JETP Letters最新文献

Various properties of crystal clusters (i.e., clusters consisting of particles with six nearest neighbors) in a two-dimensional Yukawa fluid have been considered for the first time in a wide temperature range beginning with the melting temperature. With increasing temperature, the concentration of crystal particles (which noticeably prevail in a melt) decreases slowly, while the defect concentration increases, which results in the formation of large clusters consisting of defects and in the degradation of large crystal clusters in the considered two-dimensional fluid. Their characteristic size and shape change sharply in a narrow temperature range. The comparative analysis of crystal clusters and clusters consisting of topological defects has been performed. Their size distributions and other structural characteristics have been obtained.

In a layer of a chiral liquid crystal with negative dielectric anisotropy and the thickness d corresponding to the second Grandjean zone ((3{{p}_{0}}{text{/}}4 < d < 5{{p}_{0}}{text{/}}4), where ({{p}_{0}}) is the natural helical pitch) under the action of a planar electric field, an orientational transition occurs from the ground state twisted by the angle (2pi ) to a topologically equivalent untwisted state (0 state). Although the 0 state is metastable and long-lived, it can rapidly be transformed back to the (2pi ) state by an electric field pulse of a comparatively small amplitude. The direct transition to the 0 state is induced by the interaction of the electric field with negative dielectric anisotropy, while the rapid reverse transition can be attributed to the flexoelectric interaction.

Models of joint random walk strategies for three parties on an infinite plane have been considered. They do not have access to communication, external landmarks, and any information about their mutual position, but can use the resource of three-particle quantum spin entanglement distributed between them within the framework of a pre-agreed protocol. Although the trajectories of the parties diverge on average, the rate of this divergence can be increased or decreased by choosing the details of the protocol.

Heterostructures with InAs/InGaAs quantum dots grown by molecular beam epitaxy on the surface of InGaAs metamorphic buffer layers with a linearly graded composition profile on GaAs(001) substrates have been studied by X-ray diffraction, transmission electron microscopy, and, upon the growth of an additional quantum-dot layer on the surface of the structure, by atomic force microscopy. The tendency to the formation of quantum objects elongated along the [1–10] direction (so-called quantum dashes), caused by asymmetry in the surface migration of In along different crystallographic directions, is confirmed. It is established that the surface density of both quantum dots and quantum dashes is as high as (2‒4) × 10¹⁰ cm^–2. At the same time, narrow lines associated with emission from individual quantum dots are observed in the spectra of low-temperature (T = 10 K) microphotoluminescence in a wide wavelength range (1.30–1.55 µm). The size and shape of quantum dots have been estimated from atomic-force microscopy and transmission electron microscopy data and good agreement with the previously reported parameters is demonstrated.

The X-ray diffraction analysis is one of the main methods to determine the structure of crystalline materials using both cw X rays and ultrashort pulses. Ultrashort pulses are usually utilized to observe dynamic processes in atomic and molecular systems. In this work, it has been shown that ultrashort pulses can have another important application in the determination of the interplanar distance between diamond layers with NV centers, which can be separated by only several angstroms. The obtained results can be extended to more complex structures and can be finally developed to a new three-dimensional tomography method with angstrom resolution.

Both Markovian and arbitrary residence time distributions are considered. The comparison of analytical predictions with the case of a time-decorrelated process shows that correlations can both decrease and increase the corresponding expected waiting time. Besides, the comparison of exponential, subexponential, and heavy-tailed models characterized by equal probabilities to observe the event of interest demonstrates that a faster decrease in the residence time probability density implies a shorter expected waiting time. Interestingly, irrespective of the details of a particular model for both discrete- and continuous-time jump processes considered here, the random waiting time becomes exponentially distributed in the long-time limit, thus, showing remarkable universality.

A mechanism of nonlinear interaction between a geodesic acoustic mode and a low-frequency zonal flow has been proposed to explain the appearance of satellites of the geodesic acoustic mode observed in tokamak experiments. Interaction between eigenmodes with significantly different frequencies leads to the modulation of the amplitude of the geodesic acoustic mode at the frequency of zonal flow oscillations, which is manifested as two side harmonics near the frequency of the geodesic acoustic mode in the spectrum of oscillations. The frequencies of the indicated harmonics correspond to the sum and difference of the frequencies of the geodesic acoustic mode and zonal flow. The effect is triggered by a stationary toroidal plasma rotation.

The possibility of applying the Marburger formula to determine the relationship between the beam power and the distance at which nonlinear collapse occurs for a beam with an initial Gaussian intensity profile and uniform elliptical polarization has been numerically investigated. It is shown that an adequate description of this relationship can be achieved by adjusting the parameters in the formula according to the ellipticity degree of the polarization ellipse of the incident radiation and the mechanism of the nonlinear optical response.

Fluorescence spectroscopy of single molecules is of fundamental significance to determine a small amount of matter and to study molecular dynamic processes. However, the applications of this method in medicine require new solutions for the miniaturization of a sensor planform. The most promising direction in this area seems to be the development of photonic integrated circuits with a high molecule detection efficiency in a volume of about cubic micron. In this work, a concept of a dielectric metalens on a waveguide, which has a high efficiency of the focusing/collection of radiation from an aqueous solution, has been presented. The structure of the metalens with a numerical aperture of above 1.1 operating in the optical range near the fluorescence maximum of the Alexa Fluor 647 dye has been simulated. After the calculation of the molecule detection efficiency, diffusion autocorrelation functions of Alexa Fluor 647 molecules have been calculated to characterize the possibility of measuring the brightness, as well as the number and dynamics of single molecules in the focal volume of the metalens. This concept provides the foundation for the development of future sensors of single molecules as biomedical and environment screening tools.

The problem of constructing universal two-nucleon momentum distributions for main NN-configurations (^{1}{{S}_{0}}) and (^{3}{{S}_{1}})–(^{3}{{D}_{1}}) used to describe short-range nucleon correlations in nuclei has been studied. A new method for calculating such distributions has been proposed, and their properties have been studied. As illustrations, calculations for several modern realistic NN potentials, including non-nucleon degrees of freedom, have been provided. A new characteristic that determines the ratio of the fractions of high-momentum components for spin-singlet and spin-triplet NN distributions at low energies, which can be useful for comparative evaluation of the isospin dependence of short-range correlations in calculations with different NN interaction potentials, has been proposed.