Investigation of the structure and phase composition of Cu-Si films obtained by ion beam sputtering
Investigation of the structure and phase composition of Cu-Si films obtained by ion beam sputtering
E. S. Kersnovsky, I. V. Polshin, K. A. Barkov, D. N. Nesterov, S. A. Ivkov, V. A. Terekhov, B. L. Agapov, A. V. Sitnikov
In this work, the structure, phase composition and electronic structure of Cu-Si films with different copper content (from 15 to 68 wt.%) obtained by ion beam sputtering were studied by X-ray diffraction and ultra-soft X-ray emission spectroscopy. It was found that when Cu-Si films have a low copper content (~15 wt.%), the phases of 𝝲-Cu5Si and amorphous silicon a-Si are formed. Increasing the Cu content to up to 68 wt.% leads to the formation of the phases 𝞰-Cu3Si and 𝞰''-Cu3Si, as well as partial oxidation of copper with the formation of Cu2O oxide, while significant changes in the electronic structure of the valence band are observed as a result of the interaction of copper d-electrons and silicon s,p-electrons. An increase in the copper content in the composition of Cu-Si films from ~15 wt.% to ~68 wt.% is accompanied by a decrease in resistivity from ~1*10-3 to ~3*10-4 ohms *cm.
Show AbstractDecoherence of neutrino oscillations in a magnetic field due to wave packets separation
Decoherence of neutrino oscillations in a magnetic field due to wave packets separation
A. R. Popov$^1$, A. I. Studenikin$^2$
Neutrino oscillations in a magnetic field considered within the formalism of wave packets. Damping of neutrino oscillations in a magnetic field due to neutrino wave packets separation is studied. The expressions for neutrino oscillations probabilities in a magnetic field accounting for decoherence effects are obtained. It is shown that the coherence lengths of oscillations on magnetic frequencies are proportional to the cube of neutrino energy. The obtained results are of interest for neutrino telescopes IceCube, Baikal-GVD and KM3NeT, and also can be applied for description of supernovae neutrino oscillations effects would be detected by JUNO, Hyper-Kamiokande and DUNE.
Show AbstractModel of polymer destruction under the action of superthermal atomic oxygen
Model of polymer destruction under the action of superthermal atomic oxygen
N. P. Chirskaya$^1$, E. N. Voronina$^{1,2}$, L. S. Novikov$^1$
This work examines existing approaches to simulation of polymer materials destruction processes under the action of superthermal oxygen atoms with respect to the conditions of the near-Earth space. The parameters of the reactions between hyperthermal oxygen atoms and a polyimide monomer, leading to the formation of volatile products such as CO2, CO and OH have been calculated using the density functional based tight-binding (DFTB) method and molecular dynamics method. The parameters obtained with two methods were compared.
Show AbstractLight hypernuclei near the neutron drip line
Light hypernuclei near the neutron drip line
A. S. Kornilova$^1$, S. V. Sidorov$^2$, D. E. Lanskoy$^1$, T. Yu. Tretyakova$^{1,2}$
Addition of a Λ-hyperon to non-strange nuclei can result in an increase of binding energy and formation of bound hypernuclei with unbound nucleon cores, effectively shifting the nucleon drip lines on the hypernuclear chart. The structure of light neutron-rich hypernuclei is treated within the Hartree-Fock approach with potentials in the Skyrme form. We show that nuclei 10Li is likely bound by a Λ-hyperon, while adding the hyperon to 9He and 10He does not bind them.
Show AbstractElectronic transport via localized states in Keldysh non-equilibrium diagram technique
Electronic transport via localized states in Keldysh non-equilibrium diagram technique
I. D. Kopchinskii, V. V. Shorokhov
Keldysh non-equilibrium diagram technique is used for a detailed description of electronic transport through a system of localized states. Particular attention is paid to the predictive ability of the theory, for which the number of free parameters in the second-quantized Hamiltonian is reduced. The employed formalism accounts for Coulomb interaction and rigorously treats multi-electron effects and the discreteness of the energy spectra of such structures as induced quantum dots, systems of impurity atoms, or charge centers of metal-organic framework polymers. The proposed algorithm for calculating electric currents and occupation numbers of localized states is implemented in software and tested on a model system with two consecutive two-level quantum dots. The calculated volt-ampere characteristic and current stability diagram are intuitively explained using illustrative energy diagrams. The model successfully reproduces typical single-electron effects: resonant tunneling, negative differential resistance, population inversion in a multilevel system, Coulomb correlations and an indirect manifestation of the memory effect.
Show AbstractA.G. Sveshnikov's works in the numerical methods for the irregular waveguides design
A.G. Sveshnikov's works in the numerical methods for the irregular waveguides design
A. A. Bykov
In a series of works by Professor A.G.Sveshnikov in 1963 a mathematical model of the propagation of electromagnetic waves inside a metal waveguide with a complex shape boundary was formulated. This model is based and substantiated on the modified Galerkin method. Later it was named al the incomplete Galerkin method. The solution of the boundary value problem is presented in the form of a linear combina-tion of coordinate functions of the cross-section, the complete set of which is found from the eigenvalues-eigenvectors-problem inside the cross-section of the waveguide. The coefficients of the linear combination depend on the longitudinal coordinate. They are found from the condition of orthogonality of the discrep-ancy to the system of projection functions. In case of the Galerkin method, the set of the projection func-tions is equal to the set of coordinate functions (also cross-section depended). A boundary value problem for a system of linear ordinary differential equations of the second order is obtained as the result of the application of projection relations of orthogonality and boundary conditions of radiation in infinite re-gions. We show that the method created 60 years ago at the Department of Mathematics of the Faculty of Physics of Moscow State University is still relevant today. The increased capabilities of computers, math-ematical and programming tools make it possible to significantly expand the class of problems that are effectively solved using the incomplete Galerkin method. We present the results of solving one problem of optimizing a waveguide transformer in a loaded waveguide using an incomplete Galerkin method.
Show AbstractStatistical characteristics of the current flowing through semiconductor superlattice, with structure fluctuations
Statistical characteristics of the current flowing through semiconductor superlattice, with structure fluctuations
A. О. Selskii, O. I. Moskalenko, A. A. Koronovskii
The paper investigates how fluctuations in the lattice structure, namely the width of the conducting miniband, affect the current flowing through a semiconductor superlattice. To solve this problem, a numerical calculation model is proposed that makes it possible to calculate the current for random changes in the miniband width in the superlattice layers, both in the case of an inclined magnetic field and without it. In order to evaluate the change in current, two integral characteristics were introduced: one for the shape of the current-voltage characteristic, the second for the amplitude of high-frequency current oscillations. The integral characteristics ranked in ascending order make it possible to approximately approximate the variability of the characteristics of the current flowing through a semiconductor superlattice for various fluctuations of the lattice structure.
Show AbstractStatistical analysis of the characteristics of recurrent analysis of various stages of sleep
Statistical analysis of the characteristics of recurrent analysis of various stages of sleep
A. О. Selskii$^{1,2}$, M. О. Zhuravlev$^{1,2}$, M. Yu. Novikov$^1$, A. E. Runnova$^1$
This article discusses the statistical analysis of recurrent indicators calculated for different stages of sleep in three groups of subjects: healthy people, with Parkinson's disease, and with sleep apnea. Statistical analysis included the calculation of recurrent indicators and parameters associated with the estimation of the spread of recurrent indicators for sleep stages compared with the average value for this stage and for the entire night recording. It has been shown that for patients with Parkinson's disease, the spread of the recurrent indicator for the wakefulness stage is extremely large, which makes further analysis difficult, but can be a good biomarker for early recognition of the disease. For apparently healthy subjects and patients with sleep apnea, sleep stages 3 and 4 differ most from the overnight averages, but have the smallest deviations from the average for this stage. Patients with sleep apnea have a higher dispersion for REM sleep compared to healthy subjects.
Show AbstractAlgorithm for determining the optical profile of thin gradient-index films via surface plasmon resonance
Algorithm for determining the optical profile of thin gradient-index films via surface plasmon resonance
A. V. Anisimov, S. A. Lobastov, I. S. Khasanov
This work details the physical and mathematical foundations of an algorithm to determine the optical profile of thin gradient films using the surface plasmon resonance (SPR) method. The algorithm minimizes the discrepancy function, which quantifies the deviation between experimental data and model data of the targeted gradient layer, approximated using a cubic Hermite interpolant known as PCHIP. Powell's method optimization, implemented in Python, determines the optimal coordinates for the spline nodes approximating the gradient optical layer. To enhance stability, accuracy, and search speed, the algorithm operates in three stages. Each stage refines the search area and sets initial parameters for the subsequent stage to align closely with the targeted gradient layer. The algorithm incorporates angle, wavelength, and external environment scan data derived via SPR.
Show AbstractCorrection of recurrent analysis taking into account the frequency of the EEG signal on the example of processing cognitive tests of patients with migraine
Correction of recurrent analysis taking into account the frequency of the EEG signal on the example of processing cognitive tests of patients with migraine
E. P. Emelyanova$^1$, A. О. Selskii$^{1,2}$, A. E. Runnova$^{1,2}$
Recurrent analysis is a good correlation method of processing EEG data of the human brain. It is aimed at identifying links between channels. In particular, the modified recurrent analysis is designed to identify the most significant channels with a certain activity. At the same time, recurrent analysis is a method that strongly depends on frequency. The paper proposes a method for correcting the results obtained by recurrent analysis of the EEG processing of the brain data of the subjects, taking into account the frequency based on the Fourier transform.
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