bluuebunny/crossref_metadata_2025 huggingface dataset:
Modern Scanning Electron Microscopy. 2. Test objects for Scanning Electron Microscopy
Authors: Novikov Yu. A.
Published: April 2024

The review of the test objects intended for calibration of scanning electron microscopes and researches to secondary electronic emission of a relief surface of a solid state in scanning electron microscope is carried out. The test objects are divided on two parameters – kind of a relief and structure of a relief. By the form of relief the test objects are divided on single, pitch and periodic. On a structure of a relief of the test objects are divided into objects with a rectangular structure and objects with a trapezoid structure with the large and small corners of an inclination of lateral walls. The examples of such the test objects are given. Their characteristics and methods of certification of parameters are described. The advantages and lacks of the test objects are considered. Is shown, that the best characteristics have the tests objects representing pitch structures consisting of trapezoid trenches with the large corners of an inclination of lateral walls. The test objects are created in monosilicon with of a surface orientation by {100} by method liquid anisotropic etching of silicon. These test objects allow defining all characteristics scanning electron microscopes, influencing on measurement of the linear sizes of relief structures used in microelectronics and nanotechnology. With their help it is possible to carry out correlation measurements, which raise accuracy of calibration scanning electron microscopes up to ten times.
Interference Transport in a Two-Dimensional Topological Insulator in a CdHgTe Quantum Well
Authors: Ryzhkov M. S , Kozlov D. A , Khudayberdiev D. A , Kvon Z. D , Mikhaylov N. N
Published: April 2024

Interference transport in mesoscopic samples of a two-dimensional topological insulator in CdHgTe quantum wells is studied for the first time. It is established that quasi-ballistic edge transport in such an insulator exists at lengths up to 10 µm. In this transport regime, almost periodic Aharonov–Bohm oscillations caused by the formation of closed loops with a characteristic size of about 200 nm by edge states are found. The phase coherence length in the two-dimensional topological insulator is determined for the first time from the measured temperature dependence of their amplitude.
Interconnected evolution of epidemic and public vaccination opinion
Authors: Leonidov A. V , Vasilyev S. B , Vasilyeva E. E
Published: April 2024

A new model of interconnected coevolving SIRS epidemic and public vaccination opinion pattern is presented. The underlying two-layer network contains strata corresponding to physical interactions in real space and social communications. The layer corresponding to physical interactions is constructed based on data on a real network representing communications between high school students. The evolution of people vaccination attitude is described using an Ising-type model. The model describes a non-trivial dependence of resulting epidemic dynamics on (1) noise amplitude, (2) initial opinion pattern and (3) influence of external information.
Quantum Algorithm for the Invariant Estimate of the Closeness of Classical Ciphers to the One-Time Pad
Authors: Molotkov S. N
Published: April 2024

An invariant measure of the closeness of a block cipher to the perfect (ideal) cipher of the one-time pad has been proposed. The measure is the same for any implementation of the one-time pad. A quantum algorithm based on the determination of the eigenvalue (phase) of the quantum state has been proposed to estimate the closeness of the block cipher to ideal in terms of the proposed measure with high probability and accuracy.
Quasistationary Polariton States in Mesocavities
Authors: Belonovskiy A. V , Nikolaev V. V , Girshova E. I
Published: April 2024

When the strength of light–matter interaction (the Rabi splitting) in mesocavities is comparable to the energy spacing between the cavity modes, an exciton mode is coupled simultaneously to a number of optical modes. It has recently been demonstrated that a nonmonotonic dependence of the population of polariton states in mesocavities on the pump intensity is possible. Here, it is shown that an additional quasistationary state may appear in the hysteresis region and the time spent by the system in this state depends on the pump intensity.
Determination of the Most Important Parameters of a Metal Irradiated by an Ultrashort Laser Pulse
Authors: Inogamov N. A , Khokhlov V. A , Romashevskiy S. A , Petrov Yu. V , Zhakhovskiy V. V , Ashitkov S. I
Published: April 2024

Ultrashort laser pulses with a duration from several to about a thousand optical cycles have significant importance in modern science and engineering. Such a pulse transfers a metal to an excited two-temperature state with hot electrons where the temperature of the electron subsystem Te is much higher than the temperature of the ion subsystem Ti. The thermal conductivity in such systems differs from well-known reference values. The thermal conductivity κ and the energy exchange rate between the electron and ion subsystems α are the key parameters of the two-temperature model, which are still poorly studied, although studies of these parameters, particularly α, are numerous. New theoretical and experimental results that make it possible to determine the parameters κ and α for gold have been reported in this work
Pair Correlation Function of Vorticity in a Coherent Vortex
Authors: Kolokolov I. V , Lebedev V. V , Tumakova M. M
Published: April 2024

We study the correlations of vorticity fluctuations inside a coherent vortex resulting from the inverse energy cascade in two-dimensional turbulence. The presence of a coherent flow, which is a differential rotation, suppresses small-scale fluctuations of the flow, which are created by an external force, and lead to the fact that these fluctuations can be considered as non-interacting and, therefore, examined in a linear approximation. We calculate the pair correlation function of vorticity and demonstrate that it has a power-law behavior both in space and in time. The obtained results allow us to start a systematic study of the effects associated with the nonlinear interaction of fluctuations, which play an essential role on the periphery of a coherent vortex. Our results are also applicable to the statistics of a passive scalar in a strong shear flow.
Charge Density and Mobility of Charge Density Waves in the Quasi-One-Dimensional Conductor NbS3
Authors: Zybtsev S. G , Pokrovskiy V. Ya , Nikonov S. A , Mayzlakh A. A , Zaytsev-zotov S. V
Published: April 2024

Three charge density waves (CDWs), two of which are formed above room temperature, are observed in the NbS3 monoclinic phase (NbS3-II). The charge density and mobility in the high-field limit have been determined for each of three CDWs in this work using the synchronization effect of CDWs in high-frequency fields. It has been found that the mobility of each CDW in this limit is approximately equal to the normal-state mobility of quasiparticles condensed in it. Furthermore, correlation has been observed between the temperature dependences of mobilities of CDWs and quasiparticles. The results of this work refresh problems of a mechanism of the limit conductivity of CDWs and of the distribution of CDWs between atomic chains in the unit cell.
Gyrotropic Oscillations of Magnetic Vortices in Two Interacting Ferromagnetic Disks
Authors: Skorokhodov E. V , Tatarskiy D. A , Gorev R. V , Mironov V. L , Fraerman A. A
Published: April 2024

The gyrotropic motion of vortex magnetization distributions in two coupled ferromagnetic disks has been experimentally studied and numerically simulated. The dependence of the resonant frequency of the collective gyrotropic oscillation mode of vortices on the distance between the centers of disks has been studied by magnetic resonance force spectroscopy. The energy of the interaction of magnetic vortices as a function of the distance between disks has been estimated from this dependence using solutions of the Thiele equation.
Measurement of at the 250 GeV ILC
Authors: Antonov E. S. , Drutskoy A. G.
Published: April 2024

The process with the subsequent decay of the Higgs boson is studied, where both Z bosons are reconstructed in the final states with two jets. The analysis is performed using Monte Carlo data samples obtained with detailed ILD detector simulation assuming an integrated luminosity of 2 ab–1, beam polarizations of, and center-of-mass energy of GeV for the electron–positron International Linear Collider being currently designed. The analysis is repeated for the case of two 0.9 ab–1 data samples with polarizations . Contributions of the potential background processes are studied using all available ILD MC event samples. The largest background comes from the process supplemented by an energetic photon produced by initial state radiation. To suppress this background, we require that at least one of the Z bosons decays to b-jets. To reduce the jet reconstruction uncertainties the variable is used, where GeV. The distributions are obtained for the studied signal and backgrounds to estimate the expected accuracy of the measurement. The accuracy is 22% for the option of the single polarization sample described above and deteriorate to 24% in case of the sample with two polarizations. The proposed method can be applied at any future collider.
Ghost Fiber Optic 3D Endoscopy
Authors: Belinskiy A. V. , Gostev P. P. , Magnitskiy S. A. , Chirkin A. S
Published: April 2024

A new type of ghost fiber optic endoscopy has been proposed to obtain ghost images of three-dimensional optically transparent objects. The method is based on spatial and temporal correlation of light beams formed in a bundle of single-mode fibers exposed in the transverse direction to femtosecond laser pulses. Resolution in the depth of an object is ensured by an original algorithm to reconstruct images, which involves both the properties of femtosecond radiation and the features of light propagation in an inhomogeneous scattering medium. The effectiveness of the proposed method has been confirmed by a numerical simulation by an example of an octahedron with a layered structure.
On the Formation of a Plasma Cloud at the Ablation of a Pellet in a High-Temperature Magnetized Toroidal Plasma
Authors: Bakhareva O. A. , Sergeev V. Yu. , Sharov I. A.
Published: April 2024

The investigation of cold secondary plasma clouds near pellets ablating in the hot plasma of magnetic confinement devices (tokamaks and stellarators) provides valuable information on the physical characteristics of a pellet cloud. In this work, the characteristic sizes of emitting clouds around fusible polystyrene pellets and refractory carbon pellets have been analyzed. The calculation of the ionization length of C+ ions in both carbon and hydrocarbon clouds has shown that the contribution of only hot electrons is insufficient to ensure the experimentally observed decay lengths of the CII line intensity. Taking into account the strong shielding of the electron flux of the background plasma in the hydrocarbon pellet cloud, the ionization of C+ ions in this cloud is determined predominantly by electrons of the cold plasma of the cloud. Shielding near a refractory carbon pellet is weak because its ablation rate is lower. The contributions from hot electrons of the surrounding plasma and cold electrons of the pellet cloud to the ionization of C+ ions are comparable in the case of carbon pellets.
Multicomponent Current Sheet of the Magnetopause with an Arbitrary Energy Distribution of Particles
Authors: Nechaev A. A. , Kocharovskiy Vl. V. , Kocharovskiy V. V. , Garasev M. A.
Published: April 2024

An exact solution to the Maxwell–Vlasov equations has been found for a large class of multicomponent current sheets in collisionless plasma, which describe the spatial structure of the current in the magnetopause and consistent inhomogeneous anisotropic momentum distributions of particles with different effective temperatures. Devised sheets allow a nonmonotonic variation of the magnetic field and can have asymmetric, multihump, and sign-alternating profiles of the current density. Profiles of the current of different particle populations can have different scales, contain countercurrents, and be spatially shifted with respect to each other. The model under consideration is applicable to qualitatively describe a magnetopause separating a magnetosphere of a planet from a solar wind or separating regions of the solar wind with different parameters of the plasma and magnetic field.
Effect of Disorder on Magnetotransport in Semiconductor Artificial Graphene
Authors: Tkachenko O. A. , Tkachenko V. A. , Baksheev D. G. , Sushkov O. P.
Published: April 2024

Magnetotransport in mesoscopic samples with semiconductor artificial graphene has been simulated within the Landauer–Büttiker formalism. Model four-terminal systems in a high-mobility two-dimensional electron gas have a square shape with a side of 3–5 μm, which is filled with a short-period (120 nm) weakly disordered triangular lattice of antidots at the modulation amplitude of the electrostatic potential comparable with the Fermi energy. It has been found that the Hall resistancein the magnetic field range of B = 10–50 mT has a hole plateau, where R0 = h/2e2 = 12.9 kΩ, at carrier densities in the lattice below the Dirac point n n1D and an electron plateauat n n1D. Enhanced disorder destroys the plateaus, but a carrier type (electrons or holes) holds. Long-range disorder at low magnetic fields suppresses quantized resistance plateaus much more efficiently than short-range disorder.
Muons in EASs with E0 = 1019 eV According to Data of the Yakutsk Array
Authors: Glushkov A. V. , Lebedev K. G. , Saburov A. V.
Published: April 2024

Lateral distribution functions of particles in extensive air showers with the energyeV recorded by ground-based and underground scintillation detectors with a threshold of @GeV at the Yakutsk array during the continuous observations from 1986 to 2016 have been analyzed using events with zenith angles θ ≤ 60°. Experimental functions have been compared to the predictions obtained with the QGSJet-01-d hadron interaction model by applying the CORSIKA code. The entire dataset indicates that cosmic rays consist predominantly of protons.
Smith–Purcell Radiation Driven by the Field of a Standing Laser Wave
Authors: Tishchenko A. A.
Published: April 2024

Smith–Purcell radiation is well known as a source of quasi-monochromatic electromagnetic radiation that occurs when fast electrons move above a diffraction grating. In this paper, we calculated the Smith–Purcell radiation generation from a flat surface along which there is a field of a standing laser wave. A periodically changing laser field induces a periodic inhomogeneity in the distribution of electrons in the near-surface layer. This periodicity, being an analogue of a diffraction grating, leads to the possibility of generating Smith–Purcell radiation. It is shown that the properties of Smith–Purcell radiation from such an unusual “light” grating are also unusual: the dispersion relation, unlike the standard for Smith–Purcell radiation, does not contain diffraction orders, so that all radiation is concentrated in one peak. The calculated effect makes it possible to control the radiation frequency or angle by changing the laser frequency and may be of interest for the development of new compact radiation sources with tunable characteristics and for non-invasive diagnostics of relativistic electron beams.
On the Laser Generation in Two-Dimensional Materials with Pumping by Quasitrapped Modes
Authors: Gubin M. Yu. , Shesterikov A. V. , Volkov V. S. , Prokhorov A. V.
Published: April 2024

A model has been proposed to describe the laser generation of two-dimensional semiconductor films with near-field pumping by quasitrapped modes excited in dielectric metasurfaces. A metastructure consisting of a Si metasurface coated with a MoTe2 film, where narrow-band resonance of a quasitrapped mode is joined with a broad exciton resonance of a two-dimensional material, has been designed. Threshold conditions for generation in the MoTe2 film with pumping by quasitrapped modes have been determined. The possibility of polarization control of the emission of the proposed metastructure has been demonstrated.
Relativistic Tunneling Ionization in Crossed Petawatt Laser Beams
Authors: Popruzhenko S. V.
Published: April 2024

A scheme is proposed for a two-beam experiment on multi-petawatt laser systems aimed at searching for relativistic effects in electron tunneling from deep levels of multiply charged ions. It is shown that the most efficient relativistic ionization will occur in the field of a standing wave that arises in the case of counter-propagating beams. Estimates are given showing that the observation of relativistic effects during the ionization of -states of hydrogen-like ions with charge is potentially possible at laser intensity in the beam overlap domain 1025 W/cm2.
Mode Structure of Supercontinuum Generated by Ultrashort Pulses in Antiresonant Hollow-Core Fibers
Authors: Savitskiy I. V. , Stepanov E. A. , Lanin A. A. , Fedotov A. B.
Published: April 2024

The mode structure of broadband radiation with the spectrum from 200 to 2500 nm, which is obtained in the process of soliton self-compression of a laser pulse in an antiresonant hollow-core fiber, has been analyzed. It has been demonstrated that the most energy-intensive infrared part of radiation from 1300 to 2500 nm, which forms a single-cycle pulse, is localized in the fundamental spatial mode LP01. Under phase matching conditions in the visible part of the supercontinuum, the third harmonic is generated near 620 nm in high‑order modes and tube modes. It has been shown that the third harmonic radiation at a wavelength of about 700 nm localized in the core of the fiber can be used to measure the phase of the field with respect to the envelope of ultrashort pulses at the output of the fiber.
“Capillary” Structures in Transversely Trapped Nonlinear Optical Beams
Authors: Ruban V. P.
Published: April 2024

A mathematical analogy between paraxial optics with two circular polarizations of light in a defocusing Kerr medium with positive dispersion, binary Bose–Einstein condensates of cold atoms in the phase separation regime, and hydrodynamics of two immiscible compressible liquids can help in theoretical search for unknown three-dimensional coherent optical structures. In this work, transversely trapped (by a smooth profile of the refractive index) light beams are considered and new numerical examples are presented, including a “floating drop,” a precessing longitudinal optical vortex with an inhomogeneous profile of filling with the second component, and the combination of a drop and a vortex filament. Filled vortices that are perpendicular to the beam axis and propagate at large distances have also been simulated.
Inverse “Foldover” Resonance in an Yttrium Iron Garnet Film
Authors: Bun'kov Yu. M. , Vetoshko P. M , Safin T. R. , Tagirov M. S.
Published: April 2024

Nonlinear magnetic resonance is studied in an in-plane magnetized yttrium iron garnet (YIG) film. For YIG films magnetized perpendicular to the plane, the effect referred to as the foldover resonance is well known. It arises because the precession frequency increases with the deviation of the magnetization. When the field is reduced, the frequency of the precession remains resonant because the demagnetizing field decreases with the deviation of the magnetization. The signal disappears when the radio frequency pump power is insufficient to maintain a nonequilibrium state of the system. In the in-plane magnetized yttrium iron garnet film, the precession frequency decreases with an increase in the pump amplitude. Accordingly, the foldover effect arises under an increase in the field. The fundamental difference is that the precession in the latter case should be unstable with respect to the decay into spin wave modes. The deviation angles of magnetization of about 10° are reached, and the rate of decay of the uniform precession into spin waves, which depends on the deviation angle of the magnetization, is measured. This study opens up another way of achieving the magnon density corresponding to the formation of its Bose–Einstein condensate.
Channels of Filaments of Axially Asymmetric Optical Vortices at a Wavelength of 1800 nm in a LiF Crystal
Authors: Shlenov S. A , Kompanets V. O , Kandidov V. P , Chekalin S. V , Vasil'ev E. V
Published: April 2024

The formation of a set of filaments and plasma channels in a femtosecond optical vortex has been studied experimentally and numerically. A longitudinal distribution of color center tracks with a length of 1 cm written in a LiF crystal by an axially asymmetric beam in the single-pulse regime has been detected experimentally for the first time. It has been shown that, at a sufficient excess of the peak power over the critical value, two hot points on the annular profile of vortex beam separated by the phase dislocation region form sequences of color center tracks; each sequence in the cross section of the beam is localized near the initial hot point. Secondary filaments and the corresponding tracks appear with an increase in the pulse energy. The parameters of femtosecond filaments in LiF have been numerically estimated.
Observation of Spatiotemporal Self-Compression of Pulses in One-Dimensional Waveguide Arrays Fabricated by Laser Writing
Authors: Arkhipova A. A , Zhuravitskiy S. A , Skryabin N. N , D'yakonov I. V , Kalinkin A. A , Kulik S. P , Chekalin S. V , Kartashov Ya. V , Zadkov V. N
Published: April 2024

The features of nonlinear propagation of high-intensity pulses in the short-wavelength infrared range in extended one-dimensional waveguide arrays with different spatial periods, formed in fused silica by laser writing, are studied. More than tenfold self-compression of femtosecond pulses up to a duration of several periods of the light field is experimentally observed.
Fine Structure of the 3T1(3H) → 5E(5D) Transition in the Fe2+ Ion in Iron-Doped Zinc Selenide
Authors: Krivobok V. S , Aminev D. F , Onishchenko E. E , Ushakov V. V , Chentsov S. I , Zazymkina D. A
Published: April 2024

Zero-phonon components of the 3T1(3H) → 5E(5D) transition between inner shells of the Fe2+ ion have been detected in low-temperature photoluminescence spectra of Fe-doped ZnSe crystals. Six spectral components corresponding to dipole-allowed transitions between the components 3T1(3H) and 5E(5D) of the fine structure, which is caused by the spin–orbit coupling, have been reliably detected at temperatures of 5–10 K. The electronic spectrum of the Fe2+ ion in the ZnSe matrix has been refined using the data obtained.
Specific Features of Landau Level Mixing and the Electron Distribution Function under Conditions of the Quantum Hall Effect
Authors: Van'kov A. B
Published: April 2024

The electron distribution over Landau levels is calculated in the regime of the quantum Hall effect at strong Coulomb interaction. For this purpose, a modified scheme of exact diagonalization with a significantly reduced basis of many-particle configurations has been developed, which makes it possible to adequately take into account the mixing of states in several Landau levels. The behavior of the electron distribution function over Landau levels is studied as a function of the filling factor and the Wigner–Seitz radius rs. It is shown that the Landau quantization at a fixed electron density significantly suppresses the smearing of the electron distribution function as compared to the case of zero magnetic field. For example, for rs 1 and low filling factors, the quasiparticle contribution to the Migdal jump 1 − Z in the distribution function is an approximately linear function of ν and a quadratic function of rs. Simultaneously, as ν decreases, the tails of the distribution function become longer. The mechanism of rearrangement of the distribution function in the regime of the quantum Hall effect is described in terms of the generation of magnetoplasmon fluctuations involved in the structure of the ground state of the system.
Band Structure of Bilayer Graphene Intercalated by Potassium Atoms. Ab Initio Calculations
Authors: Akhmatov Zeytun A. , Akhmatov Zarif A.
Published: April 2024

Using the electron density functional theory, the electronic band structure of pure and potassium-intercalated bilayer graphene has been studied. It is shown that after the intercalation process, a band gap appears in the band structure of bilayer graphene. In addition, the energy gap changes nonlinearly depending on the intercalate concentration in the interlayer space of bilayer graphene. We also calculated the energy spectra of bilayer graphene containing vacancy defects, the presence of which leads to the appearance of mid-gap states.
Liquid–Crystal Structure Inheritance in Machine Learning Potentials for Network-Forming Systems
Authors: Balyakin I. A , Ryl'tsev R. E , Shchelkachev N. M
Published: April 2024

It has been studied whether machine learning interatomic potentials parameterized with only disordered configurations corresponding to liquid can describe the properties of crystalline phases and predict their structure. The study has been performed for a network-forming system SiO2, which has numerous polymorphic phases significantly different in structure and density. Using only high-temperature disordered configurations, a machine learning interatomic potential based on artificial neural networks (DeePMD model) has been parameterized. The potential reproduces well ab initio dependences of the energy on the volume and the vibrational density of states for all considered tetra- and octahedral crystalline phases of SiO2. Furthermore, the combination of the evolutionary algorithm and the developed DeePMD potential has made it possible to reproduce the really observed crystalline structures of SiO2. Such a good liquid–crystal portability of the machine learning interatomic potential opens prospects for the simulation of the structure and properties of new systems for which experimental information on crystalline phases is absent.
Optical Modes in Elliptical Microcavities for Single-Photon Sources
Authors: Kazanov D. R , Monakhov A. M
Published: April 2024

A theory of optical modes in an elliptical microcavity has been developed using Mathieu functions in elliptical coordinates. A key difference from the circular case is the splitting of doubly degenerate modes. Split optical modes have been numerically calculated and their symmetry has been determined. A method has been proposed to choose the parameters of a cavity for a certain wavelength. The difference between the energies of optical modes in the cavity with metallic walls and in the dielectric cavity is no more than ~20%. The dispersion relations of optical modes show the possibility of degeneracy of modes with different symmetries, which allows the spectral and polarization filtering of radiation of single-photon sources and the fabrication of sources of multiply entangled states.
Measurement of the Thermal Conductivity of Carbon Nanowalls by the 3ω Method
Authors: Chernodubov D. A , Bondareva Yu. V , Shibalov M. V , Mumlyakov A. M , Zhdanov V. L , Tarkhov M. A , Maslakov K. I , Suetin N. V , Kvashnin D. G
Published: April 2024

Carbon nanowall films with different thicknesses have been obtained by chemical deposition from a gas phase in a dc discharge. The thermal conductivity of the resulting structures has been measured for the first time using the 3ω method in the temperature range of 280–310 K. It has been shown that the thermal conductivity of walls depends on their thickness. The thermal conductivity of 1-μm carbon nanowalls is 6.9 W m–1 K–1. The results obtained in this work are necessary to design electro-optical devices based on carbon nanowalls.
Genesis of Collective Excitations in the Conductivity Spectra of Higher Borides RB6 and RB12 Exhibiting a Cooperative Structural Instability
Authors: Makrushin M. A , Arseev P. I , Krasikov K. M , Kadyrov L. S , Zhukova E. S , Sluchanko N. E
Published: April 2024

To describe anomalies in the ac conductivity spectra of higher borides RB6 and RB12 with the Jahn−Teller structural instability, a model based on the dipole nature of the effect of collective lattice vibrations on electron transport is proposed. The simulation results are compared with the measured spectra, and the crystallographic parameters are estimated.
New Objects in Scattering Theory with Symmetries
Authors: Losev A. S , Sulimov T. V
Published: April 2024

We consider 1D quantum scattering problem for a Hamiltonian with symmetries. We show that the proper treatment of symmetries in the spirit of homological algebra leads to new objects, generalizing the well-known T- and K-matrices. Homological treatment implies that old objects and new ones are to be combined in a differential. This differential arises from homotopy transfer of induced interaction and symmetries on solutions of free equations of motion. Therefore, old and new objects satisfy remarkable quadratic equations. We construct an explicit example in SUSY QM on a circle demonstrating nontriviality of the above relation.
High-Quality Infrared Metalenses Based on Germanium Dimers
Authors: Pustynnikova V. M , Musorin A. I , Fedyanin A. A
Published: April 2024

Modern methods of nanophotonics allow creating miniature devices that change the direction of light propagation, modulate the phase front, and control the outcoming state of the polarization. One of the promising areas of research is the development of flat optics elements based on planar analogues of metamaterials—dielectric metasurfaces, which are two-dimensional arrays of subwavelength nanoparticles with a high refractive index and low absorption coefficient. However, the resonances of such nanoscatterers have usually a low quality factor. Symmetry breaking of particle can lead to the excitation of a high-Q quasi-bound states in the continuum. In this work, we numerically study infrared metasurfaces that support such resonances and are formed by dimers of germanium nanocuboids. The possibility of focusing radiation to a point and line by 300‑nm-thick spherical and cylindrical metalenses is shown.
Rotating Temperature Wave in a Thin Water Layer
Authors: Kerekelitsa I. V , Martyushev L. M
Published: April 2024

The convective motion of water in a small cylindrical container, where the bottom and walls are heated and maintained at a constant temperature and heat is removed from the top surface, has been studied numerically. The no-slip condition is specified at the water–air interface to simulate the effect of a thin absorption film. A temperature wave, which rotates in parallel to the surface at an angular velocity of (0.06 ± 0.02) rad/s, has been detected for the first time in this system. This wave is high-mode, has a frequency of about 0.1 Hz, and is observed in very narrow ranges of the dimensions of the container and temperatures.
Three-Dimensional H–φ–θ Phase Diagram of ErB12 Antiferromagnet with Dynamic Charge Stripes
Authors: Krasikov K. M , Bogach A. V , Shitsevalova N. Yu , Filippov V. B , Sluchanko N. E
Published: April 2024

A three-dimensional (H, φ, θ, T = 2 K) magnetic phase diagram has been constructed for the first time for the antiferromagnetic metal Er11B12 with an amplitude-modulated magnetic structure exhibiting an electronic instability (dynamic charge stripes). The boundaries determining the shape of the main magnetic phases in the H–φ–θ space are reconstructed from measurements of the magnetoresistance. The role of dynamic charge stripes, which suppress the indirect Ruderman–Kittel–Kasuya–Yoshida exchange between the magnetic moments of the nearest Er3+ ions, and of the single-ion anisotropy in the formation of a complicated multicomponent phase diagram of Er11B12 is discussed.
Sequence of Three-, Two-, and One-Dimensional Structures Formed from a Cholesteric Liquid Crystal at Change in the Chirality
Authors: Baklanova K. D , Dolganov V. K , Kats E. I , Dolganov P. V
Published: April 2024

In this work the formation of modulated structures in chiral liquid crystals is studied. For different chiral nematics that at low temperature form the usual (with twist in one direction) cholesteric phase, we found that at high temperature in the vicinity of the phase transition into isotropic liquid a universal sequence of structural transformations is observed. Planar cholesteric transforms at short helical pitch into the three-dimensional phases with cubic symmetry (Blue Phases), in two-dimensional structure at intermediate helical pitch and in one-dimensional structure in the plane of the sample at large pitch. The structures possess periodic orientational and translational order on scales much larger than molecular scale. Optical measurements were made on ordered structures obtained near the transition temperature to the isotropic phase. Possible reasons of formation of the structures are discussed on the basis of existing experimental data and theoretical considerations.
Ultrasonic Spin Echo Caused by Irreversible Phase Relaxation
Authors: Sazonov S. V
Published: April 2024

The possibility of the generation of a primary ultrasonic echo in the system of equidistant Zeeman triplets owing to irreversible phase relaxation has been predicted. The disappearance of phase relaxation results in the disappearance of an echo signal. This effect is due to the destructive interference of two allowed quantum transitions emitting in antiphase. The difference between the phase relaxation times at these transitions leads to an incomplete quenching of resulting coherence, leading to generation of the echo signal.
Resistive Switching Effect in TaN/HfOx/Ni Memristors with a Filament Formed under Local Electron-Beam Crystallization
Authors: Voronkovskiy V. A , Gerasimova A. K , Aliev V. Sh
Published: April 2024

The influence of an intense electron beam on a nonstoichiometric oxide HfOx (х@) layer of a TaN/HfOx/Ni memristor on its electrophysical properties is studied. It is found that the crystalline h-Hf, m‑HfO2, o-HfO2, and t-HfO2 phases are formed in the HfOx film under this impact. It is established that memristors demonstrate resistive switching at certain electron fluence values. At the same time, such memristors have resistive switching voltages several times lower than those of unirradiated memristors. In addition, they exhibit a multiple decrease in the spread of resistive switching voltages, as well as resistances in low- and high-resistance states. The current–voltage curves of the obtained memristors indicate that the charge transport in them is described by the space-charge-limited current mechanism.
Acoustic metric and Planck constants
Authors: Volovik G. E
Published: April 2024

Based on Akama–Diakonov (AD) theory of emergent tetrads, it was suggested that one can introduce two Planck constants,and, which are the parameters of the corresponding components of Minkowski metric,. In the Akama–Diakonov theory, the intervalis dimensionless, as a result the metric elements and thus the Planck constants have nonzero dimensions. The Planck constanthas dimension of time, and the Planck constanthas dimension of length. It is natural to comparewith the Planck length. However, this connection remains an open question, because the microscopic (trans-Planckian) physics of the quantum vacuum is not known. Here we study this question using the effective gravity emerging for sound wave quanta (phonons) in superfluid Bose liquid, where the microscopic physics is known, and the elements of the effective acoustic metric are determined by the parameters of the Bose liquid. Since the acoustic interval is dimensionless, one may introduce the effective “acoustic Planck constants.” The acoustic Planck constanthas dimension of length and is on the order of the interatomic distance. This supports the scenario in which. We also use the acoustic metric for consideration of dependence ofon the Hubble parameter in expanding Universe.
Generation of Intense Few-Cycle Terahertz Radiation in Organic Crystals Pumped by 1.24-μm Multigigawatt Chirped Laser Pulses
Authors: Rumyantsev B. V , Pushkin A. V , Suleymanova D. Z , Zhidovtsev N. A , Potemkin F. V
Published: April 2024

It has been shown that the spectrum of intense few-cycle terahertz radiation generated in a DAST organic crystal can be controlled by chirping 1.24-μm pump femtosecond laser radiation of a chromium forsterite laser system. It has been found that an increase in the linear chirp of generating radiation results in the narrowing of the spectrum of terahertz radiation and its redshift. The simulation of the generation of terahertz radiation within the model of three-wave mixing has shown that this effect is due to a change in the phase matching width of the degenerate generation of the difference frequency of terahertz range. In addition, the comparative analysis of terahertz radiation spectra generated in DAST, DSTMS, OH1, and BNA organic crystals indicates that the spectral–temporal properties of terahertz radiation can be more roughly controlled by choosing an appropriate crystal. The proposed approach to control the terahertz radiation spectrum by chirping the pump pulse provides the foundation for spectroscopic studies using intense terahertz radiation with controlled spectral–temporal properties.
Radiation of a Solitary Polarization Pulse Moving at the Speed of Light
Authors: Arkhipov R. M , Arkhipov M. V , Pakhomov A. V , D'yachkova O. O , Rozanov N. N
Published: April 2024

Photons have zero rest mass and always travel at the speed of light in a vacuum, but have no dipole moment. Atoms and molecules, which may have a constant or variable dipole moment, have mass and therefore cannot move at or above the speed of light. As a result, the radiation from such systems moving at the velocity of light was not considered. However, it is possible to create many artificial objects (light spots, effective charges, current pulses, etc.) that can travel at the speed of light and even exceed it. In this case, they become a source of electromagnetic radiation. In this work, the radiation of a solitary polarization pulse that travels at the speed of light and has a variable or constant amplitude is discussed. It is shown that if the amplitude does not change, then such an object does not radiate outward; i.e., the field emitted by it remains completely localized inside the moving polarization pulse. If the amplitude changes over time, then it begins to radiate backwards. In this case, unipolar pulses of an unusual shape, such as a rectangular one, can be obtained.
Coulomb correlations and electronic structure of CuCo2S4: a DFT + DMFT study
Authors: Skornyakov S. L , Trifonov I. O , Anisimov V. I
Published: April 2024

By employing a combined method of density functional theory and dynamical mean-field theory (DFT + DMFT) we study the spectral properties and local moment formation in the normal state of a Co-based superconductor CuCo2S4. The obtained quasiparticle mass enhancementis smaller than that in iron-based parent compounds indicating weak correlations in the Costates. We show that the mass enhancement is accompanied by an insignificant renormalization and shift of the bands in the vicinity of the Fermi level. This subtle modification is sufficient to induce a substantial transformation of one of the Fermi surface sheets and occurs due to the presence of shallow Fermi surface pockets in the electronic structure of CuCo2S4. The calculated local and fluctuating moments are smaller than those in iron-based superconductors questioning the importance of spin fluctuations for understanding the pairing mechanism of CuCo2S4.
Multiple Andreev Reflection Effect Spectroscopy of Underdoped NaFe1 – xCoxAs Single Crystals
Authors: Kuz'michev S. A , Morozov I. V , Shilov A. I , Rakhmanov E. O , Kuz'micheva T. E
Published: April 2024

We study the structure of the superconducting order parameter in underdoped NaFe1 – xCoxAs pnictides with Tc ≈ 19–21 K related to the 111 family. Using incoherent multiple Andreev reflection effect spectroscopy of planar break junctions, we directly determine the magnitudes of the two microscopic superconducting order parameters: the small superconducting gap ΔS(0), and possible edges of the large gap ΔL(0) having an anisotropy in theplane at T ≪ Tc, the corresponding characteristic ratios, as well as their temperature dependences. Additionally, we detect features of the tunneling spectra in NaFe1 – xCoxAs at, those irrelative to superconducting state, and discuss their origin.
Magnetic Properties of an SrMnO3/La0.7Sr0.3MnO3 Heterostructure on an NdGaO3 Substrate
Authors: Shaykhulov T. A , Safin A. R , Stankevich K. L , Matasov A. V , Temiryazeva M. P , Vinnik D. A , Zhivulin V. E , Nikitov S. A
Published: April 2024

An epitaxial heterostructure based on strontium and lanthanum-strontium manganite films (and @) is studied. Ferromagnetic resonance spectra, angular dependences of the resonance field for different temperatures, in-plane and cubic anisotropy as well as the temperature dependences of the magnetization, were measured. The obtained magnetic parameters of the heterostructure were compared with the magnetic parameters of a single @ film. We assume that the existence of an interlayer exchange at the ferromagnet-antiferromagnet interface at low temperatures leads to the appearance of unidirectional anisotropy in the heterostructure @/@. We believe that the presented results will be useful for the practical development of antiferromagnet-based ultrafast devices: emitters, amplifiers, detectors.
Robust Ferrimagnetism in Quasi-Freestanding Graphene
Authors: Rybkin A. G , Tarasov A. V , Gogina A. A , Eryzhenkov A. V , Rybkina A. A
Published: April 2024

The influence of the size of dislocation loops on sublattice ferrimagnetism in graphene is studied. It is shown that graphene and the underlying gold layer with Au/Co dislocation loops of various sizes are characterized by ferrimagnetic ordering within atomic layers. Additional gold adatoms under graphene enhance the induced Rashba spin–orbit coupling in graphene but do not destroy the ferrimagnetic order in graphene. Since gold clusters can remain during the intercalation of gold on the surface of graphene and under graphene, the number and size of clusters after intercalation can be controlled to enhance the induced Rashba interaction and to obtain a topological phase in graphene.
Formation of a High-Energy Particle Beam by Means of Focusing Crystal Devices
Authors: Britvich G. I , Kostin M. Yu , Pitalev V. I , Poluektov I. V , Sandomirskiy Yu. E , Chesnokov M. Yu , Chesnokov Yu. A , Yanovich A. A
Published: April 2024

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.
Muon Puzzle in Ultra-High Energy EASs According to Yakutsk Array and Auger Experiment Data
Authors: Glushkov A. V , Saburov A. V , Ksenofontov L. T , Lebedev K. G
Published: April 2024

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
Authors: Khayrulin I. R , Antonov V. A , Ryabikin M. Yu
Published: April 2024

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.
Stability of Solid Atomic Nitrogen Phases at Atmospheric Pressure
Authors: Grishakov K. S , Degtyarenko N. N
Published: April 2024

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 theand Pccn crystal symmetries are unstable to the formation of vacancies at atmospheric pressure. Theand 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
Authors: Timofeev V. E , Aristov D. N
Published: April 2024

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.