Vol 123, No 1 (2016)

The setting time of the stationary distribution over translational degrees of freedom of two-level atoms in the field of a one-dimensional standing light wave is studied. The dependences of this time on the problem parameters such as the light wave intensity, frequency detuning, and atom mass are obtained. Calculations are performed on the basis of the quantum-mechanical equation for the atomic density matrix taking completely into account the recoil and spatial localization effects in an arbitrarily intense light field.

We study an excitation of surface plasmons (SPs) due to the scattering of light by a dipole nanoparticle located near a flat air–metal interface. It is well known that such a scattering can reveal asymmetric behavior of excited SPs with respect to the plane of incidence of light. This asymmetric SP excitation, which takes place at the incidence of elliptically polarized light, is often associated with the so-called photonic spin Hall effect caused by the interplay between rotating polarization of a nanoparticle and the intrinsic field angular momentum of the SP. We show that this photonic spin Hall effect can be applied for the SP excitation control, which allows managing the SP directivity pattern and amplitude. The possibilities of SP control can also be extended using nanoparticles with anisotropic polarizability. We believe that manipulations with SPs at a nanometer scale may find some applications in modern nanoplasmonics.

The local electronic structure of copper ions in a copper metaborate CuB₂O₄ crystal is studied on the ESRF synchrotron using X-ray absorption polarization-dependent spectroscopy. The X-ray natural circular dichroism near the K absorption edge of copper is measured in the direction that is perpendicular to crystal axis c. The data obtained indicate the presence of hybridized p–d electronic states of copper. Theoretical calculations are used to separate the contributions of the two crystallographically nonequivalent positions of copper atoms in the unit cell of CuB₂O₄ to the absorption and X-ray circular dichroism spectra of the crystal.

The aim of this paper is to explore warm inflation in the background of f(G) theory of gravity using scalar fields for the FRW universe model. We construct the field equations under slow-roll approximations and evaluate the slow-roll parameters, scalar and tensor power spectra and their corresponding spectral indices using viable power-law model. These parameters are evaluated for a constant as well as variable dissipation factor during intermediate and logamediate inflationary epochs. We also find the number of e-folds and tensor- scalar ratio for each case. The graphical behavior of these parameters proves that the isotropic model in f(G) gravity is compatible with observational Planck data.

We have proposed a mechanical model that corresponds to the Newton equation for describing the dynamics of an oscillon, viz., a soliton-like cluster of the Bose–Einstein condensate (with atomic attraction) placed above an oscillating atomic mirror in a uniform gravitational field. The model describes the stochastic Fermi acceleration and periodic, quasi-periodic, and chaotic motion of the oscillon center, as well as hysteresis phenomena in the case of a slow variation of mirror oscillation frequency, which are in good agreement with the results obtained using the Gross–Pitaevskii equation.

The theory of multiband superconducting systems with variable density of charge carriers is analyzed. The possibility of emergence of nonphonon high-temperature superconductivity due to the predominance of electron–electron interband interactions over intraband interactions, as well as due to the fact that the thermodynamic and magnetic properties of multiband systems in the superconducting phase differ qualitatively from those of single-band systems, is indicated. Phase transitions in a quasi-2D anisotropic medium upon a change in the carrier concentration, i.e., a transition from the commensurate to the incommensurate state of the spin density wave, are analyzed. Such a transition is observed when the Umklapp processes in the lattice structure are taken into account. These processes facilitate a deviation of wavevector Q of the spin density wave from 2k_F, as well as a displacement of the bandgap relative to the Fermi surface. This leads to the generation of free charge carriers and the possibility of superconductivity. It is shown that superconductivity accompanies the magnetism. The conditions for the coexistence of these two phenomena are determined.

The dynamic behavior of a domain wall with cross-ties is analyzed on the basis of micromagnetic simulation with exact allowance for all main (exchange, magnetoanisotropic, and magnetostatic) interactions in thin magnetically uniaxial ferromagnetic films with planar anisotropy. It is found that the peculiarities of motion of such domain walls are closely related to the behavior of topological defects in the magnetization distribution (generation, motion, and annihilation of vortex–antivortex pairs on the film surface and Bloch points). We observe three different regimes of motion (stationary, periodic, and turbulent regimes), each of which is realized in a certain range of fields oriented along the easy magnetization axis. It is shown that the experimentally observed dynamic bends of the walls with cross-ties are determined by the type of motion of vortices and antivortices. The velocities of domain walls in different regimes are calculated, and the dynamic configurations of the magnetization and existing dynamic transitions between them are investigated.

New composite materials (SrFe₁₂O₁₉)_x(CaCu₃Ti₄O₁₂)_1–x (x = 0, 0.05, 1) have been synthesized. Their magnetic properties are studied in the temperature range 5–300 K using the magnetic resonance and magnetometry methods. It is found that strontium hexaferrite microinclusions in the (SrFe₁₂O₁₉)_0.05(CaCu₃Ti₄O₁₂)_0.95 composite “magnetize” CaCu₃Ti₄O₁₂ at temperatures from 300 to 200 K, forming a ferrimagnetic particle near the SrFe₁₂O₁₉ “core.” The magnetic resonance line below 200 K splits into two lines corresponding to SrFe₁₂O₁₉ and CaCu₃Ti₄O₁₂. The core effect decoration is manifested in the increase in the Curie–Weiss temperature from 25 K in CaCu₃Ti₄O₁₂ without the doping ceramics to 80 K in the composite with 5% of SrFe₁₂O₁₉.

We report the results on the measurements of the work function of single-walled carbon nanotubes encapsulated by Agl (AgI@SWCNT), AgCl (AgCl@SWCNT), and CuBr (CuBr@SWCNT) by the local Kelvin probe technique. We found the values of the work function of tubes encapsulated with AgI and AgCl (Φ(AgI@SWCNT) = 5.08 ± 0.02, Φ(AgCl@SWCNT) = 5.10 ± 0.02 eV) to exceed substantially that of pristine carbon nanotubes, and the value of the work function of carbon nanotubes encapsulated with CuBr is Φ(CuBr@SWCNT) = 4.89 ± 0.03 (eV). The measurements are carried out using different kinds of microscope probes including multi-walled carbon nanotube tips.

We analyze the effect of magnetic breakdown on the resistance of layered organic conductors with a multisheet Fermi surface consisting of a cylinder and two slightly corrugated planes along the projection of the momentum onto the normal to the layers. Analytic expressions are derived for the charge carrier distribution function, and the dependences of the interlayer and intralayer conductivities on the magnitude and orientation of the external magnetic field in the immediate vicinity of a topological phase transition are determined when the distance between the different sheets of the Fermi surface is quite small, but the topological structure of the Fermi surface is still intact.