[en] An explicit analytic expression is derived for the magnetic moment of a 2D electron gas taking into account the spin-orbit interaction in the Rashba model with T = 0. The cases of constant chemical potential and number of electrons are investigated. The magnetic field and temperature dependences of the magnetic moment are analyzed. The results are compared with the results of experimental studies of magnetization

[en] An equation that describes a reflectionless propagation of non-one-dimensional relativistically strong wave packets in plasma has been studied. A family of three-dimensional solitons is found and their stability is analytically justified. The dynamics of soliton formation and their interactions have been numerically simulated

[en] The interaction of a quantized electromagnetic field in a squeezed coherent state with a three-level Λ-atom is studied numerically by the quantum Monte Carlo method and analytically by the Heisenberg-Langevin method in the regime of electromagnetically induced transparency (EIT). The possibility of noise suppression in the atomic system through the quantum properties of squeezed light is considered in detail; the characteristics of the atomic system responsible for the relaxation processes and noise in the EIT band have been found. Further applications of the Monte Carlo method and the developed numerical code to the study of more complex systems are discussed.

[en] We consider the possibility of generation of broadband terahertz (THz) radiation upon reflection of a p-polarised femtosecond laser pulse from the surface of a semi-metal. The hydrodynamic model of an instantaneous quadratic response of metals is generalised, and analytical results and numerical simulation data are presented. It is shown that transition from highly conductive metals to semi-metals is accompanied by a significant increase in the efficiency of the THz signal generation due to the reduction of the effective charge carrier mass and attenuation of the shielding of optical and THz fields. (thz radiation)

[en] The self-action dynamics of three-dimensional wave packets whose width is of the order of carrier frequency is studied under rather general assumptions concerning the dispersion properties of the medium. The condition for the wave field collapse is determined. Self-action regimes in a dispersion-free medium and in media with predominance of anomalous or normal group velocity dispersions are numerically investigated. It is shown that, for extremely short pulses, nonlinearity leads not only to the self-compression of the wave field but also to a 'turn-over' of the longitudinal profile. In a dispersionless medium, the formation of a shock front within the pulse leads to the nonlinear dissipation of linearly polarized radiation and to self-focusing stabilization. For circularly polarized radiation, the wave collapse is accompanied by the formation of an envelope shock wave

[en] We propose a new theoretical model of terahertz (THz) generation from a metal surface irradiated by femtosecond laser pulses. The mechanism is based on the inducing of the low-frequency polarization by the inhomogeneous temperature distribution of the electron gas near the surface. We present analytical and numerical results for the characteristic experimental parameters of a laser pulse. The experimentally observed duration of the THz signal (∼1 ps) is interpreted as a time of the thermal energy relaxation after the optical radiation action. The total THz energy as a function of the initial laser pulse characteristics and metal parameters is obtained. The most important experimental features are discussed and interpreted on the basis of the thermal mechanism. (paper)

[en] An analytical expression for a matrix element of the transition from a bound state of an electron in an atom to continuum states is obtained by solving the problem of interaction of the electron with a quantized electromagnetic field. This expression is used to derive formulas for the photoelectron spectrum and the rate of ionization of the simplest model atomic system upon absorption of an arbitrary number of photons. The expressions derived are analyzed and compared with the corresponding relationships obtained via other approaches. It is demonstrated that there are differences as compared to the case of the classical field. In particular, the photoelectron spectrum exhibits dips due to the destructive interference of the transition amplitudes in the quantized electromagnetic field

[en] Structural features of the laser radiation self-focusing dynamics in the electromagnetic induced transparency (EIT) band are studied for an atomic system with a Λ-type energy level diagram. Effective nonlinearity of an EIT medium is manifested primarily as nonlinear dispersion (dependence of the group velocity on the wave amplitude). Qualitative analysis of the dynamics of self-action of laser pulses, which is confirmed by numerical simulation, shows that nonlinear evolution of a 3D wave packet follows the scenario of self-focusing, which serves as the background on which the envelope profile turnover and the formation of a shock wave occur at an advanced rate

[en] Basing on the nonlinear wave equation as the reflection-free approximation, we study the self-focusing dynamics of laser pulses under rather general assumptions about media dispersion. The methods for qualitative investigation of the self-action dynamics of ultrashort pulses are developed. It is shown that a new effect here is steepening of the longitudinal pulse profile, which is determined by the dependence of group velocity on the amplitude. Results of numerical simulation in media without dispersion and with anomalous dispersion confirm the conclusion about outrunning formation of a shock wave during pulse self-focusing. The formation of a power spectrum of the field, which is characteristic for a shock wave, is retained also when medium ionization is taken into account. In the case of a normal-dispersion medium, nonlinear dispersion leads to a violation of the symmetry in the longitudinal splitting of the pulse in the process of self-focusing. The possibility of tuning of the optical-pulse frequency into the short-wave area is shown for the pulse self-action near the zero-dispersion point.

[en] A study of ‘high temperature’ entangled states in a system of two parametrically coupled quantum oscillators placed into independent thermal baths is performed taking into account partially coherent parametric pump. Processes in an open system are considered based on the Heisenberg–Langevin formalism. We obtain a closed system of equations for the averaged quadratic correlation functions in quantum stochastic problem as a result of Markov processes approximation. On the basis of numerical calculations the dynamics of the logarithmic negativity, which is the measure of entanglement in the system, is investigated. It is shown that the partial coherence of the parametric pump makes the lifetime of the entangled states finite. The threshold characteristics of the formation and existence of these states are specified. (paper)