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Laboratory of Terahertz Spectroscopy

Areas of research


Research into the nature of collective electron interactions in new potentially useful materials including:

 

1. Superconductivity mechanisms in copper-iron alloys and organic superconductors.

2. Phase transition mechanisms and the nature of collective activation in systems consisting of several competing order parameters (manganites, multiferroics)

3. Collective activation in organic small-scale conductors and superconductors.

 

Relevance of the proposed research is due to the fact that the characteristic activation energies of the basic state(energy gaps and pseudo-gaps, collective modes, carrier relaxation frequencies) of those objects presented (for investigation) are on the order of milli-electron volts, that is they correspond to the energy of a quantum of THz radiation. At the same time, conducting, and especially superconducting, materials are particularly complex objects for THz investigation. Therefore, there is practically no 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. The acquisition of new information on the microscopic mechanisms of conduction and super-conduction in new high-temperature super-conductors based on iron and in cuprates;the investigation of phase transition mechanisms and the nature of collective activation in 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 natures of the basic state of topological insulators of different types. It is proposed to obtain high quality samples of a number of unique bonds 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 di-electric permittivity spectra over a wide range of temperatures (5К – 300К) and, if necessary, magnetic fields (0 – 5 Tesla).

 

The investigation of the physical properties of objects at the nano and sub-nano scale

 

1. The dynamics of single molecules of water in a nanoscale cavity in a crystal.

2. The dynamics of molecular clusters isolated in nanoscale pores.

3. The terahertz electrodynamic of nano-heterostructures with quantum dots.

 

Relevance of the proposed research. In conditions when the object being investigated consists of a number of molecules which are significantly smaller than1023 см-3­, its properties can be cardinally different than its properties when in its mass (bulk) state. Knowledge of the specifics of such properties is extremely important for understanding the conduct 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 inthecurrent literature.

 

Specific tasks and aims, approximate timeframes and expected results. The tasks of this project are to investigate: а) the nature of low-energy activations of single water molecules, located in a sub-nanoscale cavity in a crystal lattice of beryllium Be3Al2Si6O18; b) the collective behaviour of water H2O clusters, located in volume and extended cavities in zeolite, fullerene and carbon nanotubes; c) conductivity mechanisms for Ge/Si heterostructures with ordered masses of Ge quantum dots.

 

 

Terahertz spectroscopy of biological molecules, systems and materials 

 

1. The dynamics of chains of water molecules in biological ion transport systems.

2. The dynamics of separate domains in fermentation systems.

3. The discovery of the mechanisms of long-rangeelectron and ion transfer in natural biological and artificial biocompatible systems.

 

Relevance of the proposed research. Water is an important component of protein and nucleoprotein complexes in biological systems. It bears both a structural and functional load and plays a direct part in catalytic processes.Due to the success of the last twenty years in the field of protein crystallization, in particular in transmembrane transport systems, the colossal role that water plays in the mechanisms for the transport of hydrogen ions and other cations has become clear. In fact, thanks to the data from x-ray structural analysis it has become possible to observe the formation of chains from molecules of water connected to proteins bonded by hydrogen links “stitched together” throughout the membrane. The number of water molecules in such a chain can reach 12–15. There is a large probability that such a cluster can form a single oscillating system with a characteristic resonance in the terahertz range. The discovery of the corresponding resonances leads to a new, deeper understanding of the energy of a multitude of important biological processes connected with the storage of the chemical potential on the membrane and the distribution of ions in the membrane system. In its turn, this information is important for the creation of highly-effective artificial membrane systems for the transformation of energy, including those for membrane fuel elements. 

 

Of no less interest is theelucidation of the recently discovered mechanisms of long-range electron conductivity in bacterial syncytia (symplasm). The nature of the transfer of electrons in such systems and also the mechanism for the distribution of energy obtained between the cells participating in the syncytia remains undiscovered. The Terahertz spectroscopy method is able to provide key information about the character of the conductor and its analogues in the non-animate field. Finally, spectroscopy at the terahertz range can serve as afine, non-destructive instrument for the analysis of water content in the damaged materials of organisms, cell cultures and food products. Such information is important, for example, to determine the character of damaged skin coverings and for determining forms of skin cancer, as the different types of tumor can be fully characterized by the amount of water in their structure.

 

Specific tasks and aims, approximate timeframes and expected results. In the next 2-3 years the main oscillation modes of the enzymes of the mitochondrial respiratory chain, the most commonly found ion transporters in nature, will be studied. The dependence of the effectiveness of the work of the mitochondrial proton pumps built into artificial membranes on the amount of water in the system and the intensity of the corresponding oscillation mode will be assessed. Also, using the methods of terahertz microscopy, atomic force microscopy, spectroscopy of single molecules research will be conducted into the nature of electron transference in syncytia of the bacteria Desulfobulbus. Based on the main results obtained in these studiesapplications using the natural mechanism of highly effective electrogene transmembrane ion transfer with the aim of membrane energetics will be proposed. The discovery of the mechanism of far-reaching electronic transfer in the syncytia can serve as the basis for the creation of new types ofbiocompatible electron-conducting materials.

 

The characterization and diagnostics of industrial materials and structures 

 

1. Dielectric coatings 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 speed of components and junctions in modern micro- and optoelectronics are increasing and approaching terahertz frequencies, it is particularly important to establish the dielectric parameters (absorption, di-electric permittivity) of the materials being used. As of todayBWT spectroscopy remains the only method which provides the possibility of quantitativelycharacterizing the dielectric parameters of very different industrial materials. The accuracy of the defined characteristics is significantly higher than can be guaranteed using TDS spectrometry, 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 bonding and the possibilities for its 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, SrTiO3and others will be measured.

 

Equipment and methods for the terahertz range of frequencies 

 

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 enhancement 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 spectrometryenables 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 work based on THzand sub-THz radiation.

2. The design of new experiments for THz laboratory practice.

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 practice is that the length of the waves of the radiation used 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 study process based on the use of a selection 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 media of different types – dielectrics, conductors, superconductors, media 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.


Supervisor: Boris Gorshunov



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