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Areas of research
Nature of collective interactions in new potentially useful materials including:
- Superconductivity mechanisms in copper- and iron-based compounds and organic superconductors.
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Phase transition mechanisms and the nature of collective excitations and ground states in systems with competing order parameters (manganites, multiferroics, etc.).
Relevance of the proposed research is due to the fact that the characteristic excitations energies of the ground state (energy gaps and pseudo-gaps, collective modes, carrier relaxation frequencies) of those objects are on the order of milli-electronvolt, that corresponds to the energy of a quantum of THz radiation. At the same time, conducting, and especially superconducting materials are particularly difficult objects for THz investigation. Therefore, there is very little relevant and reliable experimental data available in the literature. As a consequence, progress in understanding the fundamental processes which underlie the phenomena being studied is held up.
Specific tasks and aims, approximate timeframes and expected results. Getting new information on the microscopic mechanisms of conductivity and superconductivity in new high-temperature super-conductors based on iron and in cuprates; the investigation of phase transition mechanisms and the nature of collective exci tationsin overdoped manganites RE1-xMxMnO3(x>0.5, RE — rare earth, M — alkali metal), in the Co, Ni, Fe groups Cr2O4, Sr3Co2Fe24O41 and in the family of organic conductors and super-conductors based on BEDT salts; the investigation of the origin of the ground state of topological insulators of different types. It is proposed to obtain high quality samples of a number of unique compounds and their properties (using the methods x-ray structure analysis, low angle neutron scattering, low angle x-ray scattering, statistical measurements etc) and to conduct the first measurements of THz-IR conductivity and dielectric permittivity spectra over a wide range of temperatures ( 5 К – 300 К) and, if necessary, magnetic fields (0 – 5 Tesla).
The investigation of the physical properties of objects at the nano and sub-nano scales:
1. The dynamics of single water molecules in a nano-sized cages within crystal lattice of a dielectric.
2. The dynamics of molecular clusters isolated within nanoscale pores.
3. The terahertz electrodynamic of nano-heterostructures with quantum dots.
Relevance of the proposed research. In conditions when the object consists of a number of molecules which are significantly smaller than10^23 см-3, its properties can be cardinally different compared to those in its bulk state. Knowledge of the specifics of such properties is extremely important for understanding the dynamics of the molecule at a two-dimensional interface, in nanocavities, nanotubes or organized in planes/chains. A special role is assigned to water molecules and clusters. The area of interest concerns physics, chemistry, biology, geology and astrophysics. There is practically no reliable experimental material available in the literature.
Specific tasks and aims, approximate timeframes and expected results. The tasks of this project are to investigate: а) the nature of low-energy excitations of single water molecules, located in a sub-nanoscale cavity in a crystal lattice of beryll Be3Al2Si6O18; b) the collective behaviour of water H2O clusters, located in zeolites, fullerenes and carbon nanotubes; c) conductivity mechanisms for Ge/Si heterostructures with ordered masses of Ge quantum dots.
Optical and contact studies of proteins, self-assembling peptides and biological complex systems
1. The dynamics of water molecules in proteins.
2. The dynamics of protein secondary structure.
3. The mechanisms of long-range electron and ion transfer in natural biological and artificial self assembling peptide systems.
4. Spectral fingerprinting of tissues and microorganisms.
Relevance of the proposed research. Recent discovery of long-range electron transfer in so-called bacterial nanowires spurred interest to fundamental problem of charge conductivity within proteins. Modern solid state physics has developed great arsenal of methods and techniques for characterization of charges' origin and mobility within condensed phase which are not well known within biochemical society. We collaborate with microbiologists and biochemists to find out the origin of electrical conductivity observed in various proteins and conductive extracellular structures of electrogenic bacteria. We collaborate with chemists to synthesize artificial self-assembling peptides with enhanced electron conductivity.
Since the THz-range is extremely sensitive to state of water molecules within condensed phases we utilize our technique for detection of water molecules fractions depending on their bounding within proteins and other materials. This information may be very important for understanding of that how water acts in ferment catalysis and structural organization of proteins.
The normal modes of various secondary structures within proteins lie in terahertz frequencies. It makes possible to use the obtained data for identification of specific vibrations in proteins responsible for particular activity and allosteric regulation.
THz characterization and diagnostics of industrial materials and structures
1. Dielectric substrates for high-temperature superconducting films.
2. Elementary semiconductors, semiconductor connections.
3. Dielectrics with high values of dielectric permittivity.
4. Multi-layer dielectric and semiconductor structures and coatings.
Relevance of the proposed research. In the conditions when the working frequencies in modern micro- and optoelectronics are increasing and approaching terahertz band, it is particularly important to establish the dielectric parameters (absorption, dielectric permittivity) of the materials being used. Today the BWO spectroscopy remains the only method which provides the possibility of quantitatively characterizing the dielectric parameters of very different industrial materials. The accuracy of the defined characteristics is significantly higher than can be guaranteed using TDS spectroscopy, particularly at sub-terahertz frequencies (less than 200–300 GHz).
Specific tasks and aims, approximate timeframes and expected results. The aim of this project is to obtain reliable quantitative data on the dielectric properties (dielectric permittivity, loss tangent) of the compounds and the possibilities for their use in modern micro- and optoelectronics. In the temperature range of interest the THz – sub THz dielectric parameters of those compounds with the potential for corresponding use - MgO, SrLaAlO4, DyScO3, SrTiO3 and others will be measured.
Equipment and methods for the terahertz frequency range
1. The design and optimization of methods for the quantitative dielectric measurements of the THz parameters of liquid materials.
2. The design of software intended for the analysis and processing of THz spectra materials and layered systems.
3. The design and improvement of equipment and units for THz spectrometers.
4. The design of onboard heterodyne spectrometers in the terahertz range for use in space vehicles.
5. The use of heterodyne and waveguide techniques in the infrared and optical range of spectra.
Relevance of the proposed research. Accumulated advanced experience in THz spectroscopy enables the staff proposed to set up a laboratory that makes it possible to conduct work that furthers the enhancement of unique equipment and methods. The aim of this is to extend the range of objects, structures, fields of application of external influences (temperature, magnetic fields, pressure), increasing the speed and automation of the processes of measurement and data analysis.
Specific tasks and aims, approximate timeframes and expected results. The task of this project is to develop new methods for the quantitative measurements, including low temperature, of THz dielectric parameters of liquid materials from different sources, including biological. This work will include the development of cuvette units and software for the processing of experimental spectra of those relevant multilayer systems which contain the objects being researched as components. Moreover, it is possible that the need for establishing principally new measurement schemes and configurations will arise.
The use of THz radiation and its properties in the education process
1. Practical laboratory experiments based on THzand sub-THz radiation.
2. The design of new experiments for THz laboratory course.
3. The development of a set of demonstration programs.
Relevance of the proposed research. Experience gained while working with THz and sub-THz waves has made possible the development of a complex of laboratory experiments, the use of which will allow students to acquire knowledge of the basics of electrodynamics and of the electrodynamic properties of materials and structures. The main advantage of such course is that the used radiation wavelength is 2mm, which reduces the need for reference materials when compared to analogical experiments with visible radiation. It is proposed to develop new experiments.
Specific tasks and aims, approximate timeframes and expected results. The tasks of this project include the optimization of the educationsl process based on the use of a set of quasi-optical experiments and on the development of new experimental exercises. Moreover, there is interest in the development of a software package for the study of interference effects and multilayer structures found as structural elements within materials of different types – dielectrics, conductors, superconductors, subatsnces with resonant absorption and magnetic line absorption.
Remote probing and astrophysical research in the terahertz range
1. Rotational and oscillating-rotational molecular spectra
2. Submillimeter astrophysics
3. Direct and reverse tasks for distance probing in the terahertz range
4. The exospheres of cosmic bodies without atmosphere – the key to their internal construction.
