Electron-hole imbalance in superconductor-normal metal mesoscopic structures

We analysed the electron-hole or, in another words, branch imbalance (BI) and the related electric potential $V_{imb}$ which may arise in a mesoscopic superconductor/normal metal (S/N) structure under non-equilibrium conditions in the presence of a supercurrent. Non-equilibrium conditions can be created in different ways: a) a quasiparticle current flowing between the N reservoirs; b) a temperature gradient between the N reservoirs and no quasiparticle current. It is shown that the voltage $V_{imb}$ oscillates with the phase difference $\phi$. In a cross-geometry structure the voltage $V_{imb}$ arises in the vertical branch and affects the conditions for a transition into the $\pi$-state.Comment: 6 pages, 5 figures, accepted for publication in Europhysics Letter

Stimulated emission and lasing in Cu(In,Ga)Se2 thin films

Stimulated emission and lasing in Cu(In,Ga)Se 2 thin films have been demonstrated at a temperature of 20 K using excitation by a nanosecond pulsed N 2 laser with power densities in the range from 2 to 100 kW cm − 2 . Sharp narrowing of the photoluminescence band, superlinear dependence of its intensity on excitation laser power, as well as stabilization of the spectral position and of the full-width at half-maximum of the band were observed in the films at increasing excitation intensity. The stimulated emission threshold was determined to be 20 kW cm − 2 . A gain value of 94 cm − 1 has been estimated using the variable stripe length method. Several sharp laser modes near 1.13 eV were observed above the laser threshold of I thr ~ 50 kW cm −

Nonlinear effects in microwave photoconductivity of two-dimensional electron systems

We present a model for microwave photoconductivity of two-dimensional electron systems in a magnetic field which describes the effects of strong microwave and steady-state electric fields. Using this model, we derive an analytical formula for the photoconductivity associated with photon- and multi-photon-assisted impurity scattering as a function of the frequency and power of microwave radiation. According to the developed model, the microwave conductivity is an oscillatory function of the frequency of microwave radiation and the cyclotron frequency which turns zero at the cyclotron resonance and its harmonics. It exhibits maxima and minima (with absolute negative conductivity) at the microwave frequencies somewhat different from the resonant frequencies. The calculated power dependence of the amplitude of the microwave photoconductivity oscillations exhibits pronounced sublinear behavior similar to a logarithmic function. The height of the microwave photoconductivity maxima and the depth of its minima are nonmonotonic functions of the electric field. It is pointed to the possibility of a strong widening of the maxima and minima due to a strong sensitivity of their parameters on the electric field and the presence of strong long-range electric-field fluctuations. The obtained dependences are consistent with the results of the experimental observations.Comment: 9 pages, 6 figures Labeling of the curves in Fig.3 correcte

Temperature dependence of AgIn13S20 single crystal band gap

AgIn13S20 single crystals were grown by the vertical Bridgman method. The grown crystals composition was determined by X-ray spectroscopy analysis; the crystal structure was determined by X-ray method. It was shown, that AgIn13S20 compound crystallize in the cubic spinel structure. The band gaps of the obtained single crystals were estimated from transmittance spectra in the temperature range of 10-320 K. The band gap values decreased with temperature

Stimulated emission and optical properties of solid solutions of Cu(In,Ga)Se2 direct band gap semiconductors

Stimulated emission, optical properties, and structural characteristics of non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films deposited on soda lime glass substrates using co-evaporation of elements in a multistage process were investigated. X-ray diffraction analysis, scanning electron microscopy, X-ray spectral analysis with energy dispersion, low-temperature photoluminescence, optical transmittance and reflectance were used to study the films. Stimulated emission at low temperatures of ~20 K was found in non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films upon excitation by laser pulses of nanosecond duration with a threshold power density of ~20 kW/cm2. It was shown that the appearance and parameters of the stimulated emission depend strongly on the concentration of ion-induced defects in Cu(In,Ga)Se2 thin films

Photoluminescence, Stimulated and Laser Emission in CuInSe2crystals

Excitonic quality CuInSe2 crystals were studied using low-temperature (10 K) photoluminescence (PL) excited by continuous wave and nanosecond pulsed lasers at power densities from 0.01 to 76 kW/cm2. Increasing the excitation power density level to 26 kW/cm2 resulted in the appearance of a stimulated emission SE-band in the PL spectra at 1.035 eV. Further increase in the excitation level to 39 kW/cm2 generated on the top of the SE band, a structure of equidistant sharp lines attributed to laser emission. © 2021 Author(s).This work was supported by State Program of Scientific Research of the Republic of Belarus “Physical Material Science, New Materials and Technologies” (Project No. 1.4.4) and Belarusian Republican Foundation of Basic Research (Grant No. F20M-058). The research was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation (“Spin” No. AAAA-A18-118020290104-2)

Observational Constraints on the Common Envelope Phase

The common envelope phase was first proposed more than forty years ago to explain the origins of evolved, close binaries like cataclysmic variables. It is now believed that the phase plays a critical role in the formation of a wide variety of other phenomena ranging from type Ia supernovae through to binary black holes, while common envelope mergers are likely responsible for a range of enigmatic transients and supernova imposters. Yet, despite its clear importance, the common envelope phase is still rather poorly understood. Here, we outline some of the basic principles involved, the remaining questions as well as some of the recent observational hints from common envelope phenomena - namely planetary nebulae and luminous red novae - which may lead to answering these open questions.Comment: 29 pages, 8 figures. To appear in the book "Reviews in Frontiers of Modern Astrophysics: From Space Debris to Cosmology" (eds. Kabath, Jones and Skarka; publisher Springer Nature) funded by the European Union Erasmus+ Strategic Partnership grant "Per Aspera Ad Astra Simul" 2017-1-CZ01-KA203-03556

Study on metabolic status of tear fluid in hypothyroidism patients with dry eye syndrome

Introduction. Dry eye syndrome (DES) is associated with a complicated multifactorial mechanism, the peculiarities of which are being studied at the moment. Data on tear production disorders in hypothyroidism and on disturbances in activity of enzymes providing homeostasis of reduced glutathione in DES underline the need to study metabolic alterations in lacrimal gland function in patients with hypothyroidism. Purpose. To study the character of metabolic alterations in the tear fluid in primary hypothyroidism patients with DES. Material and Methods. We examined 78 patients with primary hypothyroidism. Among the patients, there were 16 subclinical hypothyroidism patients without DES (hypothyroidism-only group) and 62 patients with DES (hypothyroidism+DES group) (hypothyroidism type: subclinical, 32 patients; manifest, 30 patients; hypothyroidism compensation: compensation, 28 patients; subcompensation, 20 patients; decompensation, 14 patients). 16 healthy volunteers served as controls. Results. Hypothyroidism patients had more pronounced biochemical changes in the tear fluid in manifest hypothyroidism with DES and decompensated hypothyroidism: the increased activity of acid phosphatase, lactate dehydrogenase, and malate dehydrogenase; disorders in the thiol status against the background of the increased malondialdehyde level. Conclusions. The increased activity of dehydrogenases and acid phosphatase as well as of malondialdehyde against the background of the decreased thiol status in the tear fluid can testify to destruction in cells and subcellular structures of the corneal epithelium in hypothyroidism accompanied with DES that is caused by the action of both lipid peroxidation products and lysosomal enzymes