


Vol 117, No 9-10 (5) (2023)
Articles
Formation of a High-Energy Particle Beam by Means of Focusing Crystal Devices
Abstract
It becomes difficult and expensive to control TeV-particle trajectories using electromagnets to obtain extracted beams at accelerators. For these purposes, high-gradient devices based on bent crystals are more suitable. These crystals can serve as superstrong lenses with a focal length of less than 1 m with an equivalent magnetic field of 1000 T. In this work, a scheme based on two successive focusing crystals has been implemented to form a 50 GeV axially symmetric beam with a small divergence of 30 μrad in both the horizontal and vertical planes. One of the promising applications of this scheme is the creation of high-energy neutrino beams.



Lattice Study of the Equation of State of a Rotating Gluon Plasma
Abstract
The effect of uniform rotation on the equation of state of gluodynamics has been studied in lattice simulation. To this end, the system has been considered in the corotating reference frame, where the rotation can be modeled as an external gravitational field. The free energy of the studied system in the case of sufficiently slow rotation can be expanded in a power series in the angular velocity. The moment of inertia given by the second-order coefficient of this expansion has been calculated and its dependence on the temperature and the dimensions of the rotating system has been determined. Our results indicate that the moment of inertia of gluodynamics is negative up to the temperature T * ~ 1.5Tc, where Tc is the critical temperature of the confinement/deconfinement phase transition, and becomes positive at temperatures T > T *. The negative moment of inertia has been attributed to the thermodynamic instability of the gluon plasma with respect to uniform rotation.



Muon Puzzle in Ultra-High Energy EASs According to Yakutsk Array and Auger Experiment Data
Abstract
The lateral distribution of particles in extensive air showers from cosmic rays with energy above 1017 eV registered at the Yakutsk complex array was analyzed. Experimentally measured particle densities were compared to the predictions obtained within frameworks of three ultra-high energy hadron interaction models. The cosmic ray mass composition estimated from the readings of surface-based and underground detectors of the array is consistent with estimations obtained from measurements of lateral distribution of the air showers Cherenkov light emission. A comparison was made with the results of direct measurement of the muon component performed at the Pierre Auger Observatory. It is demonstrated that the densities of muon flux measured at Yakutsk array are consistent with results of fluorescent light measurements and disagree with results on muons obtained at the Auger array.



On the Possibility of Converting Linearly Polarized Attosecond Pulses of High Harmonics into Circularly Polarized Pulses with an Increase in the Energy in an Optically Modulated Neon-Like Active Medium of an X-Ray Plasma Laser
Abstract
A method is proposed for converting linearly polarized radiation of a single harmonic or a combination of high-order harmonics of an optical field, which form a train of subfemto-/attosecond pulses, into elliptically and, in particular, circularly polarized radiation in an optically modulated neon-like active medium of an X‑ray plasma laser. It is shown that this method can provide a high energy efficiency of radiation conversion due to the amplification of the harmonic field, and is also insensitive to changes in the number of high harmonics that form the amplified pulses. The possibility of experimental implementation of the method is considered on the example of an active plasma of neon-like Ti12+ ions with an unperturbed inverted transition wavelength of 32.6 nm.



Optomechanical Heating and Cooling via Tip-Enhanced Raman Scattering in Epsilon-Near-Zero Medium
Abstract
Media with the dielectric permittivity
close to zero (epsilon-near-zero or ENZ) maintain conditions for enhanced light-matter interactions. In this paper, we propose to use these media to enhance the optomechanical coupling of vibrational excitations of the medium with the optical near-field of the nanoantenna. It is shown that the ENZ medium significantly increases the optically induced decay rate of a vibration, which can be used for cooling (when the incident light frequency is less than the ENZ frequency) or heating (when the incident light frequency is greater than the ENZ frequency). Due to the proximity of the refractive index to zero as well, oscillations of the polarization of the medium are coherent, which further enhances the optomechanical effects. Analytical expressions are obtained for the optical shift of the resonance and the induced decay rate.



Stability of Solid Atomic Nitrogen Phases at Atmospheric Pressure
Abstract
Stability to the formation of vacancies in the bulk of a structure and the possibility of a stable surface have been examined for the first time with density functional theory for high energy density solid atomic nitrogen phases, whose dynamical stability at normal pressure is theoretically predicted. It has been shown that phases with of the
and Pccn crystal symmetries are unstable to the formation of vacancies at atmospheric pressure. The
and P21 phases are stable with respect to the formation of vacancies, but the surface of such structures introduces instability inducing their transition from a metastable atomic solid phase to a molecular one. The gauche phase of nitrogen with the I213 crystal symmetry is stable with respect to the considered structural perturbations and is the most promising for experimental synthesis at atmospheric pressure.



Dynamic Susceptibility of Skyrmion Crystal
Abstract
Using stereographic projection approach, we develop a theory for calculation of dynamic susceptibility tensor of Skyrmion crystals (SkX), formed in thin ferromagnetic films with Dzyaloshinskii–Moriya interaction and in the external magnetic field. Staying whenever possible within analytical framework, we employ the model ansatz for static SkX configuration and discuss small fluctuations around it. The obtained formulas are numerically analyzed in the important case of uniform susceptibility, accessible in magnetic resonance experiments. We show that, in addition to three characteristic magnetic resonance frequencies discussed earlier both theoretically and experimentally, one should also expect several resonances of smaller amplitude at somewhat higher frequencies.



Spin–Orbit Interaction in ZnO/MgxZn1 – xO Heterojunctions Probed by Electron Spin Resonance Spectroscopy
Abstract
The spin–orbit interaction in a series of ZnO/MgxZn1 – xO heterojunctions containing a two-dimensional electron system with a wurtzite structure has been studied in detail. The spin–orbit coupling constants have been determined from the analysis of the modification of the single-particle g-factor caused by the spin–orbit interaction in the quantum Hall effect regime. The g-factor has been measured with high accuracy by the electron paramagnetic resonance technique in wide ranges of magnetic fields and electromagnetic frequencies. The spin–orbit coupling constants have been determined for a series of samples with different Mg concentrations, which has allowed us to obtain the dependence of the spin–orbit coupling constant on the two-dimensional electron density n. The measured spin–orbit coupling constant is in the range of 0.5–0.8 meV Å and quite weakly depends on n. The coefficients specifying the linear and cubic contributions to the spin–orbit interaction determined from the approximation of the experimental data are α0 = 0.48 meV Å and γ = 0.12 eV Å3, respectively. These values are correlated with results obtained by other research groups.



Insight to structural, electronic, optical and thermoelectric propertiesof NaCaSb and KCaSb half Heusler compounds: a DFT approach
Abstract
Full-potential, linearized augmented plane wave approach (FP LAPW), as employed in Wien2K code was utilized to analyze structural, elastic, optoelectronic, and transport features of NaCaSb and KCaSb half–Heusler (HH) compounds. Generalized gradient approximation (GGA) was considered for structural optimization. The predicted lattice constants are in line with the prior theoretical and experimental findings. The examined NaCaSb and KCaSb compounds are inherently ductile and mechanically stable. The investigated HHs are semiconductors with a band gap 1.27 and 1.23 eV for NaCaSb and KCaSb, respectively, in the modified Becke–Johnson (mBJ) approximation. Calculated optical characteristics of NaCaSb and KCaSb point to their potential applicability in optoelectronic devices. Thermoelectric features were analyzed employing the Boltzmann transport provided in the BoltzTraP software. At room temperature, the significant figure of merit (ZT) values indicates that the investigated NaCaSb and KCaSb can be used for fabricating thermoelectric devices with the highest possible efficiency.



Detection of Electron Paramagnetic Resonance Spectra of Optically Induced Carriers with the Properties of the Effective Mass in the WS2 Transition Metal Dichalcogenide
Abstract
The spin properties of transition metal dichalcogenides are of interest for applications in spintronics. Anisotropic electron paramagnetic resonance spectra in a WS2 single crystal under optical excitation have been detected. These spectra assumingly belong to localized carriers near the valence band and reflect features of the 5d shell of the crystal. It has been shown that the g-factor for the magnetic field perpendicular to the c‑axis of the crystal (in-plane magnetic field) is larger than that for the magnetic field parallel to the c‑axis (perpendicular to the layer plane), which can provide information on the type of the 5d function. The discussed center is most likely described by the wavefunction, which can be associated with the valence band of the crystal.



Excitonic Order in Strongly Correlated Systems with the Spin Crossover
Abstract
Features of the formation of the magnetic structure and the exciton Bose–Einstein condensate phase of magnetic excitons in strongly correlated systems near the spin crossover have been considered with the effective Hamiltonian obtained from the two-band Hubbard–Kanamori model. The coexistence of antiferromagnetism and exciton condensate, as well as the appearance of the long-range excitonic antiferromagnetic order even in the absence of the interatomic exchange interaction, has been revealed. The role of the electron–phonon coupling has been considered.



Runge–Lenz Operator in the Momentum Space
Abstract
The fundamental quantum Coulomb problem in the momentum space is considered. A differential equation with SO(4) symmetry has been obtained in the momentum space instead of the integral Fock equation. The corresponding equation in the coordinate space is the sum of the squares of the angular momentum and Runge–Lenz operators. This approach is unknown in the momentum space where the Runge–Lenz operator is not applied. The Runge–Lenz operator obtained in the momentum space is simpler than that in the coordinate space and allows one to effectively consider the Coulomb problem in the momentum space. A relation of new operator to the infinitesimal rotation operator of the three-dimensional Fock sphere has been determined.






Interaction Potential of Protons and Hydrogen Atoms with Metals
Abstract
Approximate potentials for protons and hydrogen atoms in metals have been proposed. It has been shown that the difference between the interatomic interaction potentials obtained in the density functional theory for the gas phase and our potentials obtained by processing experimental data on the scattering of atomic particles from the surface of solids can be explained by including the screening of the charge of an incident particle. The effect of screening in the potential on the angular distributions of atomic particles passed through thin films and on nuclear stopping powers has been established.



Diffraction-Limited Focusing of Acoustic Waves by a Mesoscopic Flat Janus Lens
Abstract
Anisotropic focusing by a mesoscopic (Mie size parameter of about 18) acoustic cubic lens based on V-shaped plate structures has been simulated numerically and confirmed experimentally. It has been shown for the first time that this lens with an edge dimension of about three wavelengths ensures the focusing of an acoustic wave in air into a diffraction-limited region. In the inverse geometry of the structure, the lens completely reflects the incident acoustic wave.



Increase in the Efficiency of the Isotope-Selective Infrared Laser Multiphoton Dissociation of 11BCl3 Molecules in a Mixture with SF6 Serving As a Sensitizer and an Acceptor of Radicals
Abstract
A strong increase in the efficiency of the isotope-selective infrared laser multiphoton dissociation of 11BCl3 molecules in the natural mixture with 10BCl3 by radiation of a pulsed CO2 laser in the case of admixture of SF6 molecules, which serve as a sensitizer and simultaneously acceptors of radicals, Cl atoms formed in the dissociation of BCl3 molecules, has been detected. The yield and selectivity of dissociation of 11BCl3 molecules increase by several times and the threshold energy density for the dissociation of molecules decreases significantly in the case of their irradiation in the mixture with SF6 compared to irradiation without SF6. This property allows the single-frequency isotope-selective dissociation of 11BCl3 molecules by unfocused laser radiation at a moderate energy density (≈3–5 J/cm2), which is important and relevant for the practical implementation of the laser separation of boron isotopes.



Quasicrystalline Structures with Narrow-Band Frequency–Angular Selectivity
Abstract
Design methods in the reciprocal space allow one to obtain structures with desired properties. Quasicrystalline photonic structures, which ensure the selective scattering of an electromagnetic wave incident on the sample, have been designed. The maxima of the Fourier transform of the desired distribution of the permittivity in the reciprocal space are located along two arcs on the Ewald sphere, which corresponds to the scattering of the wave with the required wavelength and angle of incidence. The material distribution has been determined by the transition to the real space. A structure with a low dielectric contrast has been formed after the binarization of the refractive index. The theoretical analysis of the properties of the structure has confirmed the frequency–angular selectivity of scattering. The numerical calculations show the possibility of achieving the effective scattering and absorption of the electromagnetic energy up to 94% in a narrow frequency range and in a narrow interval of angles of incidence at a dielectric contrast of two materials of 1.07.



Characteristics of “Dust” Fluxes from the Surface of Copper and Lead Liners Exposed to One or Two Successive Shock Waves
Abstract
Comparative experimental studies of the shock-induced particle ejection (“dusting”) from the free rough (Rz20) surface of copper and lead liners exposed to one or two successive shock waves separated in time by 0.2 μs have been carried out for the first time. This situation usually occurs in cumulative systems for the compression of the plasma by cylindrical or spherical liners shock or quasi-isentropically accelerated by explosion products. Using pulsed X-ray diffraction, laser optical recording, piezoelectric pressure sensors, and heterodyne interferometry, a qualitative picture has been studied and the quantitative characteristics of particle ejection from the free surface such as the velocities of the free surface and the particle flux front and the density (mass) distribution of particle flux in the direction of its motion, which are necessary for more accurate determination of features and the development of more appropriate models of the effect, have been evaluated.



Formation of Droplets of the Order Parameter and Superconductivity in Inhomogeneous Fermi–Bose Mixtures (Brief Review)
Abstract
The studies of a number of systems treated in terms of an inhomogeneous (spatially separated) Fermi–Bose mixture with superconducting clusters or droplets of the order parameter in a host medium with unpaired normal states are reviewed. A spatially separated Fermi–Bose mixture is relevant to superconducting Ba-KBiO3 bismuth oxides. Droplets of the order parameter can occur in thin films of a dirty metal, described in the framework of the strongly attractive two-dimensional Hubbard model at a low electron density with a clearly pronounced diagonal disorder. The Bose–Einstein condensate droplets are formed in mixtures and dipole gases with an imbalance in the densities of the Fermi and Bose components. The Bose–Einstein condensate clusters also arise at the center or at the periphery of a magnetic trap involving spin-polarized Fermi gases. Exciton and plasmon collapsing droplets can emerge in the presence of the exciton–exciton or plasmon–plasmon interaction. The plasmon contribution to the charge screening in MgB2 leads to the formation of spatially modulated inhomogeneous structures. In metallic hydrogen and metal hydrides, droplets can be formed in shock-wave experiments at the boundary of the first-order phase transition between the metallic and molecular phases. In a spatially separated Fermi–Bose mixture arising in an Aharonov–Bohm interference ring with a superconducting bridge in a topologically nontrivial state, additional Fano resonances may appear and collapse due to the presence of edge Majorana modes in the system.



Svyaz' mezhdu magnitnymi i elektricheskimi svoystvami v serii nanochastits CoxZn1−xFe2O4
Abstract



Influence of the Magnetic Domain Structure on Polarization Effects in the Mössbauer Spectra of Iron Borate FeBO3 Single Crystals
Abstract
The Mössbauer spectra of FeBO3 single crystals are studied at temperatures above and below the magnetic transition point at different orientations of the crystals with respect to the propagation direction of γ rays. To describe the Mössbauer spectra, a theoretical model is developed with allowance for different orientations of magnetic moments in the crystal plane. It is found that the magnetic domain structure in iron borate significantly affects the shape of the Mössbauer spectra and the intensity of resonant transitions. The proposed model may be useful for determining the configuration of the magnetic domain structure of materials from Mössbauer spectroscopy data.



Tilt and Anisotropy of the Dirac Spectrum Caused by the Overlapping of Bloch Functions
Abstract
It has been shown that the overlapping of bands belonging to equivalent representation of the symmetry group is possible in systems with Dirac points appearing at the crossing of these bands. This overlapping results in the tilt and additional anisotropy of the Dirac spectrum, as well as in the renormalization of the velocity. At the same time, overlapping does not violate the general conditions of existence of the stable band crossing point. The effective Dirac Hamiltonian in the presence of band overlapping is pseudo-Hermitian and corresponds to the effective action of a massless spinor field in the curved spacetime.



Density Functional Theory, Molecular Dynamics, and AlteQ Studies of Baimantuoluoamide A and Baimantuoluoamide B to Identify Potential Inhibitors of Mpro Proteins: a Novel Target for the Treatment of SARS COVID-19
Abstract
COVID-19 has resulted in epidemic conditions over the world. Despite efforts by scientists from all over the world to develop an effective vaccine against this virus, there is presently no recognized cure for COVID-19. The most succeed treatments for various ailments come from natural components found in medicinal plants, which are also crucial for the development of new medications. This study intends to understand the role of the baimantuoluoamide A and baimantuoluoamide B molecules in the treatment of Covid19. Initially, density functional theory (DFT) used to explore their electronic potentials along with the Becke3–Lee–Yang–Parr (B3LYP) 6-311 +
basis set. A number of characteristics, including the energy gap, hardness, local softness, electronegativity, and electrophilicity, have also been calculated to discuss the reactivity of molecules. Using natural bond orbital, the title compound’s bioactive nature and stability were investigated. Further, both compounds potential inhibitors with main protease (Mpro) proteins, molecular dynamics simulations and AlteQ investigations also studied.



Emergent long-lived Zitterbewegung in Su–Schrieffer–Heeger lattice with third-nearest-neighbor hopping
Abstract
We investigate the wavepacket dynamics of quasiparticles in a Su–Schrieffer–Heeger lattice with third-nearest-neighbor hopping. The results reveal that the life-span of Zitterbewegung can be prolonged. To better understand the mechanism, we discuss the band structure and the long-time average of inverse participation rate. The results show that the band structure can be effectively manipulated as a quasi-flat band by introducing the third-nearest-neighbor hopping. This, as a unique advantage over the standard Su–Schrieffer–Heeger model, will bring about restrained diffusion of the wavepacket as well as dramatically stretched life-span of Zitterbewegung, thus will promise wide applications in condensed matter physics.


