


Vol 117, No 11-12 (6) (2023)
Articles
Measurement of the T20 Component of the Tensor Analyzing Power of the Incoherent Photoproduction of a π– Meson on a Deuteron
Abstract
New results have been presented for the T20 component of the tensor analyzing power of the γd → ppπ– reaction measured in the photon energy range from 300 to 600 MeV. The data have been obtained from the statistical sample collected at the VEPP-3 accelerator in 2021. The T20 component has been separated using the asymmetry of the reaction yield, which is due to change in the sign of the tensor polarization of the deuterium target. The experimental data have been compared to the simulation within the spectator model including the interaction between particles in the final state.



Towards -Symmetric Optical Dimer Fabrication without a Light-Absorbing Material
Abstract
We consider an approach to engineer an optical dimer of particles operating in the spectral region near the dipolar resonance that exhibits parity–time symmetry-like features. Both particles are assumed to be made of a gain medium with the same refractive index and extinction coefficient. We suggest introducing a gain–loss contrast by altering the radiative loss of the particles through changing their shape. To demonstrate our approach, we consider a dimer of infinite filled and hollow cylinders. We demonstrate that a larger hollow diameter leads to a stronger radiative decay. Then we find the parameters of a dimer that has an exceptional point at a real frequency and exhibits two real eigenfrequencies when the gain–loss contrast is decreased.



Ultrathin GeTe Crystal in a Strong Femtosecond Laser Field: Manifestation of a Quantum Size Effect
Abstract
The behavior of a thin-film GeTe crystal induced by intense femtosecond laser pulses (μm) has been studied using a pulsed electron diffractometer. The sample is an annealed 20-nm GeTe film on a copper grid with a carbon coating. It has been found that laser ablation results in the formation of an ultrathin GeTe crystal (assumingly, GeTe monolayer) with a high radiation resistance. Possible reasons for the detected nanosize effect are discussed.



Random Laser Based on Materials in the Form of Complex Network Structures
Abstract
The theory of a random laser with an interface in the form of random or scale-free networks whose nodes are occupied by microcavities with quantum two-level systems has been proposed for the first time. The microcavities are coupled to each other through light-guiding channels forming edges of the network. It has been shown that such a laser has a number of spectral features associated with the statistical properties of the network structure. Among them are the existence of a topologically protected Perron eigenvalue caused by the presence of a strong mean field at the node of maximum influence located in the central part of the network and the delocalization/localization of radiation modes depending on the probability of coupling between arbitrary microcavities. The results obtained in this work open prospects for the fabrication of new low-threshold laser sources.



Designing the Structure of a One-Dimensional Photonic Crystal with a Given Spectrum of the Reflection Coefficient
Abstract
A method for solving the inverse problem of designing the structure of a one-dimensional photonic crystal is proposed and experimentally implemented. It is known that a one-dimensional photonic crystal with a spatial sinusoidal modulation of the refractive index, has a narrow photonic bandgap at a frequency related to the spatial frequency of this sinusoid. A reverse engineering method is proposed for one-dimensional photonic crystals with an arbitrary given reflection spectrum by expanding this spectrum into elementary photonic band gaps and then summing them. The application of this method to fabricate examples of photonic crystals with simple shapes of spectral reflection curves is demonstrated.



Inverse Faraday Effect in Superconductors with a Finite Gap in the Excitation Spectrum
Abstract
The inverse Faraday effect (generation of a time-independent magnetic moment under the action of a circularly polarized electromagnetic wave) in mesoscopic superconducting samples with a finite gap in the excitation spectrum is analytically described. Within the modified time-dependent Ginzburg–Landau theory (Kramer–Watts-Tobin equations) for thin superconducting disks, it is shown that the temperature dependence of the optically induced magnetic moment is nonmonotonic in a wide range of parameters and contains a maximum. This maximum is due to the dephasing between the spatial oscillations of the magnitude and the phase of the order parameter, which arises with a decrease in the temperature and, correspondingly, in the characteristic relaxation time of perturbations in the superconducting condensate.



Mysteries of Water and Other Anomalous Liquids: “Slow” Sound and Relaxing Compressibility and Heat Capacity (Brief Review)
Abstract
Reasons for the existence of “fast” sound at terahertz frequencies in various liquids have been analyzed. It has been shown that the fast sound speed is described well by the conventional formula from the theory of elasticity
, where ρ is the density of a liquid and
and
are the bulk and shear moduli at the frequency ω, respectively. The excess of the speed of fast sound over the speed of normal sound in “normal” liquids is 10–20% and is almost completely determined by the contribution of the shear modulus
at high frequencies, and vanishes on the Frenkel line. At the same time, the huge excess (50–120%) of the fast speed of sound over the speed of normal sound in some liquids (called “anomalous”), such as water and tellurium melt, is due mainly to the strong frequency dependence of the bulk modulus
. Anomalously low relaxing bulk moduli were studied in our previous works for many oxide and chalcogenide glasses near smeared pressure-induced phase transitions. In anomalous liquids, smeared phase transitions also occur in a wide temperature and pressure region, which sharply reduces the bulk moduli and speeds of sound. Thus, the record large difference between speeds of fast and normal sound in anomalous liquids is due not to anomalously fast sound but to the fact that normal sound in such liquids is anomalously “slow” and bulk moduli are anomalously low. Ultrasonic studies of low- and high-density amorphous water ices show that their bulk moduli are indeed a factor of 4–5 higher than the bulk modulus of water. In addition, because of smeared phase transitions, the heat capacities of water and tellurium melt are a factor of 1.5–2 higher than those for normal liquids; i.e., anomalous liquids are characterized not only by an anomalous (nonmonotonic) behavior but also by anomalous magnitudes of physical quantities for most of the available measurement methods. A similar anomalous increase in the compressibility and heat capacity is observed for all fluids in the close vicinity of the liquid–gas critical point. In this case, anomalously fast sound is observed at terahertz frequencies, which is also due to a sharp increase in the bulk modulus
at high frequencies. At the same time, high compressibility and heat capacity, as well as a large excess of the speed of fast sound over the speed of normal sound, for anomalous liquids and glasses near smeared phase transitions are not necessarily due to the proximity of critical points and occur in any scenario of the smeared phase transition.



Polarons and Charge Transfer in FeCr2O4 Chromite Treated by the DFT + U Method
Abstract
The electronic structure of chromite (FeCr2O4 spinel) is described and the orbital ordering, band gap, and charge transfer are analyzed consistently in the framework of density functional theory taking into account strong electron correlations (DFT + U method). It is shown that the top of the chromite valence band in this model is formed by the ordered t2g orbitals of iron atoms located at tetrahedral sites, and the formation of hole polarons occurs involving just these orbitals. The nonadiabatic activation barrier determining the hole polaron transport is considered. The results of calculations of the band gap and activation energy are compared to the available experimental data.



Electron correlation e ects in paramagnetic cobalt
Abstract
We study the influence of Coulomb correlations on spectral and magnetic properties of fcc cobalt using a combination of density functional theory and dynamical mean-field theory. The computed uniform and local magnetic susceptibilities obey the Curie–Weiss law, which, as we demonstrate, occurs due to the partial formation of local magnetic moments. We find that the lifetime of these moments in cobalt is significantly less than in bcc iron, suggesting a more itinerant magnetism in cobalt. In contrast to the bcc iron, the obtained electron self-energies exhibit a quasiparticle shape with the quasiparticle mass enhancement factor m*/m ~ 1.8, corresponding to moderately correlated metal. Finally, our calculations reveal that the static magnetic susceptibility of cobalt is dominated by ferromagnetic correlations, as evidenced by its momentum dependence.



Robust and fast quantum state transfer on superconducting circuits
Abstract
Quantum computation attaches importance to high-precision quantum manipulation, where the quantum state transfer with high fidelity is necessary. Here, we propose a new scheme to implement the quantum state transfer of high fidelity and long distance, by adding on-site potential into the qubit chain and enlarging the proportion of the coupling strength between the two ends and the chain. In the numerical simulation, without decoherence, the transfer fidelities of 9 and 11 qubit chain are 0.999 and 0.997, respectively. Moreover, we give a detailed physical realization scheme of the quantum state transfer in superconducting circuits, and discuss the tolerance of our proposal against decoherence. Therefore, our scheme will shed light on quantum computation with long chain and high-fidelity quantum state transfer.



Implementation of a Quantum Memory Protocol Based on the Revival of Silenced Echo in Orthogonal Geometry at the Telecommunication Wavelength
Abstract
An optical quantum memory protocol has been implemented on the basis of the revival of silenced echo at the telecommunication wavelength for signal light fields with a small number of photons. To this end, a long-lived (>1 s) absorption line has been initialized and the orthogonal geometry of the propagation of the signal and rephasing fields has been chosen. An efficiency of revival of (17 ± 1)% has been reached for the orthogonal polarization components of a signal pulse at a storage time of 60 μs. The input pulse contains ~38 photons on average, the revived echo signal includes ~6 photons, and the signal-to-noise ratio is 1.3.



Use of a Fluorescent Dye for Controlling the Laser Absorption in the Femtosecond Laser Nanosurgery of Cells
Abstract
The use of specific fluorescent dyes is able to reduce the labeled cell structure ionization threshold under the femtosecond laser impact. This feature may be applied in terms of the laser nanosurgery of the cell. In this work we use BioTracker Blue dye as a photosensitizer in order to receive an accurate control of cytoplasmic membrane ablation by femtosecond laser and to relief the laser-induced cell fusion. We have found that BioTracker Blue (366/441) increases an efficiency of the 760 and 730 nm laser absorption. However, an increase of absorption efficiency, provided by the BioTracker Blue staining, did not improved the efficiency of the cell fusion in the model systems: pairs of suspended A549 cells, oocytes and their polar bodies, and two-cell embryos.



Elastic neutrino-atom scattering as a probe of neutrino millicharge and magnetic moment
Abstract
Neutrino scattering on a target at low-energy transfer is one of the basic tools for searching for neutrino electromagnetic properties. We consider the effects of the neutrino millicharge and magnetic moment on the atomic recoil spectrum in elastic neutrino–atom scattering. The results of our calculations of differential cross sections for elastic collisions of tritium neutrinos with the H, 2H, 3He, and 4He atomic targets show that the corresponding experiments can achieve sensitivity to the indicated neutrino electromagnetic characteristics by orders of magnitude better than the available measurements of elastic neutrino–electron and neutrino–nucleus collisions.



Energy Spectrum of β Electrons in Neutrinoless Double-β Decay Including the Excitation of the Electron Shell of Atoms
Abstract
Double-β decay is accompanied with a high probability by the excitation of the electron shell of the daughter atom; as a result, the energy carried away by β electrons decreases. The mean value and standard deviation of the excitation energy of the electron shell of the daughter atom in the double-β decay of germanium
have been determined within the Thomas–Fermi and relativistic Dirac–Hartree–Fock methods. Using the estimates thus obtained, a two-parameter model of the energy spectrum of β electrons in the neutrinoless mode has been developed including the redistribution of the reaction energy between the decay products. The shift of the total energy of β electrons does not exceed 50 eV with a probability of 90%. However, the mean excitation energy is ~400 eV, i.e., an order of magnitude higher, whereas the standard deviation is ~2900 eV, which is apparently due to a significant contribution from inner electron levels to the energy characteristics of the process. The distortion of the shape of the peak of the 0ν2β decay should be taken into account when analyzing the data of detectors with a resolution of ~100 eV or higher.



Light-shining-through-wall cavity setups for probing alps
Abstract
We discuss the aspects of axion-like-particles searches with Light-Shining-through-Wall experimental setups consisted of two radio-frequency cavities. We compare the efficiencies of four setups which involve the cavity pump modes and external magnetic fields. Additionally, we discuss the sensitivity dependence both on the relative position of two cylindrical cavities and on their radius-to-length ratio.



Gluon Anomaly and the Violation of the Zweig Rule
Abstract
It is well known that the gluon anomaly is responsible for the mass of the U(1) Goldstone boson. It is also manifested in the properties of pseudo-Goldstone states: the gluon anomaly in the next order of the 1/Nc expansion induces interactions violating the Zweig rule. A necessary condition for this is the explicit breaking of the chiral symmetry by the masses of light quarks. One of the physical consequences is that the η–η' mixing does not affect the
amplitude. Another consequence is the suppression of the first 1/Nc correction to the η–η' mixing angle. The mechanism of such suppression is discussed in detail. The conclusions are based on the 1/Nc expansion and the effective meson Lagrangian of the Nambu–Jona-Lasinio model and are compared with the results of the 1/Nc chiral perturbation theory.



Natural Explanation of Recent Results on e+e- → λλ¯
Abstract
We show that the recent experimental data on the cross section of the process e+e- ΛΛ¯ near the threshold can be perfectly explained by the final-state interaction of Λ and Λ¯. The enhancement of the cross section is related to the existence of low-energy real or virtual state in the corresponding potential. We present a simple analytical formula that fits the experimental data very well.



Inclusion of the Energy Distribution of Free Carriers in the Rate Equations Describing Their Dynamics at the Interaction of Dielectrics with Intense Laser Radiation
Abstract
The dynamics of free carriers in CaF2 induced by intense femtosecond radiation of the near- (1.24 μm) and mid- (4.4 μm) infrared ranges has been studied. It has been shown that the energy distribution of carriers formed after the passage of a laser pulse with a fluence sufficient for active impact ionization has a shape independent of the parameters (fluence, duration, and wavelength) of laser radiation and the width of the band gap of the material. The mean kinetic energy of free carriers after the action of the pulse is 0.56 of the width of the band gap. The inclusion of the dispersion term in rate carrier dynamics models makes it possible to reduce the difference of the mean kinetic energy from the statistical Fokker–Planck model by 30%. The application of rate carrier dynamics models instead of statistical models requiring large time and computational resources allows one to accelerate calculations by a factor of 20.



Energy Spectrum of the Valence Band in HgTe Quantum Wells on the Way from a Two- to Three-Dimensional Topological Insulator
Abstract
The magnetic field and temperature dependences of longitudinal magnetoresistance and the Hall effect have been measured in order to determine the energy spectrum of the valence band in HgTe quantum wells with the width dQW = 20–200 nm. The comparison of hole densities determined from the period of Shubnikov–de Haas oscillations and the Hall effect shows that states at the top of the valence band are doubly degenerate in the entire dQW range, and the cyclotron mass
determined from the temperature dependence of the amplitude of Shubnikov–de Haas oscillation increases monotonically from
to
(
is the mass of the free electron) with increasing hole density
from
to
cm–2. The determined dependence has been compared to theoretical dependences
calculated within the four-band kP model. These calculations predict an approximate stepwise increase in
owing to the pairwise merging of side extrema with increasing hole density, which should be observed at
and 4 × 1010 cm–2 for dQW = 20 and 200 nm, respectively. The experimental dependences are strongly inconsistent with this prediction. It has been shown that the inclusion of additional factors (electric field in the quantum well, strain) does not remove the contradiction between the experiment and theory. Consequently, it is doubtful that the mentioned kP calculations adequately describe the valence band at all dQW values.



Photoinduced Enhancement of the Excitonic Order in Strongly Correlated Electron Systems with the Spin Crossover
Abstract
A new mechanism of the photoinduced enhancement of the excitonic order in strongly correlated electron systems with the spin crossover through the generation of a massive mode in the spectrum of collective excitations is demonstrated.



Zavisimost' skorosti relaksatsii kogerentnykh sostoyaniy ot chisla Dependence of the Relaxation Rate of Coherent States on the Number of Correlated Spins and the Order of Coherence
Abstract
The relaxation of the components of the multiple-quantum NMR spectrum of a solid under the effect of the dipole–dipole interactions during the evolution period is considered. It is taken into account that clusters of dynamically correlated spins of different sizes are formed in the preparatory period, and their degradation depends on their size and coherence order. To calculate the size distribution function of clusters and their degradation function, a physical model including relaxation processes is developed. Using this model, an analytical result for a multiple-quantum spectrum is obtained. Agreement is obtained between the theoretical and experimental dependences of the coherence degradation rates in adamantane scaled by the square root of the average cluster size. The parameters of the above functions are found from the comparison of these dependences.



Giant Spatial Redistribution of Electrons in a Wide Quantum Well Induced by Quantizing Magnetic Field
Abstract
In samples of field-effect transistors based on GaAs/AlGaAs heterostructures with an electron system in a single 50-nm-wide GaAs quantum well, a transition stimulated by a quantizing magnetic field has been detected from a bilayer state of the system in zero magnetic field to a single-layer state when only the lowest Landau level is filled. In contrast to the results for the 60-nm-wide quantum well obtained in [S. I. Dorozhkin, A. A. Kapustin, I. V. Fedorov, V. Umansky, and J. H. Smet, Phys. Rev. V 102, 235307 (2020)], the single-layer state is observed not only in incompressible quantum Hall effect states of the electron system at filling factors of 1 and 2, but also in compressible states between these filling factors. The spatial location of the single-layer system in the quantum well has been established; it appears to be independent of the electron distribution over the layers in a low magnetic field. A possible qualitative explanation for this observation has been proposed. The detected transition is supposedly due to the negative compressibility of two-dimensional electron systems caused by exchange-correlation contributions to the electron−electron interaction.



Memory Effects in the Nonequilibrium Critical Behavior of the Two-Dimensional XY Model in the Low-Temperature Berezinskii Phase
Abstract
The Monte Carlo study of nonequilibrium memory effects in the two-dimensional pure and structurally disordered XY model in the low-temperature Berezinskii phase has been performed. Features of the correlation between memory and aging effects have been demonstrated. A qualitatively novel phenomenon for memory effects has been revealed: dynamic curves of the autocorrelation function in the thermal cycling time interval tend to the dynamic curves with the initial temperature. A unique implementation of memory effects has been demonstrated at both cooling and heating cycling of the system under the condition that cooling and heating temperatures are in the low-temperature Berezinskii phase. The influence of structural disorder on memory effects has been analyzed. It has been found that they are enhanced in the structurally disordered system owing to the enhancement of aging effects.



Casimir–Lifshitz Friction Force and Kinetics of Radiative Heat Transfer between Metal Plates in Relative Motion
Abstract
The Casimir–Lifshitz friction force and the heating rates of two metal plates with a narrow vacuum gap between them during nonrelativistic motion of one of them are calculated within the framework of fluctuation electrodynamics taking into account the temperature change in material properties. It is shown that identical plates with the same initial temperature have the same heating rate, determined by the power of the friction force, and the possibility of measuring the friction force from the heating kinetics of nonmagnetic metal plates with temperatures of 1–10 K is substantiated.


