Новые публикации

https://doi.org/10.48550/arXiv.2311.05995

We revisit the problem of two-terminal transport of non-interacting Fermi particles across the tight-binding chain by employing the semi-microscopic model for the contacts, where we mimic the self-thermalization property of the contacts by using the Lindblad relaxation operators. It is argued that the dissipative dynamics of the contacts can essentially modify the line-shape of resonant peaks as compared to the Landauer-Büttiker theory. We also address the effect of this dissipative dynamics, which we refer to as external decoherence, on particle transport in disorder chains. It is shown that external decoherence reduces conductance fluctuations but does not affect the Anderson localization length.

https://doi.org/10.1016/j.ceramint.2023.09.322

Herein, the strategy of replacing Ge⁴⁺ with smaller Si⁴⁺ was adopted to realize the site-selective occupation of Bi³⁺ activator in the small ring and obtain a near-infrared light-emitting in Zn₂(Ge,Si)O₄. The designed phosphor exhibits a broad NIR emission with FWHM ≈104 nm in the 650−860 nm region, with a center emission wavelength of about 750 nm. Interestingly, the more sensitive four-member ring sites gradually replaced the six-member ring sites and realized a large-scope photoluminescence regulation from blue to NIR by just after the crystal field engineering. The possible reasons for this phenomenon can be interpreted by centroid shift (ε_c) and crystal field splitting (ε_cfs). This work not only provides new insights for the development of Bi³⁺-activated NIR-emitting phosphors, but also provides thoughts for revealing the potential NIR luminous mechanism of Bi³⁺.

https://doi.org/10.1063/5.0173550

We find numerically the complex eigenvalues in grating composed of infinitely long silicon rods of rectangular cross section and show existence of exceptional points (EPs) in parametric space of structural scales and wave vector along the rods. The EPs have sufficiently small imaginary parts due to their proximity to bound states in the continuum. This enables to trace the resonant frequencies in the transmission around the EP and, accordingly, to identify the EP by bifurcation of the transmission. We present generic coupled mode theory to elucidate this effect. We also show that structural fluctuations of grating preserve EP but obscures their observation because of inhomogeneous broadening of transmission peaks.

 https://doi.org/10.1002/pssr.202300336

The utilization of graphene on silicon carbide (SiC) substrates holds substantial promise for advancements in spintronics and nanoelectronics. Furthermore, incorporating magnetic metals provides an optimal framework for probing fundamental physical phenomena. The approach to developing such systems is in situ intercalation of graphene with magnetic metals. Herein, the electronic structure is analyzed and the magnetic properties of the system are synthesized by the thermal decomposition of 6H-SiC(0001) surface and subsequent intercalation of graphene with cobalt (Co) and iron (Fe) atoms. X-ray photoemission spectroscopy and low-energy electron diffraction are employed to control the synthesis and metal intercalation processes. The morphological characteristics of the synthesized system are studied by means of atomic force microscopy. The findings derived from magneto-optic Kerr effect measurements reveal a homogeneous ferromagnetic ordering at room temperature. Angle-resolved photoemission spectroscopy is used to ascertain the impact of intercalation on graphene's electronic structure. The results of this study are essential for the development of graphene-based spintronics and nanoelectronic devices as well as for fundamental studies in magnetic graphene systems.

 https://doi.org/10.1029/2023JA031665

A quantitative model of the magnetosheath (MS) magnetic structure is developed, using a multi-year set of Geotail, Themis, Cluster, and MMS magnetometer and plasma instrument data. The MS database is created using an identification algorithm, based on observed magnetic field magnitudes and proton densities, normalized by their concurrent interplanetary values, followed by additional filtering with the help of standard bow shock (BS) and magnetopause (MP) models. The model architecture is based on the toroidal/poloidal formalism and a coordinate system that naturally accounts for the tailward flaring of both boundaries. The magnetic field expansions include 960 free coefficients, derived by fitting the model to a grand data set, split into independent training and validation subsets with 1,291,380 and 411,933 1-min records, respectively. The model faithfully reproduces basic types of the interplanetary magnetic field (IMF) wrapping around the MP. Regular IMF sectors result in strongly dawn-dusk asymmetric draping, with much larger magnitudes at the quasi-perpendicular dusk side of BS, and weaker at the quasi-parallel dawn side, where the MS field lines are bent and dragged tailward. Except in the case of the flow-aligned IMF orientation, the subsolar field steadily grows toward the MP, and the effect is clearly IMF Bz-dependent: the field and its gradient are larger (smaller) for northward (southward) IMF B_z, implying a pile-up of the magnetic flux in the first case and stronger reconnection in the second. Model distributions of the MS field magnitude reveal local depressions, associated with polar cusps near the high-latitude limits of data coverage.

DOI: 10.3367/UFNe.2022.05.039195

We present experimental and theoretical results of spin crossover studies in magnetically ordered materials. The effect of spin crossovers on the electronic structure of transition metal oxides and on the Bose condensation of spin excitons in the vicinity of the spin crossover is considered. A new method for calculating the interatomic superexchange interaction in transition metal oxides is discussed that allows considering selective contributions of excited magnetic cation terms. Changes in the exchange interaction sign are predicted for spin crossovers for d⁵—d⁷ ions. In the RCoO₃ family of rare-earth cobaltites, the ground state is nonmagnetic, but, as the temperature increases, thermal excitations of high-spin states give rise to a number of experimentally detectable features. In defective RCoO₃ samples, stabilization of the high-spin term and ferromagnetic ordering are possible. Dynamical crossovers under external pumping and the dynamics of multiplicity, magnetization, and local lattice distortions are discussed. Geophysical implications of spin crossovers are considered, and metallic properties of Earth's mantle at a depth of 1400—1800 km are predicted.

https://doi.org/10.3390/nano13222925

The effect of the aluminum layer on the kinetics and mechanism of aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) in (Al/a-Si)_n multilayered films was studied using a complex of in situ methods (simultaneous thermal analysis, transmission electron microscopy, electron diffraction, and four-point probe resistance measurement) and ex situ methods (X-ray diffraction and optical microscopy). An increase in the thickness of the aluminum layer from 10 to 80 nm was found to result in a decrease in the value of the apparent activation energy E_a of silicon crystallization from 137 to 117 kJ/mol (as estimated by the Kissinger method) as well as an increase in the crystallization heat from 12.3 to 16.0 kJ/(mol Si). The detailed kinetic analysis showed that the change in the thickness of an individual Al layer could lead to a qualitative change in the mechanism of aluminum-induced silicon crystallization: with the thickness of Al ≤ 20 nm. The process followed two parallel routes described by the n-th order reaction equation with autocatalysis (Cn-X) and the Avrami–Erofeev equation (An): with an increase in the thickness of Al ≥ 40 nm, the process occurred in two consecutive steps. The first one can be described by the n-th order reaction equation with autocatalysis (Cn-X), and the second one can be described by the n-th order reaction equation (Fn). The change in the mechanism of amorphous silicon crystallization was assumed to be due to the influence of the degree of Al defects at the initial state on the kinetics of the crystallization process.

https://doi.org/10.1038/s42254-023-00659-z

Acoustic resonances in open systems, which are usually associated with resonant modes characterized by complex eigenfrequencies, play a fundamental role in manipulating acoustic wave radiation and propagation. Notably, they are accompanied by considerable field enhancement, boosting interactions between waves and matter, and leading to various exciting applications. In the past two decades, acoustic metamaterials have enabled a high degree of control over tailoring acoustic resonances over a range of frequencies. Here, we provide an overview of recent advances in the area of acoustic resonances in non-Hermitian open systems, including Helmholtz resonators, metamaterials and metasurfaces, and discuss their applications in various acoustic devices, including sound absorbers, acoustic sources, vortex beam generation and imaging. We also discuss bound states in the continuum and their applications in boosting acoustic wave–matter interactions, active phononics and non-Hermitian acoustic resonances, including phononic topological insulators and the acoustic skin effect.

DOI 10.1088/1402-4896/ad05ed

The kinetic characteristics of the doped Mott-Hubbard material are considered within the realistic spin-fermion model which takes into account the strong spin-charge coupling. The kinetic equation constructed on the basis of the mechanism of carrier scattering on the spin fluctuations is solved using the multi-moment method, which allows one to analyze the temperature behavior of nonequilibrium distribution function in the problems of electrical resistivity ρ and the Hall coefficient R_H. The calculated dependences ρ(T) and R_H(T) for the underdoped and optimally doped regimes demonstrate good qualitative agreement with the experimental data. In particular, the Hall coefficient calculated for the underdoped regime reproduces the experimentally observed sharp drop and even a change in sign at low temperatures.

 https://doi.org/10.1002/pssr.202300336

The utilization of graphene on silicon carbide (SiC) substrates holds substantial promise for advancements in spintronics and nanoelectronics. Furthermore, incorporating magnetic metals provides an optimal framework for probing fundamental physical phenomena. The approach to developing such systems is in situ intercalation of graphene with magnetic metals. Herein, the electronic structure is analyzed and the magnetic properties of the system are synthesized by the thermal decomposition of 6H-SiC(0001) surface and subsequent intercalation of graphene with cobalt (Co) and iron (Fe) atoms. X-ray photoemission spectroscopy and low-energy electron diffraction are employed to control the synthesis and metal intercalation processes. The morphological characteristics of the synthesized system are studied by means of atomic force microscopy. The findings derived from magneto-optic Kerr effect measurements reveal a homogeneous ferromagnetic ordering at room temperature. Angle-resolved photoemission spectroscopy is used to ascertain the impact of intercalation on graphene's electronic structure. The results of this study are essential for the development of graphene-based spintronics and nanoelectronic devices as well as for fundamental studies in magnetic graphene systems.

 https://doi.org/10.3390/cryst13071128

Structural features of new mixed bismuth-containing samarium iron–aluminium borate single crystals Sm_1−xBi_xFe_3−yAl_y(BO₃)₄ (x = 0.05–0.07, y = 0–0.28) were studied using X-ray diffraction analysis based on aluminium content and temperature in the range 25–500 K. The crystals were grown using the solution-in-melt technique with Bi₂Mo₃O₁₂ in a flux. The composition of the single crystals was analyzed using energy-dispersive X-ray fluorescence and energy-dispersive X-ray elemental analysis. Temperature dependencies of Sm_1−xBi_xFe_3−yAl_y(BO₃)₄ unit-cell parameters were studied. Negative thermal expansion was identified below 100 K and represented by characteristic surfaces of the thermal expansion tensor. (Sm,Bi)–O, (Sm,Bi)–(Fe,Al), (Fe,Al)–(Fe,Al), and (Fe,Al)–O interatomic distances decreased with the addition of aluminium atoms. An increase in the (Fe,Al)–(Fe,Al) intrachain bond length at low temperatures in the magnetically ordered state weakened this bond, whereas a decrease in the (Fe,Al)–(Fe,Al) interchain distance strengthened super-exchange paths between different chains. It was found that the addition of aluminium atoms influenced interatomic distances in Sm_1−xBi_xFe_3−yAl_y(BO₃)₄ much more than lowering the temperature from 293 K to 25 K. The effect of aluminium doping on magnetoelectric properties and structural symmetry of rare-earth iron borates is also discussed.

https://doi.org/10.5194/tc-17-4155-2023

From 2015 to 2020, using the spectral gradient radiometric method, the possibility of the frozen/thawed (FT) state identification of tundra soil was investigated based on Soil Moisture Active Passive (SMAP) and Global Change Observation Mission – Water Satellite 1 (GCOM-W1) satellite observations of 10 test sites located in the Arctic regions of Canada, Finland, Russia, and the USA. It is shown that the spectral gradients of brightness temperature and reflectivity (measured in the frequency range from 1.4 to 36.5 GHz with horizontal polarization, a determination coefficient from 0.775 to 0.834, a root-mean-square error from 6.6 to 10.7 d and a bias from −3.4 to +6.5 d) make it possible to identify the FT state of the tundra topsoil. The spectral gradient method has a higher accuracy with respect to the identification of the FT state of tundra soils than single-frequency methods based on the calculation of polarization index.

https://doi.org/10.3390/cryst13101415

Multicomponent flux systems based on both Li₂WO₄-B₂O₃-Li₂O-CuO-Cr₂O₃ and Bi₂O₃-MoO₃-B₂O₃-Na₂O-CuO-Cr₂O₃ were studied in order to grow Cu₂CrBO₅ crystals. The conditions for Cu₂CrBO₅ crystallization were investigated by varyingthe component ratios, and the peculiarities of their interaction were characterized by studying the formation sequence of high-temperature crystallizing phases. Special attention was paid to the problem of Cr₂O₃ solubility. Phase boundaries between CuCrO₂, Cu₂CrO₄, and Cu₂CrBO₅ were considered. The crystal structure of the obtained samples was studied viasingle crystal and powder X-ray diffraction. The chemical composition of the grown crystals was examined using the EDX technique. Anactual ratio of Cu:Cr = 1.89:1.11 was found for Cu₂CrBO₅ grown from the lithium-tungstate system, which showed a small deviation from 2:1, implying the presence of a part of bivalent Cr²⁺ in the samples. Anomalies in the thermal dependence of magnetization were analyzed and compared with the previously obtained data for Cu₂CrBO₅. The anomaly at T_C ≈ 42 K and the antiferromagnetic phase transition at T_N ≈ 119 K were considered. Polarized Raman spectra of Cu₂CrBO₅ were obtained for the first time, and a comparative analysis of the obtained data with other monoclinic and orthorhombic ludwigites is presented. Along with the polarized room temperature spectra, the thermal evolution of Raman modes near the antiferromagnetic phase transition temperature T_N ≈ 119 K is provided. The influence of the magnetic phase transition on the Raman spectra of Cu₂CrBO₅ is discussed.

https://doi.org/10.1103/PhysRevB.108.155411

We consider thermo-optic bistability induced by a high-quality defect mode in the square array of dielectric rods. It is demonstrated that the scattering problem with an account of the variation of the dielectric constant by heating can be solved with the $T$-matrix method by introducing an explicit dependence of the permittivity of the defect rod on temperature. We found that the bistability occurs at low intensities of the incident $\text{wave}\approx 0.01\mathrm{mW}/\mu m^2$ in a square array of $7\times 7$ silicon rods with a defect rod in the middle.

https://doi.org/10.1016/j.optmat.2023.114521

Light polarization control by the chiral-nematic cell with hybrid tangential-conical boundary conditions has been studied by means of photo- and electrically induced transformations of the orientational structure. The polarization azimuth changes due to the power ratio of ultraviolet and blue radiations, at which the director twist angle in the chiral nematic varies smoothly. The light polarization ellipticity is controlled by an electric field applied perpendicular to the liquid crystal cell changing the effective anisotropy of the refractive index. The optical material under study is promising to develop the devices for the light polarization converter over the entire visible range, as well as for photo-controlled rotators of linear polarization of white light.

https://doi.org/10.1016/j.cej.2023.146179

Significant process has been made on the development of semi-artificial photosynthesis catering to the production of H₂– and CO₂– derived value-added products. But there are little reports on the application of semi-artificial photosynthetic system to nitrogen fixation areas. In this study we report the successful and highly efficient N₂ fixation in one step at room temperature and ambient pressure by constructing new semi-artificial photosynthetic systems based on material-cell hybrids and microbial photo-electrolysis cells (MPECs). Improved TiO₂/Chlorophyll composite that annealed at 400 °C was selected as electron donator to replenish additional electrons to Nostoc commune Vauch microalgae cell for N₂ fixation. Ubiquinone-0 (2,3-dimethoxy-5-methyl-1,4-benzoquinone, Q₀) was selected as electron relay that guarantees efficient transmission of electrons from abiotic material to microalgae cells. Determined by an ammonia assay kit, at constant concentration of microalgae, the constructed material-cell hybrid system photosynthetically synthesized 40.67 μM/h ammonia, while H-shape MPECs synthesized 132.70 μM/h, 19.23 times higher than that produced by pure microalgae. Using ¹⁵N₂ as the reduction gas, the constructed H-shape MPECs photosynthetically synthesized 28.37 μM/h ¹⁵NH₄⁺, 2.80 time higher than that of the MPECs without Q₀ as electron relay.Significant process has been made on the development of semi-artificial photosynthesis catering to the production of H₂– and CO₂– derived value-added products. But there are little reports on the application of semi-artificial photosynthetic system to nitrogen fixation areas. In this study we report the successful and highly efficient N₂ fixation in one step at room temperature and ambient pressure by constructing new semi-artificial photosynthetic systems based on material-cell hybrids and microbial photo-electrolysis cells (MPECs). Improved TiO₂/Chlorophyll composite that annealed at 400 °C was selected as electron donator to replenish additional electrons to Nostoc commune Vauch microalgae cell for N₂ fixation. Ubiquinone-0 (2,3-dimethoxy-5-methyl-1,4-benzoquinone, Q₀) was selected as electron relay that guarantees efficient transmission of electrons from abiotic material to microalgae cells. Determined by an ammonia assay kit, at constant concentration of microalgae, the constructed material-cell hybrid system photosynthetically synthesized 40.67 μM/h ammonia, while H-shape MPECs synthesized 132.70 μM/h, 19.23 times higher than that produced by pure microalgae. Using ¹⁵N₂ as the reduction gas, the constructed H-shape MPECs photosynthetically synthesized 28.37 μM/h ¹⁵NH₄⁺, 2.80 time higher than that of the MPECs without Q₀ as electron relay.

 https://doi.org/10.3390/polym15204099

Eco-friendly polymer composites in the form of granules based on biodegradable polycaprolactone (PCL) with the inclusion of montmorillonite (MMT) from 5 to 50 wt% were prepared by solution-casting and melt extrusion. The physicochemical properties of the composite granules were studied using FTIR spectroscopy, XRDA, DSC, and TGA methods. The paper presents comparative values of crystallinity of composite granules which depend on the method of measuring (XRDA, DSC). It was shown that the crystallinity of PCL/MMT granules was affected by the preparation method and by the MMT content, and that with increase in MMT content, crystallinity increased by up to 61–67%. The change in crystallinity of the granules also affected its biodegradation in soil. At the end of exposure in soil, the mass loss for the granules prepared by solution-casting was more than 90%, whereas for the composite granules prepared by extrusion it was less than 60%. Applying melt extrusion enabled obtaining intercalated composites with predictable features, whereas only mixed-structure microcomposites could be prepared by solution-casting.

https://doi.org/10.1039/D3CP02921B

We have reported the density functional theory investigations on the monolayered, 2 layered and bulk MoSi₂N₄ in three structural modifications called α1 [Y.-L. Hong, et al., Chemical Vapor Deposition of Layered Two-Dimensional MoSi₂N₄ Materials, Science, 2020, 369(6504), 670–674, DOI: 10.1126/science.abb7023], α2 and α3 [Y. Yin, Q. Gong, M. Yi and W. Guo, Emerging Versatile Two-Dimensional MoSi₂N₄ Family, Adv. Funct. Mater., 2023, 2214050, DOI: 10.1002/adfm.202214050]. We showed that in the case of monolayers the difference in total energies is less than 0.1 eV between α1 and α3 phases, and less than 0.2 eV between α1 and α2 geometries. The most energetically favorable layer stacking for the bulk structures of each phase was investigated. All considered modifications are dynamically stable from a single layer to a bulk structure in energetically favorable stacking. Raman spectra for the monolayered, 2 layered and bulk structures were simulated and the vibrational analysis was performed. The main difference in the obtained spectra is associated with the position of the strongest band which depends on the Mo–N bond length. According to the obtained data, we can conclude that the Raman line at 348 cm⁻¹ in the experimental spectra of MoSi₂N₄ can have more complex explanation than just Γ-point Raman-active vibration as was discussed before in [Y.-L. Hong, et al., Chemical Vapor Deposition of Layered Two-Dimensional MoSi₂N₄ Materials, Science, 2020, 369(6504), 670–674, DOI: 10.1126/science.abb7023].

https://doi.org/10.3103/S1062873823703549

It is shown that features of light propagation in plant leaves depend on the long-range ordering in chloroplasts and spectral characteristics of pigments. It is established that, allowing for the dispersion of chlorophyll’s absorption spectrum, the photonic density of states grows and the spectral peak shifts to the efficient photosynthesis wavelength range, enhancing the probability of photosynthesis.

https://doi.org/10.1021/acs.chemmater.3c01980

Exploring oxide-based red-emitting phosphors is essential for improving the color rendering index (R_a) and reducing the correlated color temperature (CCT) of white-light-emitting diode (LED) lighting sources. Especially, it is challenging to design Eu²⁺ red emission in inorganic solids. Here, the Eu²⁺-activated oxide phosphor Sr₂LaGaO₅:Eu²⁺ was synthesized with red emission peaking at 618 nm under 450 nm excitation. The crystal structure and spectral analysis indicate that Eu²⁺ tends to occupy [Sr1/LaO₈] polyhedrons with a smaller coordination number, resulting in a large crystal field splitting at the 5d level and realizing the broadband 4f–5d red emission. When Sr is substituted by Ba atoms, density functional theory calculations verify that Ba tends to enter [Sr2O₁₀] with a large coordination number, further giving rise to the lattice distortion and a giant spectral redshift (618–800 nm). The white LED device fabricated by mixing red Sr_1.8Ba_0.2GaO₅:Eu²⁺ and green Lu₃Al₅O₁₂:Ce³⁺ phosphors exhibits a high color rendering index (R_a = 92.1) and a low color-dependent temperature (CCT = 4570 K). This study will give guidance for exploring new Eu²⁺ activated oxide-based red phosphors as well as achieving tunable emission through cations’ substitution.

DOI 10.1088/1361-648X/ad0351

We propose a simple, yet feasible, model for quantum transport of fermionic carriers across tight-binding chain connecting two reservoirs maintained at arbitrary temperatures and chemical potentials. The model allows for elementary derivation of the master equation for the reduced single particle density matrix in a closed form in both Markov and Born approximations. In the Markov approximation the master equation is solved analytically, whereas in the Born approximation the problem is reduced to an algebraic equation for the single particle density matrix in the Redfield form. The non-Markovian equation is shown to lead to resonant transport similar to Landauer's conductance. It is shown that in the deep non-Markovian regime the transport current can be matched with that obtained by the non-equilibrium Green's function method

 Journal of Siberian Federal University: Chemistry, 16(3), pp. 447-458.

A study of the colloidal stability of nanosuspensions obtained by diluting concentrated silicasols was carried out. A wide range of mass concentrations of nanoparticles (from 1 to 50 wt.%) and average sizes of primary particles (from 10 to 35 nm) were considered. The analysis of sedimentation experiments showed that the considered samples have a very high colloidal stability. The characterization of the nanoparticle sizes by electron microscopy was carried out. The particle size distributions in the suspension were obtained by acoustic spectroscopy. Almost all of the considered silica sols have been shown to have a very narrow particle size distribution. The dependences of the dynamic viscosity of nanosuspensions on the concentration and size of nanoparticles are obtained. Based on the dependences, empirical correlations in a wide range of particle concentrations were obtained.

https://doi.org/10.1007/s11182-023-02996-z

The paper studies parameters of the snow-ice cover and forest ground determined by the integrated approach based on the global navigation satellite system reflectometry. Experimental data on the amplitude and time response of satellite navigation signals are processed by fast Fourier transform and then analyzed using mathematical methods based on the multipath echoes model in terms of geometrical optics. Using a combination of reflectometry and numerical simulation of the surface layers based on local weather data, it is possible to evaluate not only the current state of these layers, but also predict their dynamic development.

https://doi.org/10.1134/S0021364023602555

A spin-crossover mechanism in ludwigite Со₃BO₅ is proposed on the basis of the DFT calculation with SCAN potentials. The role of separate exchange interactions in the establishment of the long-range magnetic order is demonstrated within the Monte Carlo method.

https://doi.org/10.1134/S0021364023602336

The dependence of the topology of the fermion excitation spectrum on the magnetic state of the system is analyzed taking into account the structure of the Te–Mn–Te trilayer in the Te–Bi–Te–Mn–Te–Bi–Te layer sequence of the MnBi₂Te₄ van der Waals single crystal, crystal field effects, spin–orbit coupling, and the covalent mixing of electronic states of Mn²⁺ ions with electronic states of Te^2– ions in the strong electron correlation regime. The Chern number in the ferromagnetic phase, which is due to the kinematic interaction between Hubbard fermions, is equal to 1; i.e., the topology of the band structure of the Te–Mn–Te trilayer is nontrivial. The Chern number in the paramagnetic phase is zero; i.e., the topology is trivial. The magnetic moments of Mn²⁺ ions for the constructed spin orbitals are perpendicular to the layers. The magnetic moments of Mn²⁺ ions in the nearest layers are antiferromagnetically ordered via the Anderson mechanism.

A study of the colloidal stability of nanosuspensions obtained by diluting concentrated silicasols was carried out. A wide range of mass concentrations of nanoparticles (from 1 to 50 wt.%) and average sizes of primary particles (from 10 to 35 nm) were considered. The analysis of sedimentation experiments showed that the considered samples have a very high colloidal stability. The characterization of the nanoparticle sizes by electron microscopy was carried out. The particle size distributions in the suspension were obtained by acoustic spectroscopy. Almost all of the considered silica sols have been shown to have a very narrow particle size distribution. The dependences of the dynamic viscosity of nanosuspensions on the concentration and size of nanoparticles are obtained. Based on the dependences, empirical correlations in a wide range of particle concentrations were obtained.

https://doi.org/10.3103/S1062873823703343

(Mg/ZrO₂)₅₂ multilayer nanostructures with different thicknesses of Mg layers and the same thickness of ZrO₂ layers are obtained via the ion-beam sputtering of two targets in an argon medium. The thickness of one bilayer (Mg + ZrO₂) varies from 3.6 to 8.5 nm. It is found that using zirconium dioxide prevents the oxidation of the magnesium phase. An electric percolation threshold is observed when the morphology of magnesium layers changes (a transition from discrete to continuous morphology) as a result of an increase in the bilayer thickness. A change of the electrotransport mechanism is identified in the (Mg/ZrO₂)₅₂ multilayer nanostructures upon passing through the percolation threshold.

https://doi.org/10.1016/j.mtcomm.2023.107191

The effects of exciton Bose condensation in strongly correlated spin crossover systems are considered within the effective Hamiltonian obtained from the two-orbital Hubbard–Kanamori model. The spectrum of collective excitations at various points of the temperature-crystal field phase diagram is calculated. The role of the electron–phonon interaction is discussed. A novel mechanism of excitonic and related magnetic order photoenhancement in strongly correlated spin crossover systems based on the massive collective phase mode appearance is demonstrated. In addition, we have shown that exciton and associated with it magnetic ordering can be photoinduced outside the exciton condensate phase due to the gap presence in the spectrum of single excitations.

DOI: 10.1109/LAWP.2023.3278333

In this letter, the possibility of synthesizing ultra-wideband (UWB) impulses with a conventional log-periodic dipole antenna (LPDA) mounted on a quadrotor unmanned aerial vehicle (UAV) was demonstrated. The formation of impulses using LPDA (bandwidth from 427 MHz to 1.01 GHz) with duration of 1.9 ns, containing one period of field oscillations, became possible due to compensation of amplitude and phase-frequency distortions introduced by the antenna into radiated and received impulses. Compensation for these distortions was carried out by the inverse filtering method after calibrating the antenna-feeder path at various heights with the UAV hovering above the reference reflector (brass mesh). The conductive carbon elements of the UAV, located in the near field of the antenna, are indirectly taken into account during the calibration of antenna-feeder path parameters and do not introduce significant distortions into the generated impulses. The suggested method of synthesizing UWB impulses can find application in environmental remote sensing and can also be used to sharpen the fronts of impulses radiated\received with LPDA.

https://doi.org/10.1016/j.optlaseng.2023.107797

We consider a waveguide with a symmetrically integrated silicon cylinder. This design supports a symmetry protected bound state in the continuum (BIC) with Q-factor controlled by slight displacement of the cylinder. When excited by a TE₁₀ electromagnetic wave, the BIC leads to giant optical forces near the cylinder. These forces have a strong impact on nanoparticles being dragged by liquid flow over the waveguide as they approach the cylinder. At the same time, the nanoparticles perturb the resonant frequency of the BIC with a value proportional to their volume and proximity to the cylinder. Therefore, the interplay between the resonant width of the BIC and the nanoparticle frequency perturbation determines the positions of the nanoparticles trapped around the cylinder. This paradigm demonstrates resonant self-trapping and sorting of nanoparticles by size through BIC excitation. We highlight the extreme sensitivity of these effects to the frequency of the injected TE wave. Additionally, we show that these results remain valid when considering the finite conductivity of metal