RpLab | MSPU | In Russian
Scientific school at the GEP Department of Moscow State Pedagogical Institute (University now) started to be formed in 30th of XX century. That time, a number of famous physicists were working at the Department, including I. E. Tamm (Nobel Prize winner), G. S. Landsberg, and A. A. Andronov. Under their supervision, the studies at the field of radiophysics were initiated; this field was under active development in country that time, and the progress was quite visible.
For many years, the development of scientific school at GEPD was attributed to the name of Prof. Nikolai. N. Malov and his outstanding disciple, a Correspondent Member of Russian Academy of Education, a long-term GEPD Chairman, Professor Evgeny M. Gershenson. At present time, the department and its scientific efforts are leaded by its current Chairman, Professor Gregory N. Goltsman. Since its early days and up to now, the departmental scientific school is still gravitating to radiophysics studies in spite of appearance of numerous new directions of research carried on in the Lab.
The scientific school at the GEP Dept. was always engaged to the most actual problems of radiophysics known in the world and country. The period before WWII and during the first after-war years were characterized by the initiation of the active research in RF and microwave. During these years, the first results were obtained at high frequencies under supervision of Prof. N. Malov. Later on, these results served as the base for modern microwave waveguide propagation theory [1].
At the very end of 50th, two young scientific talents (the Professors then), i.e. Evgeny M. Gershenson and Valentin S. Etkin entered the Lab. Due to their joint efforts, the new Radiophysical Problems Laboratory (RPLab) was organized and became a largest scientific division at the pedagogical institutes of USSR. The further development of science school was made entirely within the walls of RPLab.
Being characterized as inclined into radiophysics, the scientific shool constantly expanded the research themes in according to overall development of radiophysics, which was, in numerous cases, a consequence of the studies accomplished in RPLab. For instance, at the end of 50th and beginning of 60th, a very first Soviet semiconductor diode parametrical amplifier was invented here, awarded the USSR State Prize in 1983.
During 60th and 70th, the research subjects circle was expanded significantly. These years, the main attention has been paid to the studies of physical processes in ideal crystals. The most prominent feature of this research was a thorough study of weakly bonded states in nearly-ideal crystals and the devices based on such crystals. These studies were carried on by the radiophysical methods, and the innovation of this approach was mainly in extremely high frequencies used in spectroscopy measurements (the wavelengths of λ ~ 0,5 ÷ 3 mm range were generated by the backward-wave tubes; this technology awarded the USSR State Prize in 1980). The magnetoresistive effects (cyclotron and electron paramagnetic resonance, in particular), impurity spectra&conductivity, and exciton states were studied using these advanced methods. These spectroscopy methods were used also to discover the negatively charged shallow impurity levels and positively charged acceptor levels in semiconductors (Si and Ge), and in very first observation of a hydrogen-like electro-dipole intrinsic transitions of the free excitons in Ge. These studies allowed not only for a complete explanation of the entire set of early physical observations, but for development of new methods of measurement the parameters of Ge, Si and InSb, used later in ultra-high semiconductor purification technology.
The continuation of the studiy of parametrical devices smoothly converted into a very practical design and development of ultra-low-noise microwave receivers (radiometers) used for remote sensing of the Earth and World Ocean. This work was carried on together with Space Research Institute of Russian Academy of Sciences, where a subsequent division was organized by the members of RPLab scientific school. This work was resulted in manufacturing of the unique radiometry instruments for plane- and ship-based studies of the Earth surface, including land, snow layers, sea surface, etc. Among those instruments is a very first in the world cryogenic receiver complex working at the liquid helium temperatures, based on Josephson junctions. These ultra-wideband receivers had the sensitivity limited by the fundamental laws only, and used for remote sensing studies carried on the ship board in the World Ocean. The developed radiometry instruments were successfully used for monitoring of the Earth surface. Among the accomplished experimental works was the only known observation of the sea waves made in remote Pacific Ocean areas.
One of the main scientific directions of study at the modern days is the research at the field of nonequilibrium phenomena and space-nonuniform processes in superconducting nanostructures. These nanostructures usually represent the very narrow channels made with ultrathin superconductor films with a thickness of few atomic layers. The subjects of study are the processes of energy relaxation and hot quasiparticle diffusion in extremely narrow ultrathin structures, a single-photon interaction with such nanostructures and ultrafast dynamics of the photo-induced phase slip centers, the charge disbalance and its relaxation for electron-like and hole-like excitations, Andreev reflection at the N-S-N (N-Normal, S- superconducting) and S-N interfaces, the proximity effects, and the s- and d-wave symmetry of the order parameter. The logical approximation of these scientific studies to applications was the development of the revolutionary new devices with record-high specs, ultra-low noise and ultrawideband receivers of TeraHertz range requiring extremely low Local Oscillator power, single-photon detectors of infrared and visible range having simultaneously picoseconds-range speed, very high quantum efficiency and extremely low dark counts. These newest directions of research include also a practical implementation of such devices in THz radioastronomy, including study of star formation in molecular clouds and space dust formations), in radiophysical studies, including remote sensing of high atmospheric layers for the purpose of monitoring the heterogenic chemical reactions and concentration of catalytic impurities, possibly responsible for ozon layer condition and global warming; in optics, to develop a new class of ultrasensitive receivers and single-photon fiber-optics communication; in electronics, for the purpose of noninvasive diagnostics of VLSI circuits and ultrafast RSFQ logic.
Currently, practically all the projects related to heterodyne THz radiastronomy and remote sensing of upper atmospheric layers of THz range are based on implementation of superconducting hot-electron bolometers (HEB). These devices came to existence as the result of fundamental research carried on by scientific school at GEPD. The world-known projects with HEBs used can be presented by such examples as the ground-base THz telescope for 1.03, 1.26 and 1.46 THz at the Atakama plateau in Chile, developed together with Harvard-Smithsonian Center for Astrophysics, USA, the space-based telescope HERSHEL for 1.5÷1.9 THz range developed together with Chalmers University of Technology, Sweden, the airplane-based project SOFIA for 4.7 THz range, the balloon-based project TELIS for 1.8 THz range developed together with Insitituit fur Webtraumsensorik und Planetenerkundung, Germany, the international THz telescope TREND based at the South Pole, etc.
Recent years, with the latest advances of heterodyne technologies toward higher frequencies it was found that the state-of-the-art low-noise tunnel Superconductor-Insulator-Superconductor tunnel junction Niobium mixers lost its sensitivity above a very vicinity of 1 THz frequency, corresponding to superconducting gap energy of Nb, the most popular superconducting material. The Shottky diode-based receivers for THz range, also, not only lost its sensitivity, but require very high Local Oscillator power, which is hardly achievable with modern solid-state oscillators. In contrary, the HEB heterodyne mixers do not have such a fundamental limitations in the short wavelength side, and demonstrate high sensitivity at very low LO power levels.
This particular result obtained at the GEPD is a direct consequence of very fundamental studies of nonequilibrium relaxation phenomena in ultrathin superconducting films carried out in RPLab since 80th [2-4], first published in open literature in 1990 [5]. Later on, in 1993, the rivalry publication of Yale University group was appeared [6] on superconducting mixer, where a similar electron heating effects was used but with a diffusion cooling channel. This last publication initiated a number of studies in USA, Germany, Netherlands and other Western countries, but these devices never became practical, in contrary to photon-cooled mixers developed at GEPD MSPU. This fact also served for a world-wide recognition of the scientific school at GEPD MSPU, especially at the field of THz technology.
An another important result was a discovery of photo-induced phase slip centers effects in current-driving superconducting channels and the related development of single-photon infrared detectors having picoseconds-speed, high quantum efficiency, and low dark counts, as well as its practical implementation for the purpose of VLSI circuit noninvasive diagnostics using weak infrared radiation coming from switching transistors in silicon chips [7-9]. This is an example of truly innovative work, where the entire path from fundamental discovery to commercial sales was made within 3 years only, demonstrating a modern style of work established in GEPD. Such a fast innovation introduction into the practice was made possible solely due to accumulation of original fundamental knowledge and top technological skills made within a previous, very long time research. Essentially, the GEPD already used the same style of work at its early years of existence in Soviet ere, which was made possible due to financial resources coming from industrial contracts with government agencies, plants, and institutes.
The studies of semiconductor Si single crystals found its today's prolongation, as well. The study of extremely pure single crystals with impurities concentration level below the necessary for a direct dielectric-metal transition allowed for discovery of entire set of new effects, such as hopping conductivity within hydrogen-like state band, indirect three-step trapping of photoexcited carriers, delocalization of hydrogen-like states at the electrical field, and the new conductivity mechanism due to hydrogen-like impurity states concentrated along the linear dislocations. The last contribution into the total conductivity can be several orders of magnitude higher than the regular impurity-induced conductivity. These developments in semiconductor science clearly demonstrate the continuity of the researcher generations at the GEPD. For instance, the pioneering works of Profs. Yu. A. Gurvitch and A. P. Mel'nikov found its continuation in discovery of negatively charged impurity centers in semiconductors.
Since the very beginning of the grant support system in Russia, the GEPD participated in the numerous scientific competitions and received a very large number of grants. Historically, the very first research competition in Russia was carried on by the Scientific Council on Superconductivity, created by the Russian Government Commission leaded that time by its Prime Minister N. I. Ryzhkov. This grant was received in 1989-1991 and had the size about 2 M rubles per year or approximately $1M for three years in total. This investment allowed purchasing the state of the art technological equipment, which is still under intensive use in GEPD Lab. This grant can be compared to another unprecedented in size investment of Russian Government made to MSPU as one of the winners of Russian Innovative University Competition of 2006; it allowed acquiring another significant portion of the modern technological equipment.
The important factor stimulating the young researchers at GEPD is an easy access to all the necessary materials and top-class equipment. It should be emphasized that the most of experimental work in Lab requires very low temperatures, which require, in turn, a significant amount of liquid helium. For this purpose, the lab owns the helium liquefier station, which worked without stop even at the most tough times. This station supplies the Lab with about 4000 liters of liquid helium per year. All the time, the Lab is trying to acquire the equipment from any possible sources, including unexpected ones. For instance, in 2003, the IBM Watson Research Center provided the Lab with a gift - an advanced electron beam microscope, which was delivered to Moscow by CRDF, an American scientific fund. This tool was reconfigured by GEPD researchers into an electron beam lithography system with resolution of better than 50 nm. As the result, the technology of manufacturing of superconducting nanostructures with dimensions less than 100 nm was successfully developed. Such objects of study are the most typical in today's research in the School. The availability of such advanced equipment allows having a complete cycle of research and development entirely within the walls of Lab.
