. We will systematically study the conductivity in the terahertz spectral range, which permits a clear identification of charge transport mechanisms and charge confinement both in single crystals and in polycrystalline systems. Combination with common characterization methods will allow gaining a global picture of the behavior of the oxides.
(hide abstract)Biological macromolecules and structures display significant electric polar states. Regions of electric dipoles and/or multipoles with different vector moments depend on conformation of the polypeptide chain and amino acid residues. The essential polar structures in eucaryotic cells are formed by microtubules, hollow tubes of 25 nm outer diameter forming a radial system from the centrosome to the cell membrane. Microtubules display spectrum of conformational states, resonant spectra below 20 GHz, and spectra at 20 THz (700 cm-1), in optical and UV regions, and digital memory (500 bits). Microtubules in cells and separated microtubules will be investigated. Measurement by contemporary methods of Raman spectroscopy (SERS, TERS) would disclose temperature dependence of ferroelectric states up to 40 ºC. Evaluation of the effects of external electric potential and PFM mapping would serve a basis for assessment of the conformation changes.
(hide abstract)The project focuses on investigation of the structure and properties of ideal two-dimensional nanoscale objects: domain walls and similar interfaces in modern ferroelectric materials. The research will be targeted to explore the nature and application potential of three recently reported discoveries:
- Ferroelectric photovoltaic effect on domain walls of bismuth ferrite,
- Exotic chiral domain wall species in rhombohedral barium titanate and
- Giant softening of elastic constants of relaxor ferroelectrics.
The project aims at studying the origin of magnetoelectric coupling in various multiferroic materials, i.e. materials exhibiting simultaneously ferroelectric and magnetic orders. THz, Raman and infrared spectroscopy measurements of electromagnons and phonons will allow us to study the dynamic magnetoelectric coupling and the dynamics of ferroelectric phase transitions (soft modes). Dielectric spectroscopy from 10 mHz to 20 GHz will be used for studying the spin-phonon and static magnetoel. couplings. We will study TiO2 thin films and superlattices of EuO and BaO; these materials are paraelectric in bulk samples, but in films, the ferroelectric state will be induced by mechanical strain owing to an epitaxial growth on substrates. In EuTiO3 thin films, a vertical strain induced by MgO nanopillars will be used to change the order from antiferromagnetic to ferromagnetic and to induce the ferroelectric state above 300 K. Inelastic neutron scattering will be used for measuring magnon branches in hexaferrites and for confirmation of predicted short-range magnetic order in EuTiO3 near 300 K.
(hide abstract)Theoretically predicted strong magnetoelectric coupling will be studied in multiferroic Sr1-xBaxMnO3 a Ni3TeO6. We will also investigate following new potentially multiferroic materials: Pb2MnTeO6, Ni3-xCoxTeO6 a Ni3-xMnxTeO6. We will focuse our interest mostly on dynamical magnetoelectric coupling and search for electromagnons in THz and Raman spectra.
(hide abstract)In the project new approaches will be developed for fabrication of new self-organized materials based on liquid crystals (LCs) and various nanoparticles providing targeted optical, dielectric, magnetic or multiferroic properties for future technologies. The fluidity of LCs enables them to be strongly responsive to external stimuli, such as electric or magnetic fields, illumination by a definite wave length, mechanical stress, surface effects etc. Grafting the inorganic nanoparticles (magnetic, metallic or ferroelectric) with organic mesogenic molecules(functionalization) facilitates bottom-up self-organization of nanoparticles due to self-assembling nature inherent to the LC compounds. Additionally, this grafting can also implement desirable physical properties to the resulting system. We anticipate that combining the unique nanoparticle properties with that provided by liquid crystals might lead to a new functionality not obtained for the single components.
(hide abstract)In the project new approaches will be developed for fabrication of new self-organized materials based on liquid crystals (LCs) and various nanoparticles providing targeted optical, dielectric, magnetic or multiferroic properties for future technologies. The fluidity of LCs enables them to be strongly responsive to external stimuli, such as electric or magnetic fields, illumination by a definite wave length, mechanical stress, surface effects etc. Grafting the inorganic nanoparticles (magnetic, metallic or ferroelectric) with organic mesogenic molecules(functionalization) facilitates bottom-up self-organization of nanoparticles due to self-assembling nature inherent to the LC compounds. Additionally, this grafting can also implement desirable physical properties to the resulting system. We anticipate that combining the unique nanoparticle properties with that provided by liquid crystals might lead to a new functionality not obtained for the single components.
(hide abstract)The biocompatibility of materials for hard tissue implants is under intensive investigation nowadays. We propose to provide improved biocompatibility by using the influence of an electric charge on the living system. As substrates for thin ferroelectric layers, we will prepare promising Ti alloys (without suspect components, and preferably as thin coatings). Substrates with excellent corrosion resistance will be characterized by mechanical, chemical and tribological tests. The surface of these Ti alloys will be covered by a spontaneously polarized ferroelectric film (BaTiO3, K(Ta,Nb)O3, etc. in single phase or composite form), with an electric charge on the surface. Mechanical, tribological and dielectric properties important for bioapplications will be tested. The project is based on determining the impact of the overlayer properties on the adhesion, growth, differentiation and viability of osteogenic cells in vitro. We will estimate the possible immune activation of cells growing on the material and the potential genotoxicity of the material.
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