Vol 164, No 5 (2023)

We present the experimental results of our study of the formation and dynamics of chain structures by active Brownian particles in a DC glow discharge. The mechanism of active particle motion is associated with the conversion of laser radiation by particles into the energy of their own (nonthermal) motion. Through our analysis of the motion parameters (the trajectories, the root-mean-square displacement, the kinetic energy) as a function of the intensity of laser radiation incident on the particles, we have shown that the particles are active Brownian ones. It is possible to control their motion without changing the discharge parameters. It has been experimentally found that the formation of chain structures and their stable state are not violated under kinetic heating of the particles as their kinetic energy increases by more than an order of magnitude. This suggests the realization of a mechanism for the formation of chains with a strong coupling between the particles that is not explained by the simple (ion) wake behind the upstream particle.

This paper presents an overview of Monte Carlo (MC) event generators for simulation of proton-proton collisions along with the results on hadron production at nuclotron-based ion collider facility (NICA) energies. Namely, mean multiplicities, mean transverse momenta, and rapidity distributions of p(
), π±, K± at different collision energies are presented. We also study two-particle angular correlations for stable charged particles. Results of simulations with PYTHIA, EPOS, SMASH, and UrQMD event generators are compared to available data. Connections of studied quantities with physics mechanisms in MC generators are discussed. We suggest a tuned set of parameters to address observed discrepancies between data and PYTHIA.

The Zeeman splitting in the GaAs/AlGaAs heterostructure is investigated experimentally. Numerical analysis performed for the wavefunctions of exciton states, which takes into account the bands of heavy holes, light holes, and the band split by the spin–orbit interaction, is the quantitative agreement with experimental data both for an exciton with a heavy hole and for that with a light hole. It is shown that for explaining the experimental values of the Zeeman splitting in the quantum well under investigation, it is necessary to take into account both the Coulomb interaction and the contribution from the three bands in the valence band. The effect of screening of exciton states by a 2D gas of electrons with concentration n ≈ 109 cm–2 is described. Numerical calculations are performed for a large range of quantum well widths and aluminum concentrations in barriers; the chart of the dependence of the effective g factor on these parameters is plotted for magnetic field B = 5 T.

The influence of the competition of single-ion anisotropy and easy-plane anisotropy on the magnetic properties of the multilayer structure Co/Cu/Co is investigated. The peculiarities of the influence of anisotropy effects are revealed both in the vicinity of critical temperature Tc and in the low-temperature range T < Tc. The magnetic properties of the multilayer structure are numerically simulated using the anisotropic Heisenberg model. In the vicinity of Tc, easy-plane anisotropy is shown to exert a predominant influence on the magnetic properties of the structure as compared to the influence of single-ion anisotropy. In the low-temperature range, the switching of the magnetic state of the ferromagnetic film in an external field leads to the appearance of specific features in hysteresis effects due to the competition of two types of magnetic anisotropy. The magnetic structure exhibits a size-induced transition from the behavior caused by easy-plane anisotropy to the behavior caused by single-ion anisotropy. The revealed size-induced transition is accompanied by a spin-flop effect.

In a previous report, we presented experiments which suggested that ferromagnetic ordering of the spins of localized holes in GaAs/AlGaAs quantum wells could be observed when doped with shallow (Be) acceptors at impurity concentrations near the metal-insulator transition. The compensating impurity (Si) was introduced into a narrow region at the center of the barriers [4]. In this paper, we present results from magnetotransport experiments performed on similar structures, but without the compensating impurity (Si). In these samples, the compensation degree is expected to be controlled by the background defects located at the edges of the quantum wells and within the barriers. At low temperatures T ≤ 10 K, we observed isotropic, linear magnetoresistance, anomalous behavior of the Hall effect as a function of the magnetic field, and slow relaxation of resistance after the application of a magnetic field. We explain this anomalous magnetotransport as the manifestation of a ferromagnetic transition or spin glass, originating from indirect spin exchange between localized holes on impurities near the metal-insulator transition. However, we note that perfect disorder, including signs of interspin interactions, leads to unstable configurations. In what follows, we present a model in which we start with this perfect disorder, but apply a procedure to obtain a stable configuration. We show that the resulting spin structure, a “closely packed” structure of “droplets,” can reproduce the features observed in the experiment, particularly isotropic, linear magnetoresistance.

The effect of Gaussian noise on the switching of a ZrO2(Y) based memristor from the low resistance state (LRS) into the high resistance state (HRS) including transitions from the LRS into intermediate metastable states has been studied. The series of positive (with addition of the noise signal or without the one) and negative rectangular voltage pulses were used as the switching signals. The adding of noise to the switching signal initiated the switching of the memristor from the LRS into the HRS at smaller pulse magnitudes than in the case of switching by the rectangular pulses without adding the noise. A necessary (preset) HRS can be achieved passing the intermediate states by adding the noise with certain parameters to the rectangular switching pulses. The resistive switching is performed without application of adaptive switching protocols. The results of the present study can be applied in the development of innovative memristor switching protocols.

We consider fluid flow with a free boundary, which is defined as a function of height from coordinate x with two asymptotes at positive and negative infinities (hydraulic jump). The Boussinesq approximation is used to describe the phenomenon, and an additional force is introduced. The force is chosen to depend only on the height of the surface. The problem is solved analytically without using numerical schemes. This technique is used to determine the jump surface and the acting force depending on the wave propagation coordinate.

Coupled nonlinear Schrödinger equations for paraxial optics with two circular polarizations of light in a defocusing Kerr medium with anomalous dispersion coincide in form with the Gross–Pitaevskii equations for a binary Bose—Einstein condensate (BEC) of cold atoms in the phase separation regime. In this case, the helical symmetry of an optical waveguide corresponds to rotation of the transverse potential confining the BEC. The “centrifugal force” considerably affects the propagation of a light wave in such a system. Numerical experiments for a waveguide with an elliptical cross section have revealed characteristic structures consisting of quantized vortices and domain walls between two polarizations, which have not been observed earlier in optics.