bluuebunny/crossref_metadata_2025 huggingface dataset:
Hexagonal Diamond: Theoretical Study of Methods of Fabrication and Experimental Identification
Authors: Greshnyakov V. A.
Published: April 2024

Methods for the formation of hexagonal (2H) diamond from diamond polytypes under various types of deformation of the structure have been studied using density functional theory in the generalized gradient approximation. It has been established that the most appropriate method for the formation the structure of the 2H diamond polytype is the application of shear stresses 102.9 GPa along the [211] direction to the (111) planes of cubic diamond when pressures along the [111], [110], and [211] axes reach 21.6, 21.7, and 69.9 GPa, respectively. Raman and X-ray absorption spectra have also been calculated for various diamond polytypes. The analysis of calculated spectra shows that hexagonal diamond can be unambiguously identified if other diamond polytypes with nonzero hexagonality are absent in the system under study. In addition, Raman spectroscopy data and characteristic electron energy losses have been analyzed in order to determine the presence of 2H diamond in artificial or natural carbon compounds. It has been established that hexagonal diamond in the pure form has not yet been obtained and the structure of synthesized compounds is close to the structure of polytypes with a long lattice period or with a random packing of layers.
A Compatible System of Equations Related to the Lie Superalgebra gl(n|m) and Integrable Calogero–Moser Model
Authors: Dotsenko E.
Published: April 2024

A joint system of equations based on the superalgebra has been determined and its relation to the integrable Calodgero–Moser system of particles has been established.
τ Lepton Decays with Production of Strange Scalar Mesons K∗(700) and K∗(1430) in the Extended Nambu–Jona-Lasinio Model
Authors: Volkov M. K , Nurlan K.
Published: April 2024

The branching fractions of τ lepton decays with the production of strange scalar mesons both in the ground and first radially excited states @ and @are calculated in the extended @ chiral quark Nambu–Jona-Lasinio model. All mesons are considered as @ systems. The obtained results should be considered as predictions for future experiments.
Decomposition of the Static Potential in SU(3) Gluodynamics
Authors: Bornyakov V. G , Kudrov I. E
Published: April 2024

After fixing the Maximal Abelian gauge in lattice gluodynamics we decompose the nonabelian gauge field into the Abelian field created by Abelian monopoles and the modified nonabelian field with monopoles removed. We then calculate respective static potentials in the fundamental representation and show that the sum of these potentials approximates the nonabelian static potential with good precision at all distances considered. Comparison with other ways of decomposition is made.
Backscattering of Infrared Radiation by a Model Multilayer Biological Tissue
Authors: Zhavoronkov Yu. A , Ul'yanov S. V , Val'kov A. Yu , Kuz'min V. L
Published: April 2024

The intensity of backscattering of near infrared laser radiation has been calculated for a multilayer biological tissue simulating the human head as a function of the distance between a source and a detector of radiation that are located on the head. The iterative solution of the Bethe–Salpeter equation has been represented as a series in scattering orders. A modification of the known Monte Carlo method for photon transport in multilayer tissues has been proposed to accelerate calculations. It has been shown that the resulting dependences of the backscattering intensity change significantly under the variation of the optical properties of the biological tissue, primarily in the case of penetration of blood to the cerebrospinal fluid layer. This can be used to develop optical methods for diagnosis of traumatic injuries of biological tissues.
Nonlinear Response of Diluted Gases to an Ultraviolet Femtosecond Pulse
Authors: Vrublevskaya N. R , Shipilo D. E , Nikolaeva I. A , Panov N. A , Kosareva O. G
Published: April 2024

Quantum-mechanical simulations of the nonlinear response of a one-dimensional quantum system with the energy structure close to that of the xenon atom to an ultraviolet femtosecond pulse with an intensity of 1–100 TW/cm2 reveal the dispersion of the cubic nonlinearity coefficient in the range of 266–400 nm and its intensity dependence. This excludes the description of the response of bound electrons as. The calculation of the polarization with this one-dimensional quantum model can be used to simulate the propagation of ultraviolet femtosecond radiation in a gas.
Interaction of Heavy Ion Beams with Plasma Electrons: Role of Many-Electron Ionization Processes
Authors: Andreev G. I , Bychkov V. L , Shevel'ko V. P
Published: April 2024

Processes of multiple electron-impact ionization of ions in a plasma and a beam passing through the plasma have been considered. Using experimental data and theoretical calculations of the cross sections for n-electron ionization, the contribution from many-electron ionization ratesto the total ionization rate has been determined as a function of the electron temperature of the plasma T. It has been shown that the total contribution of many-electron ionization rates to the total ionization rate in ion beams passing through the plasma is determined by the relation between the velocity of an ion beamand the thermal velocity of electrons in the plasma. Many-electron ionization rateshave been numerically calculated for W+ ions for electron temperatures of the plasma from 1 eV to 10 keV and velocities of the ion beam= 0–30 a.u., where 1 a.u. ≈ 2.2 × 108 cm/s is the atomic unit of velocity.
Bonding Duality and Optoelectronic Properties of Bilayer Carbon Structures Based on the T12 Phase and Penta-Graphene
Authors: Toksumakov A. N , Baydyshev V. S , Kvashnin D. G , Popov Z. I
Published: April 2024

Bilayer compounds of two-dimensional T12 phase carbon allotrope and penta-graphene have been studied using the electron density functional theory. The stability of the considered two-dimensional structures with different types of stacking order at different temperatures has been estimated from the calculated phonon spectra and molecular dynamics simulation. The stability of the two-dimensional planar structure up to 1350 K has been demonstrated. It has been shown that bilayer penta-graphene compounds with the AA' and AB' stacking orders have energy minima both in the state with the van der Waals interaction and in the form of covalently bonded layers in the AA-T12 and T12 phases. The barrier for the transition between covalently and van der Waals bonded AA' and AB' stacking orders has been analyzed. The calculated electronic and optical characteristics show that the band gap in the case of covalent bonding is much narrower than that in the case of van der Waals bonding.
Transfer of Secret Keys in a Quantum Network with Trusted Intermediate Nodes and with Block Cipher Encryption
Authors: Molotkov S. N
Published: April 2024

The quantum cryptography technology allows key distribution in individual segments of a network in a point–point configuration; then, keys in individual segments are used to protect traffic between any nodes of the network, which are not connected directly by a quantum channel. Correspondingly, the problem of negotiation (distribution) of keys between separate segments of the network appears. In this work, the problem of the transmission of an independent key through trusted nodes of the quantum network, between which keys are provided as a result of quantum key distribution, is considered. Quantum keys are used to encrypt the transmitted key. The transmitted key can be encrypted by both the block cipher and the one-time pad. It has been shown that the complexity of search for the key transmitted through the network depends on the imperfection of the external key and quantum keys as well as on the imperfection of the block cipher, i.e., on the average probability of collisions in the block cipher. The complexity in the case of the encryption of the transmitted key by the one-time pad depends only on the imperfection of the transmitted key and encryption keys. Perfect keys keep the perfectness of the transmitted key. In the block cipher, the transmitted key is no longer perfect even with the perfect keys in the measure of difference of the block cipher from the one-time pad. It has also been shown that the larger the number of collisions of the block cipher, i.e., the smaller the number of ciphertexts covered by the block cipher, the smaller the number of search steps required to find the key.
Form Factor in Transition Radiation from Hollow Beams
Authors: Sergeeva D. Yu , Tishchenko A. A
Published: April 2024

The form factor of a hollow electron beam for transition radiation has been calculated. It has been shown that the characteristics of coherent radiation are significantly different for conventional solid and hollow beams. Numerical estimates have been obtained for terahertz radiation frequencies and relativistic energies of el-ectrons.
Measurement of the Cross Section for the Neutron-Induced Fission of 238U Nuclei in the Energy Range of 0.3–500 MeV
Authors: Vorob'ev A. S , Gagarskiy A. M , Shcherbakov O. A , Vayshnene L. A , Barabanov A. L
Published: April 2024

The cross section for the neutron-induced fission of 238U nuclei has been measured using the time-of-flight spectrometer of the GNEIS neutron complex at the Petersburg Nuclear Physics Institute, National Research Center Kurchatov Institute, in the neutron energy range of 0.3–500 MeV. Fission fragments have been detected by low-pressure position-sensitive multiwire proportional counters. The cross section for 238U(n, f) fission has been measured with respect to the cross section for 235U(n,  f) fission, which is an accepted international standard. Data on the energy dependence of the anisotropy of the angular distribution of fragments of neutron-induced 238U nuclei are also presented. The data obtained have been compared to previous experiments carried out using both similar and significantly different methods.
Polarization Switching of a Rochelle Salt Single Crystal in a Magnetic Field
Authors: Yakushkin E. D
Published: April 2024

A change in the parameters of electrical switching in an applied magnetic field has been found in a Rochelle salt single crystal. The modified hysteresis loop in the case of switchable polarization implies a deceleration in the motion of ferroelastic domains. The effect is apparently related to the magnetically stimulated enhancement of the domain wall pinning.
Magnetic anisotropy of single-ion magnet (PPh4)2[ReF6] · 2H2O
Authors: Taran L. S , Elfimova V. Y , Streltsov S. V
Published: April 2024

Studying of single-molecule magnets has sprung many surprises such as, e.g., quantum tunneling of the magnetization, which is strongly related to the presence of a magnetic anisotropy. Electron spin resonance and inelastic neutron scattering measurements of (PPh4)2[ReF6]⋅2H2O complex evidence an unprecedented large single-site magnetic anisotropy of D@35 K in this material. Using state-of-the-art ab initio calculations we found that the single-ion anisotropy is indeed very large (but does not exceed 12 K) and revealed the physical mechanism lying behind this phenomenon.
Lattice Study of the Equation of State of a Rotating Gluon Plasma
Authors: Braguta V. V , Kudrov I. E , Roenko A. A , Sychev D. A , Chernodub M. N
Published: April 2024

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.
Tilt and Anisotropy of the Dirac Spectrum Caused by the Overlapping of Bloch Functions
Authors: Alisultanov Z. Z , Demirov N. A
Published: April 2024

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.
Towards
-Symmetric Optical Dimer Fabrication without a Light-Absorbing Material
Authors: Dmitriev A. A , Baryshnikova K. V , Rybin M. V
Published: April 2024

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.
Inverse Faraday Effect in Superconductors with a Finite Gap in the Excitation Spectrum
Authors: Putilov A. V , Mironov S. V , Mel'nikov A. S , Bespalov A. A
Published: April 2024

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.
Energy Spectrum of β Electrons in Neutrinoless Double-β Decay Including the Excitation of the Electron Shell of Atoms
Authors: Krivoruchenko M. I , Tyrin K. S , Karpeshin F. F
Published: April 2024

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 germaniumhave 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.
Natural Explanation of Recent Results on e+e- → λλ¯
Authors: Mil'shteyn A. I , Sal'nikov S. G
Published: April 2024

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.
Sharp Focusing of an Atomic Beam with the Doppler and Sub-Doppler Laser Cooling Mechanisms in a Two-Dimensional Magneto-Optical Trap
Authors: Bykova D. V. , Afanas'ev A. E. , Balykin V. I.
Published: April 2024

The focusing of an atomic beam with the use of a two-dimensional magneto-optical trap in order to increase the number of atoms in the region of their laser cooling and localization near an atom chip is discussed. Two regimes of the interaction of atoms with a focusing laser field are considered: (i) the Doppler interaction regime, which occurs at small detunings of the laser field from the atomic resonance, and (ii) the sub-Doppler interaction regime, which occurs at large detunings of the laser field from the atomic resonance. The efficiency of focusing in the first case is low because of the momentum diffusion. It has been shown that the momentum diffusion in the sub-Doppler cooling mechanism is insignificant and, as a result, the broadening of the transverse velocity distribution of atoms is small. The sharp focusing of the atomic beam is possible in this interaction regime.
Weak Localization of Light in a Magneto-Active Medium
Authors: Gorodnichev E. E. , Rogozkin D. B.
Published: April 2024

The interference contribution to the optical conductance (total transmittance) of a sample of a disordered Faraday medium is calculated. The suppression of wave interference in a magnetic field is shown to be due to helicity-flip scattering events. The magnetic field does not destroy the interference of waves with a given helicity, but suppresses it if the helicity changes along different parts of the wave trajectory. This leads to a decrease in the interference contribution to the conductance with increasing the magnetic field. A similar phenomenon, negative magnetoresistance, is known as a consequence of weak localization of electrons in metals with impurities. It is found that, as the magnetic field increases, the change in the interference correction to the optical conductance tends to a certain limiting value, which depends on the ratio of the transport mean free path to the helicity-flip scattering mean free path. We also discuss the possibility of controlling the transition to the regime of strong “Anderson” localization in the quasi-one-dimensional case by means of the field.
Evolution of the Electronic Properties of SrFe1 − x − y − zAlxMnyCozO3 Solid Solutions Depending on the Composition and the Degree of Localization of Electronic States
Authors: Zaynullina V. M. , Korotin M. A. , Kozhevnikov V. L.
Published: April 2024

The genesis of the electronic spectrum in SrFe1 −xAlxO3, SrFe1 −xMnxO3, SrFe1 −xCoxO3, SrFe1 − 2xAlxCoxO3, and SrFe1−y−zMnyCozO3cubic solid solutions of strontium ferrite, where0⩽x⩽0.15and0⩽y,z⩽0.125, is studied in the coherent potential approximation. The inclusion of electron correlations on 3datoms makes it possible to reproduce the experimental content tendencies in the variation of the electronic and magnetic properties. It is shown that codoping of ferrite with cobalt and aluminum effectively increases the concentration of electron carriers and their degree of localization in SrFe1 −x− 0.15AlxCo0.15O3, which is of interest in the development of oxide thermoelectrics. Due to a relatively large contribution from delocalized states at the Fermi level, SrFe1 −y−zMnyCozO3solid solutions withy=z=0.1−0.12are promising electrode materials.
Anomalous Behavior of the Tunneling Magnetoresistance in (CoFeB)x(LiNbO3)100 − x/Si Nanocomposite Film Structures Below the Percolation Threshold: Manifestations of the Cotunneling and Exchange Effects
Authors: Nikolaev S. N. , Chernoglazov K. Yu. , Emel'yanov A. V. , Sitnikov A. V. , Taldenkov A. N. , Patsaev T. D. , Vasil'ev A. L. , Gan'shina E. A. , Demin V. A.
Published: April 2024

A strongly nonmonotonic temperature dependence of the magnetoresistance in (CoFeB)x(LiNbOy)100 –xfilm nanocomposites (x≈ 40–48 at %) is observed in the temperature range of 3–250 K at the magnetic field up to 14 T near the percolation threshold on its insulating side. The magnetoresistance has a minimum at 40K and increases steeply on cooling. Such behavior of the magnetoresistance is attributed to the coexistence of superferromagnetic regions with exchange-coupled granules separated by regions with superparamagnetic granules in the nanocomposite. In this case, an increase in the negative magnetoresistance atT 40 K is due to the destruction of superferromagnetic ordering, whereas an increase in the magnetoresistance atT 40 K is related to the processes involving simultaneous elastic tunneling via the chains of granules. At the saturation of the magnetization, an additional negative contribution arises, which is probably due to the quantum interference effects. AtT 4 K, a double-well shape of the field dependence of the magnetoresistance is observed, which could be attributed to the effect of a positive contribution that competes with the negative magnetoresistance.
Effect of Quantum Decoherence on Collective Neutrino Oscillations
Authors: Purtova A. A. , Stankevich K. L. , Studenikin A. I.
Published: April 2024

The effect of the quantum decoherence of neutrino mass states on collective oscillations of neutrinos has been studied for the case of three flavors using a method based on the stability analysis of the Lindblad equation with the neutrino evolution Hamiltonian including the effects of the self-interaction. New analytical conditions for the appearance of collective neutrino oscillations in supernova explosions have been obtained taking into account the quantum decoherence of neutrinos.
Calculations of the Binding-Energy Differences for Highly-Charged Ho and Dy Ions
Authors: Savel'ev I. M. , Kaygorodov M. Yu. , Kozhedub Yu. S. , Tupitsyn I. I. , Shabaev V. M.
Published: April 2024

The binding-energy differences for163Hoq+and163Dyq+ions with ionization degreesq=38, 39, and 40 are calculated. The calculations are performed using the large-scale relativistic configuration-interaction and relativistic coupled-clusters methods. The contributions from quantum-electrodynamics, nuclear-recoil, and frequency-dependent Breit-interaction effects are taken into account. The final uncertainty does not exceed 1 eV. Combining the obtained results with the binding-energy difference for neutral atoms calculated in [I.M.Savelyev, M.Y. Kaygorodov, Y.S. Kozhedub, I.I. Tupitsyn, and V.M. Shabaev, Phys. Rev. A105, 012806 (2022)], we get the secondary differences of the ion–atom binding energies. These values can be used to evaluate the amount of energy released in the electron capture process in163Hoatom (theQvalue), provided mass differences of highly charged ions163Hoq+and163Dyq+is known from experiment. TheQvalue is required by experiments on the determination of the absolute scale of the electron neutrino mass by studying the beta-decay process.
Detection of Radiation Generated by Moving Josephson Vortices in a Bi2 + xSr2 – xCuO6 + δ Single Crystal in High Magnetic Fields Directly in the Sample
Authors: Vedeneev S. I.
Published: April 2024

A high-temperature superconductor sample with numerous internal Josephson junctions formed by atomic layers is a nonlinear system with unique dynamic properties. An external magnetic field penetrates in the sample in the form of moving Josephson vortices, which generate radiation. It has been shown that this radiation in a Bi2 +xSr2 –xCuO6 + δ(Bi2201) single crystal can be detected by means of a Josephson junction on a microbreak (break junction) directly inside the single crystal.
Resonances for a Solvable Model of Ultrasound Scattering by a Cell Membrane
Authors: Popov I. Yu. , Yurova T. S.
Published: April 2024

We study the resonances for scattering of acoustic waves by cell membrane. Due to the fact that we deal with this phenomenon only, we use the simplest model of the membrane as a potential supported by a surface. The asymptotics of the Green’s function with the singularity at the surface is obtained. The influence of the surface curvature on the resonances is investigated. An application of the result to explanation of selective cancer cell membrane destruction in ultrasonic field is discussed.
Search for 8.4-keV Solar Axions Emitted in the M1 Transition in 169Tm Nuclei
Authors: Derbin A. V. , Drachnev I. S. , Muratova V. N. , Semenov D. A. , Trushin M. V. , Unzhakov E. V.
Published: April 2024

Axions with an energy of 8.4 keV emitted in theМ1 transition in169Tm nuclei in the Sun are sought in theA+169Tm→169Tm* →169Tm+(γ,e)(8.4 keV) reaction of resonant absorption by169Tm nuclei on the Earth using aTm3Al5O12thulium garnet crystal as a bolometric detector. The flux of monochromatic 8.4‑keV axions has been calculated. New constraints on the axion–nucleon coupling constants have been obtained and, as a result, new upper bounds on the axion massmAKSVZ⩽141eV andmADFSZ⩽244eV have been obtained at 90% C.L. in the KSVZ and DFSZ models, respectively.
Effect of Meteorological Parameters on the Cosmic Muon Flux Studied Using the Effective Generation Level Method with the DANSS Detector Data
Authors: Alekseev I. G. , Belov V. V. , Danilov M. V. , Zhitnikov I. V. , Zinatulina D. R. , Kazartsev S. V. , Kobyakin A. S. , Kuznetsov A. S. , Machikhil'yan I. V.
Published: April 2024

The DANSS detector is located directly under the nuclear reactor at the Kalinin nuclear power plant. Such a position ensures about 50 m.w.e. shielding from cosmic rays in the vertical direction; as a result, the detector occupies an intermediate position between surface and underground detectors in the shielding from cosmic rays. The sensitive volume of the detector consisting of a 1-m3plastic scintillator is surrounded by the multilayer passive shielding and muon veto. The main aim of the DANSS experiment is to measure the antineutrino spectrum at various distances from the source. To this end, the detector is placed on a lifting platform in order to record data at three positions of 10.9, 11.9, and 12.9 m from the reactor core. The detector can reconstruct muon tracks passing through its sensitive volume. The pressure, temperature, and decay coefficients for muons in various regions of the zenith angleθhave been determined from the muon data collected during four years using the effective generation level method.
Neutral Bremsstrahlung Electroluminescence in Noble Liquids Revisited
Authors: Buzulutskov A. F. , Frolov E. A.
Published: April 2024

Recent discovery of neutral bremsstrahlung (NBrS) mechanism of electroluminescence (EL) in noble gases in two-phase detectors for dark matter searches has led to a prediction that NBrS EL should be present in noble liquids as well. A rigorous theory of NBrS EL in noble liquids was developed accordingly in the framework of Cohen–Leckner and Atrazhev formalism. It has been recently followed by the first experimental observation of NBrS EL in liquid argon, which however deviates significantly from the previous theory. Given these results, we revise previous theoretical calculations of EL NBrS in noble liquids to be consistent with experiment. In particular, NBrS EL yield and spectra were calculated in this work for argon, krypton, and xenon with momentum-transfer cross section for electron scattering (instead of energy-transfer one) being used for calculation of NBrS cross section. The results for light noble liquids, helium and neon, are also reexamined.
Rivulet of a Non-Newtonian Fluid Draining on an Inclined Superhydrophobic Surface
Authors: Ageev A. I. , Osiptsov A. N.
Published: April 2024

A rivulet of a power-law-rheology fluid steadily draining from a point source on an inclined superhydrophobic plane is considered. An equation for the shape of the cross section of the rivulet has been derived in the thin layer approximation with the inhomogeneous slip boundary condition (slip coefficients are power functions of the spatial coordinates). Under the assumption that the rivulet is symmetric with respect to its middle plane, the conditions for the existence of a class of self-similar solutions of one ordinary differential equation of the second order have been determined. For some slip parameters of the superhydrophobic surface and some rheological indices of the draining fluid, analytical and numerical solutions from the found class have been constructed and the shape of the cross section of the rivulet and the geometry of the wetting spot have been analyzed.
Unique Structural Features of NbS3 Ribbon Whiskers
Authors: Martovitskiy V. P. , Klokov A. Yu. , Pokrovskiy V. Ya.
Published: April 2024

The X-ray diffraction analysis of NbS3ribbon whiskers has revealed three structural features: (i) a fine-crystalline structure throughout the entire volume with the preferred orientation along the [001] direction perpendicular to the longbaxis of the whisker, (ii) the combination of crystalline macroblocks with a length up to 0.5 mm with small crystallites of various orientations, and (iii) the combination of crystalline macroblocks with the left-hand twisting of planes around thebaxis with a pitch angle of 1.25° per every 0.2 mm and with the return to the initial orientation in the next block. Structural features (ii) and (iii) of NbS3whiskers have not yet been observed, and inorganic crystals with such properties are absent to the best of our knowledge. All crystallites have a unit cell with almost right angles and approximately the same lattice constantc(18.130 Å), whereas the lattice constantsaandbare noticeably different in a single sample. All crystallites can be referred to phase IV rather than to phase I, as expected. The right angle between theaandcaxes can be explained by the twinning of phase I along thecaxis. Differences in the lattice constants in macroblocks indicate large stresses in structures. Such stresses near twins (and/or stacking faults) can significantly affect the free electron density and play a key role in the formation of charge density waves in various phases of NbS3.
Generation of Giant Magnetic Fields in a Hollow Mesoscale Sphere
Authors: Minin O. V. , Dzhou S. , Minin I. V.
Published: April 2024

The superresonance effect for a hollow dielectric sphere is numerically simulated with the Mie theory. It is shown for the first time that weakly dissipative mesoscale spheres with an air-filled cavity exhibit a high-order Fano resonance related to internal Mie modes. Superresonance in a hollow sphere is achieved by the accurate choice of the cavity radius, while for a monolithic dielectric sphere, it is ensured by the accurate choice of the outer diameter of the particle under study. In this case, the relative intensities of the resonance peaks in the optical range for both magnetic and electric fields near the sphere poles can have enormous values of 106−107, if the magnetic field magnitude exceeds that of the electric field by a factor larger than 15 for the hollow sphere with a Mie size parameter about 40.
Intrachain Distances in a Crumpled Polymer with Random Loops
Authors: Slavov B. , Polovnikov K.
Published: April 2024

Crumpled polymer further folded into random loops has been proposed as a minimal model of chromosome organization. How do loops affect spatial distances in such a polymer? Here we investigate the statistics of intrachain distances,R(s), at different length scalessin the ensemble of polymer configurations with frozen (quenched) disorder of loops. We delineate the effect of the loops by solving the model analytically for the crumpled polymer chain, which was long suggested as a null model of chromatin organization. As we show, the chain compacts across scales upon folding into loops and features a characteristic “toe” inR(s)at the length scale of several loop sizes λ. Quantitatively comparingR(s)with the behavior of the contact probability function,Pc(s), computed in our previous works K. Polovnikov and B. Slavov, Phys. Rev. E107, 054135 (2023) [1] and K. E. Polovnikov, B. Slavov, S. Belan, M. Imakaev, H. B. Brandáo, and L. A. Mirny, bioRxiv: 2022.02.01.478588 [2], we further demonstrate breaking of the famous mean-field relation between the two observables. The latter result is a striking manifestation of the non-Gaussianity of the polymer ensemble, induced by the loops disorder. Altogether, our theoretical findings pave the way towards quantitative inference of parameters of loopy chromosomes from the microscopy data in vivo and warn researchers against using Gaussian methods of analysis of population-averaged conformation capture datasets (e.g., Hi-C).
π0, η, η' → γγ Decays and the Explicit Chiral Symmetry Breaking
Authors: Osipov A. A.
Published: April 2024

Corrections to the Wess–Zumino–Witten anomaly caused by the explicit breaking of theSU(3)×SU(3)chiral symmetry are studied using the effective meson Lagrangian based on the Nambu–Jona-Lasinio model with the simultaneous expansion in derivatives, current quark masses, and 1/Ncpowers. The leading contribution and the first correction for the amplitudes of the π0, η, η' → γγ decays and the contact term in theη/η′→π+π−γamplitudes have been calculated. The results are compared with similar 1/Ncchiral perturbation calculations and existing experimental data.
Influence of Electron Confinement Effects on the Band Gap of Almost Monatomic EuS2 Layers
Authors: Ekimov E. A. , Nikolaev S. N. , Kondrin M. V. , Krivobok V. S.
Published: April 2024

Europium disulfide is a layered semiconductor with a quasi-ionic bond type. Previously, it has been demonstrated that almost monatomic films can be formed from this material by mechanical splitting. In this work, the most energetically favorable structure of monatomic films is established using ab initio calculations, and the behavior of the band gap depending on the number of monolayers in the film is studied. To establish the role of nonlocal corrections and corrections associated with the spin–orbit interaction, the calculation results are compared with the position of the direct fundamental absorption edge of bulk crystals estimated from the experimental hot photoluminescence and microreflection spectra. It is found that the indirect character of the band gap is also retained in thin films. The confinement effects (dimensional localization of electrons) cause inhomogeneous broadening of the band gap over the Brillouin zone. The gap width almost does not change between the bulk material and its films at the edges of the Brillouin zone, and a significant change occurs only in the center of the Brillouin zone. A singularity in the density of states caused by the equalization of the energies for the D and E0points of the Brillouin zone is predicted in EuS2films about 10 ML thick.
On the Electric Area of an Electromagnetic Pulse
Authors: Bogatskaya A. V. , Popov A. M.
Published: April 2024

The propagation of ultrashort electromagnetic pulses with a nonzero electric area in plasma media is analyzed. An equation for the area of an electromagnetic pulse in the one-dimensional geometry has been derived in the unidirectional propagation approximation. It has been shown that this area is not an invariant of motion and can both decrease and increase during the propagation of the pulse depending on the properties of a plasma medium.
Generation of Long-Wavelength Stimulated Emission in HgCdTe Quantum Wells with an Increased Auger Recombination Threshold
Authors: Mazhukina K. A. , Rumyantsev V. V. , Dubinov A. A. , Utochkin V. V. , Razova A. A. , Fadeev M. A. , Spirin K. E. , Zholudev M. S. , Mikhaylov N. N.
Published: April 2024

Various designs of dielectric waveguides made of heterostructures with CdHgTe quantum wells grown by molecular beam epitaxy have been studied to generate stimulated emission in the 15–30 μm wavelength range. The reduction of radiation losses in optimized structures has made it possible to reduce the threshold intensity of the generation of stimulated emission to ~100 W/cm2. Modernized growth technology has ensured the reduction of the residual cadmium content in HgCdTe quantum wells to 2.5%, which has allowed us to increase the threshold energy of Auger recombination, as well as the maximum temperature for the observation of stimulated emission at interband transitions above 100 K. The results obtained are prerequisites for the implementation of coherent radiation sources exceeding in characteristics of lead–tin chalcogenide lasers used in the 15–30 μm spectral range.
Effective Hamiltonian of Topologically Protected Qubit in a Helical Crystal
Authors: Niyazov R. A. , Aristov D. N. , Kachorovskiy V. Yu.
Published: April 2024

We study a superlattice formed by tunnel-coupled identical antidots periodically situated in a two-dimensional topological insulator placed in a magnetic field. The superlattice spectrum can be controlled by gate electrodes or by changing the magnetic flux through the antidots. We demonstrate that a topologically protected qubit appears at the boundary between two regions with different fluxes. The qubit properties depend on the value of the flux jump on the boundary and can be controlled by the gate voltage. We derive the effective Hamiltonian of such a qubit and analyze the dependence of its properties on the main parameters of the superlattice: the tunnel coupling between antidots, and the probability of jumps with the spin flip.
Estimates of Absolute Branching Fractions for the f0(1710) Decays and Radiative Transitions ψ(2S) → γf0(1710) and ϒ(1S) → γf0(1710)
Authors: Achasov N. N. , Shestakov G. N.
Published: April 2024

Using the result of the VES Collaboration forBr(J/ψ→γf0(1710)), we estimate the absolute branching fractions for thef0(1710)decays intoππ,KK¯,ηηand for the first time intoωωandωϕ. In addition, we estimate for the first timeBr(ψ(2S)→γf0(1710))≈ 3.5 × 10–5andBr(Υ(1S)→γf0(1710))≈ 1 × 10–5
Twin Bound States in the Continuum in a Waveguide Fabry–Pérot Resonator
Authors: Shubin N. M. , Kapaev V. V. , Gorbatsevich A. A.
Published: April 2024

We study bound states in the continuum (BICs) in a Fabry–Pérot (FP) resonator within a quantum-mechanical waveguide. We show that besides typical FP BICs corresponding to a discrete set of cavity lengths, there is a pair of symmetric and antisymmetric twin BICs (TBICs) if isolated mirrors possess BIC themselves. In contrast to the FP BIC, the TBIC does not require the formation of standing waves of the FP resonance between the mirrors. Therefore, the energy and parameters of TBICs are almost independent of the length of the FP resonator, and their wavefunctions have an exponentially small amplitude between the mirrors. Results of the numerical simulation of the 2D quantum-mechanical waveguide with attractive potentials (“impurities”) playing the role of mirrors of an FP resonator are supported by the illustrative analytical model.
Effect of the Energy Conservation Law, Space Dimension, and Problem Symmetry on the Poynting Vector Field Singularities
Authors: Tribel'skiy M. I.
Published: April 2024

A brief review is given of the author’s recent achievements in classifying singular points of the Poynting vector patterns in electromagnetic fields of complex configuration. The deep connection between the topological structure of the force lines pattern and the law of energy conservation, the symmetry of the problem, and the dimension of the space has been unveiled.
Nonlinear Optical Response of an Excited 1/3 Laughlin Liquid
Authors: Kulik L. V. , Zhuravlev A. S. , Larionov A. V. , Van'kov A. B. , Zagitova A. A. , Kukushkin I. V. , Umanskiy V.
Published: April 2024

An ensemble of neutral excitations in a 1/3 Laughlin liquid is studied experimentally. It has been found that excitations induce a nonlinear optical response in the form of a quadratic dependence of the reflection signal on the pump power. The reported experimental results have shown that the observed effect is due to the contribution of the coherent anti-Stokes–Stokes scattering from the excited Laughlin liquid.
Convolutional Neural Networks for Predicting Morphological and Nonlinear Optical Properties of Thin Films of Quasi-Two-Dimensional Materials
Authors: Popkova A. A. , Fedyanin A. A.
Published: April 2024

Two-dimensional materials are promising candidates for the creation of flat photonics devices. The main problem of using such materials for applied applications is the complexity of creating films of specified geometric parameters. The films of two-dimensional materials made by exfoliation or chemical deposition methods are usually randomly distributed over a large area and have a large thickness spread. In this paper, we use convolutional neural networks to predict the film thickness of a quasi-two-dimensional material based on optical microscopy data. Hexagonal boron nitride, which is actively used in the creation of flat electronic and optoelectronic devices, was chosen as a test material. Due to the high spatial resolution of microscopy, it is possible to achieve high accuracy in predicting the thicknesses of flat areas of the sample, which allows for rapid characterization of structures. In addition, using the example of the signal of the third optical harmonic, we show the possibility of predicting the magnitude of the nonlinear optical response of the film, which expands the scope of the method.
Comparison of the Gap Structure of Underdoped and Overdoped Superconducting Pnictides BaFe2 – xNixAs2
Authors: Kuz'micheva T. E. , Kuz'michev S. A. , Pervakov K. S. , Vlasenko V. A.
Published: April 2024

We compare the structure of the superconducting order parameter of overdoped BaFe1.88Ni0.12As2and underdoped BaFe1.92Ni0.08As2pnictides with similarTc≈18.0−18.3K. Using incoherent multiple Andreev reflection effect spectroscopy, we directly determined the magnitudes of the two microscopic superconducting order parameters: the small superconducting gap and probably anisotropic large gap, their characteristic ratios and temperature dependences. We discuss similarity and difference in the gap structure, as well as possible influence of antiferromagnetic phase to superconducting properties.
Influence of the Gd Concentration on Superconducting Properties in Second-Generation High-Temperature Superconducting Wires
Authors: Degtyarenko P. N. , Sadakov A. V. , Ovcharov A. V. , Degtyarenko A. Yu. , Gavrilkin S. Yu. , Sobolevskiy O. A. , Tsvetkov A. Yu. , Massalimov B. I.
Published: April 2024

Systematic studies of second-generation high-temperature superconducting wires with Gd excess relative to the stoichiometric GdBa2Cu3O7composition are reported. It has been revealed that filamentary defects in the form of non-superconducting Gd2CuO4phase located along the ab plane are formed during film growth. These inclusions lead to a change in the pinning mechanism of the vortex structure, due to which the peak of the critical current at +15% Gd is clearly observed.
Acoustic Coupling between Magnon Bose−Einstein Condensates in Yttrium Iron Garnet Films
Authors: Knyazev G. A. , Kuzmichev A. N. , Petrov P. E. , Vetoshko P. M. , Belotelov V. I. , Bun'kov Yu. M.
Published: April 2024

The excitation of a magnon Bose−Einstein condensate in an yttrium iron garnet film due to acoustic coupling with the condensate in the second sample is experimentally studied. A nonlinear nature of this excitation is demonstrated. The formation of a phonon Bose−Einstein condensate in the substrate is assumed. This experiment opens the possibility of creating qubits based on acoustically interacting Bose−Einstein condensates.
Spin Chaos of Exciton Polaritons in a Magnetic Field
Authors: Gavrilov S. S. , Ipatov N. N. , Kulakovskiy V. D.
Published: April 2024

The spin properties of exciton polaritons in a micropillar cavity placed in a static magnetic field and excited by a resonant light wave are studied theoretically. Owing to the Zeeman effect, a nonlinear polariton system has two branches of optical response that are characterized by opposite circular polarizations. An indirect mechanism of polarization reversal is predicted, according to which the current state of the system undergoes a transition to dynamical chaos, and then the alternative spin state is established spontaneously. Such spin switches, mediated by a chaotic stage, proceed in both directions near the same critical excitation amplitude, so that the sign of the circular polarization of the cavity radiation is directly determined by the intensity of the optical pump.
On the Separation of a Monolayer of Charged Microparticles in a Parabolic Confinement
Authors: Klumov B. A.
Published: April 2024

The evolution of an initially planar monolayer of charged microparticles in a complex plasma (plasma crystal) in horizontal (in the plane of the monolayer) and vertical parabolic confinements has been considered. The separation (buckling instability) of a Yukawa system into several layers at the weakening of the vertical confinement, as well as structural changes in such a plasma crystal, has been studied using the molecular dynamics method. In particular, it has been shown that the radial inhomogeneity of the plasma crystal qualitatively changes the character of the separation compared to homogeneous systems. Indeed, the separation begins in the center of the crystal, where the average distance between particles is minimal, and propagates in the form of a wave towards the periphery of the system at the weakening of the vertical confinement. This explains features of the behavior of plasma crystals in recent experiments with the complex plasma.
Anisotropy of the Critical Current and Abrikosov Vortex Pinning in Magnetic Superconductor EuCsFe4As4
Authors: Degtyarenko A. Yu. , Vlasenko V. A. , Kuz'micheva T. E. , Pervakov K. S. , Gavrilkin S. Yu. , Tsvetkov A. Yu. , Kuz'michev S. A.
Published: April 2024

In this study, for the first time, we present a systematic study of the critical current densityJcat two magnetic field orientationsB∥abandB∥cin a single crystal of the superconducting pnictide EuCsFe4As4, which shows a magnetic ordering belowTcand belongs to the 1144 family. The anisotropy ofJcand its temperature dependence are determined. The exponentsαof theJc(B)dependences from 0.1 to 1 T are in a good agreement with the theoretical predictions for strong Abrikosov vortex pinning, which is also confirmed by the values of the pinning strength estimated using the Dew-Hughes model.
On the Fundamental Difference between the Effects of Electrical and Mechanical Vibrations on the Dynamics of a Charge Density Wave
Authors: Nikitin M. V. , Pokrovskiy V. Ya. , Kay D. A. , Zybtsev S. G.
Published: April 2024

The effects of radio-frequency electric and strain fields on the depinning and sliding of a charge density wave in the quasi-one-dimensional conductor TaS3 have been compared. The amplitude dependence of the threshold voltage Vt (zeroth Shapiro step) has been studied for both fields. The threshold voltage Vt decreases with increasing radio-frequency electric field Erf at increasing rate |dVt/dErf|, whereas with increasing strain field, the decrease in the threshold voltage Vt is saturated, approaching a constant value. This result indicates a qualitative difference between the mechanisms of influence of the electric and strain fields on the dynamics of the charge density wave and is explained by the modulation of the sliding velocity of the charge density wave and pinning potential in the former and latter cases, respectively. In practice, the result allows one to distinguish the mechanical impact on the dynamics of the charge density wave from the influence of electrical interference at the same frequency.