bluuebunny/crossref_metadata_2025 huggingface dataset:
Contribution of vibrational states of diatomic impurity molecules to the low-temperature heat capacity of a crystal
Authors: Salamatov E. I.
Published: January 2025

The dynamics of nonmagnetic linear impurity molecules in the crystal matrix are investigated theoretically by using a simple model connecting the tunnel states associated with rotation of a molecule with vibrations of its center of mass. The interaction between randomly located impurity molecules leads to a concentration dependence of the distribution function for low-energy excitations responsible for anomalous behavior of the heat capacity of such defective crystals at low temperatures. The obtained results are in qualitative agreement with experimental data.
On stable two-dimensional solitons and nonhomogeneous states in magnets without inversion centers
Authors: Zhmudskiĭ A. A. , Ivanov B. A.
Published: January 2025

Two-dimensional localized magnetic solitons in magnets without inversion centers are considered taking into account anisotropy in the basal plane. It is shown that static solitons in such magnets are stable according to Lyapunov’s criterion. The mechanism of soliton stabilization is connected with the presence of invariant linear in gradients in the equation for the energy of the magnet. The properties of such solitons change radically when an infinitely small anisotropy in the basal plane is taken into account. The soliton energy in the models of purely axial magnet considered earlier can be infinitely low, while in the case of a finite anisotropy of this type the energy has a finite value in the entire thermodynamic stability region of the homogeneous ground state.
Mössbauer studies of CoGa2−xFexO4 (x= 0.8,1)
Authors: Sultanov G. D. , Seidov Z. Yu. , Kaplienko A. I.
Published: January 2025

The results of Mössbauer studies of dilute spinels CoGa2−xFexO4 (x = 0.8,1) in the temperature range 5−330 K are presented. The relaxation nature of the Mössbauer spectra indicates the presence of spin fluctuations over a wide temperature range.
Resonant reflection of light by a heterostructure with a single quantum well
Authors: Kosobutskiĭ P. S.
Published: January 2025

A theoretical analysis is carried out of the conditions for formation of extrema of the exciton reflection of light from a heterostructure with a single quantum well. An expression is obtained connecting the parameters of the quantum well and of the confining layer.
On the possibility of observation of the Aharonov–Bohm effect in transport measurements in a charge-density-wave conductor
Authors: Rozhavsky A. S.
Published: January 2025

We have studied the conditions for the observation of the Aharonov–Bohm oscillatory magnetic flux-dependent component in the transport charge-density-wave (CDW) current in a thin film with columnar defects placed in a strong magnetic field. The flux through an isolated defect exceeds the magnetic flux quantum Φ0; the defect serves as a solenoid. We predict the percolation and instanton contributions to the oscillatory CDW current. It has been shown that even at moderate temperatures the amplitude of the ABE produced oscillatory current and may reach an order of 10−4 of the transport current at high enough concentration of columnar defects. The period of the oscillations over the magnetic flux is Φ0/2.
Critical parameters of high-temperature HgBaCaCuO ceramics with T
c= 133 K: effects of magnetic field and pressure
Authors: Tarenkov V. Yu. , Abaleshev A. V. , D’yachenko A. I. , Lutsiv R. V. , Myasoedov Yu. N.
Published: January 2025

The dependence of superconducting transition temperature Tc and critical current density Jc on hydrostatic pressure up to 10 kbar is investigated for Hg0.8Pb0.2Ba2Ca2Cu308+δ (Hgl223) ceramic samples with Tc= 133±0.5 K. The rate of variation dTc/dP is 0.28±0.04 K/kbar for pressures up to 3 kbar and decreases to 0.18±0.04 K/kbar for P ≈ 10 kbar. The nonlinearity of dTc/dP is apparently explained by a change in the hole concentration in CuO2 planes under pressure. The observed strong response of critical current to pressure (d ln(Jc)/dP=0.2±0.02 kbar−1) indicates weak coupling in the current-carrying cluster of the ceramics.
Indications of angstrom thickness of isolated high-temperature superconducting layers
Authors: Mikheenko P. N.
Published: January 2025

The effective thickness of YBa2Cu3Ox superconducting layers is estimated. The anomalously large difference between the mean-field critical temperature and the Berezinskii–Kosterlitz–Thouless (BKT) transition temperature in single-layered films, Y/Pr superlattices, and polycrystalline samples with broken CuO2 planes is explained. The dynamics of the temperature of the BKT transition involving a change in the number of piled YBa2Cu3Ox unit cells is traced. A formula connecting the BKT transition temperature for HTS materials with the resistance of samples per square area element is derived.
Critical currents and relaxation in Josephson media
Authors: D’yachenko A. I. , Stankowski J.
Published: January 2025

The main aim of this paper is to show that Josephson critical current Ic stability to high magnetic fields H≫Hc1 tends to hysteretic relaxation rate of the Josephson media critical current Jc(t) and produces a change in the Ferrell–Prange equation. In the framework of the discussed model, the reason for Jc(t) vs. H hysteresis lies in the irreversible dependence of the granule surface current. It is shown that the effective intergranular field Hg in Josephson media plays a secondary role at these fields.
Resistive behavior of layered superconductors with Josephson coupling
Authors: Artemov A. N. , Martynovich A. Yu.
Published: January 2025

A theory of phase transition in layered superconductors is constructed in the mean-field approximation. In zero magnetic field, it occurs as a first-order transition and is due to instability in the excitation spectrum resulting in collective excitations. The effect of transport current on the form of the transition is investigated. Small currents reduce the stability region of the metastable state. In the case of strong currents, metastable states are not observed, and the rearrangement of the excitation spectrum occurs as a second-order phase transition. The rearrangement affects the concentration of free vortices determining the resistive properties of the superconductor. Weak interaction of screened vortices in a dipole leads to a current dependence of the free vortex concentration above the phase-transition temperature. This is manifested in a broadening of the universal jump in the temperature dependence of the IVC exponent.
Fractal properties of critical current of a self-similar system of Josephson junctions connected in parallel
Authors: Grib A. N.
Published: January 2025

A fractal value (the local cell dimension Dc) has been found to characterize the dependence of the maximum Josephson current square I2 on the magnetic field in self-similar systems of Josephson junctions connected in parallel and separated by distances distributed like Cantor set of segments. The cell dimension has been shown to be related to the fractal system dimension D by the relationship Dc≈2 − D, which had been checked for systems with the different fractal dimensions.
Current–phase dependences of superconducting superlattices
Authors: Gogadze G. A. , Omel’yanchuk A. N.
Published: January 2025

A system of equations derived on the basis of the Ginzburg–Landau theory is used for calculating the current–phase dependence for superconducting superlattices (SS). The crossover from the Josephson-like behavior of SS (high values of the constant λ characterizing the suppression of the order parameter) to a quasi-one-dimensional flow of superconducting current is investigated. It is shown that with decreasing λ, the peak of the superconducting current of the SS is displaced towards lower values of the phase difference over a lattice period.
Emergence of superconductivity in two-dimensional Be films
Authors: Semenenko E. E. , Tutov V. I.
Published: January 2025

The existence of the threshold value of resistance Rq=h/4e2 = 6.45 kΩ (resistance quantum) corresponding to the emergence of superconductivity in two-dimensional Be films is investigated. The Tc(R□) dependence for cold-deposited Be films is analyzed. The value of R□ was varied for the first time by the following three methods: by changing the thickness of quench-condensed films, by step annealing in a 10−10 Pa vacuum, and by annealing in a 10−3 Pa vacuum at 300 K. The values of Tc for films having the same value of R□, but obtained by different methods differ significantly. The behavior of the Tc(R□) curve of quench-condensed films indicates the possibility of existence of a threshold value of R□=Rq for homogeneous two-dimensional films. In the case of heterogeneous films, superconductivity also emerges for R□>Rq. Such conditions are probably valid for films made of other materials.
Manifestation of the phonon drag of vortices on measuring HTSC fluctuation thermopower
Authors: Chiang Yu. N. , Shevchenko O. G.
Published: January 2025

Comparative investigations and analysis of the temperature-dependent thermopower and resistivity of HTSC monocrystals are carried out in the temperature interval where superconducting fluctuations are dominant. It is shown that, at the temperatures below mean-field Tc, nonisothermality of thermopower measuring conditions could be responsible for phonon drag of dissociated vortex-antivortex pairs capable of being thermally excited in quasi-two-dimensional systems to which HTSC materials belong.
Peculiarities in the behavior of thermal conductivity, thermal diffusivity, and specific heat of high-temperature superconductors near T
c
Authors: Kamilov I. K. , Batdalov A. B. , Abdulvagidov Sh. B.
Published: January 2025

The thermal conductivity of the same YBa2Cu3O7−δ single crystal is measured for the first time both in the ab plane (κab), and in the direction of the c-axis of the crystal (κc) in the temperature range 4–300 K. No anomalies typical of high-Tc superconductors near Tc and below due to the electron–phonon interaction are observed in the κc(T) dependence. Anomalies are observed in the thermal conductivity of Ag-doped yttrium ceramics near Tc and attributed to the effect of superconducting fluctuations.
Acoustic plasmons and anomalous thermal conductivity of high-temperature superconductors
Authors: Pashitskiĭ È. A. , Pentegov V. I.
Published: January 2025

It is shown that anomalies in the temperature dependence of thermal conductivity κ(T) for high-temperature superconductors below the critical temperature can be due to the presence in the gap 2Δ of weakly attenuating collective electron excitations of the Bose type with the acoustic energy-momentum relation (acoustic plasmons). Such a “plasmon” mechanism of thermal conductivity makes it possible to explain the κ(T) peak in the plane of CuO2 layers below Tc, the quadratic dependence κ(T) ∼ T2 in the region T≪Tc, suppression of the κ(T) peak by nonisovalent impurities, and inversion of anisotropy in κ(T) in the plane of the layers in YBa2Cu3O7 crystals upon a transition from the normal to the superconducting state.
Influence of anisotropy of a superconductor on electromagnetic wave reflection
Authors: Yampol’skiĭ S. V.
Published: January 2025

The reflection of electromagnetic waves (EMW) at the surface of an anisotropic superconductor is investigated. Parameters of the reflected wave are expressed in terms the components of the surface impedance tensor. It is shown that anisotropy of the superconductor leads to two effects. First, a linearly polarized wave has in general an elliptic polarization after reflection. Second, the polarization ellipse of the reflected wave is turned relative to the EMW plane of incidence. The strength of these effects is determined by the ratio of the London penetration depth λ to the incident EMW length λw. It is found that the effect of anisotropy in the microwave region (λ/λw≪1) is virtually absent. The observed effects become noticeable only in the optical range (λ/λw≃1). In the case when the polarization plane of the incident EMW is parallel to the anisotropy axis, the polarization of the reflected EMW remains unchanged.
Paramagnetic Meissner effect in the mixed state of Y–Ba–Cu–O ceramics
Authors: Bukhon’ko F. N.
Published: January 2025

The behavior of the microwave impedance of Y–Ba–Cu–O ceramic samples in a narrow temperature range < 1 K near the superconducting transition temperature correlates with the usual mechanism of superconductivity in HTS ceramics in an external magnetic field. A further decrease in temperature causes a sharp increase in the reactive impedance component instead of its expected decrease, which can be explained by the emergence of an additional positive contribution to the microwave magnetic susceptibility of the sample owing to spontaneous orbital moments. The value of the positive contribution is inversely proportional to the intensity of magnetic component of the microwave field in the resonator. As the sample goes over to the paramagnetic state below 90 K, the impedance X(T) acquires temperature oscillations associated with the quantization of the magnetic flux Φ(T) penetrating the network of Josephson junctions. It is assumed that the microwave magnetic flux penetrates a superconducting sample below 90 K in the form of hypervortices.
“Symmetry-dependent” incommensurate magnetic phases in magnetodielectrics
Authors: Bar’yakhtar V. G. , Stefanovskiĭ E. P.
Published: January 2025

The modem phenomenological theory of modulated long-periodic phases in magnetically ordered crystals is analyzed. The main attention is paid to incommensurate magnetic phases existing due to the presence of invariants in the free energy of the magnet, which are linear in the first spatial derivatives of components of spin density moments. Equilibrium magnetic configurations of some specific objects are considered.
Skin effect in polycrystals
Authors: Kaganova I. M. , Kaganov M. I.
Published: January 2025

The effective impedance of a polycrystalline metal under the conditions of the anomalous skin effect is calculated in the case when the average size of a crystallite is larger than the mean free path of conduction electrons under the assumption of a weak anisotropy of the conductivity tensor of the single crystal whose grains form the polycrystal. The calculations are made in the perturbation theory by using the Fourier method, which makes it possible to avoid the calculation of random fields in the r-representation. The Fourier method is used to reproduce the expressions of the effective impedance of the polycrystalline metal obtained earlier under the conditions of the normal skin effect. The proposed algorithm of calculations makes it possible to calculate the effective impedance of polycrystals for a wide class of metals in a large range of parameters. The numerical estimate of effective impedance under the conditions of anomalous skin effect is obtained for a simple model of quadratic energy–momentum relation for conduction electrons of the initial single crystal.
Scattering mechanism electron–phonon–surface and its contribution to low-temperature resistance of metals
Authors: Startsev V. E. , Ustinov V. V. , Dyakina V. P.
Published: January 2025

The resistivity of high-purity tungsten single crystals is studied as a function of their transverse dimensions and the crystallographic orientation of facetting planes in the temperature range 2–40 K under the conditions of the size effect. The dependences of the resistance of thin wires on temperature and thickness are calculated under the conditions of small-angle electron–phonon scattering in the model taking into account the dependence of the probability of electron scattering at the surface on the grazing angle. It is proved both theoretically and experimentally that the observed nearly quadratic temperature dependence of resistivity is mainly due to the interference between electron–phonon and electron–surface scattering.
Effect of electron viscosity and impurities on quantum motion of dislocations through Peierls barriers
Authors: Natsik V. D. , Kirichenko G. I. , Pustovalov V. V. , Soldatov V. P. , Shumilin S. È.
Published: January 2025

Temperature dependences of the yield stress and the strain rate sensitivity of deforming stress are studied experimentally for a slip system (100)⟨010⟩ in pure single crystals β-Sn in the temperature range 0.5–4.4K. The existence of the low-temperature anomaly observed earlier and having characteristic features of a quantum process (a transition from thermally activated to athermal plastic flow in the temperature range near and below 1 K) is confirmed. It is shown that a superconducting transition in the samples extends significantly the temperature range in which the anomaly is observed. The effect of doping of Sn with Cd on the anomaly is investigated. It is found that a low impurity concentration increases the threshold temperature of the anomaly, while a high concentration leads to disappearance of athermal plastic flow. A detailed theoretical analysis of experimental observations is carried out on the basis of the dominating effect of Peierls barriers on the mobility of dislocations in the given slip system (which has been established earlier) and by using the theoretical data on quantum motion of dislocations in the Peierls relief. Simple analytic expressions are obtained for temperature dependences of plasticity parameters in the region of quantum anomaly. The theoretical and experimental results are compared quantitatively. The procedure of calculation of empirical values of fundamental parameters in the dislocation theory (Peierls stress, effective mass, linear tension, and the electron friction coefficient for a dislocation string) is developed and applied to the slip system.
On the temperature dependence of the order parameter in a superconductor
Authors: Antsygina T. N. , Slyusarev V. A.
Published: January 2025

The reasons behind the striking coincidence of the temperature dependence of the order parameter in the microscopic theory of superconductivity and the behavior of the magnetization of a Weiss magnet are discussed.
Electron-structure relaxation of YBaCuO films in the normal and superconducting states
Authors: Samovarov V. N. , Libin M. Yu. , Fugol I. Ya.
Published: January 2025

The time dependence of absorption coefficient in metallic YBa2Cu3O6+x films associated with electron-structure relaxation of films after their rapid cooling to low temperatures is studied by the optical spectroscopy method. It is shown that the long-time relaxation in the superconducting phase is frozen, but the short-time relaxation component connected with electrons states near the Fermi surface is left.
Optical response to superconducting transition in IR reflection and transmission of Y–Ba–Cu–O
Authors: Svishchev V. N. , Fugol I. Ya.
Published: January 2025

The reflection and transmission spectra of Y–Ba–Cu–O thin films with a moderate oxygen doping are measured in the near infrared range 2500–10000 cm−1 at temperatures varying from 300 and 10 K. It is found that the optical response to the superconducting transition is determined by the temperature equilibrium state and the conditions of thermal cycling of the samples. The reflection and transmission spectra have different sensitivities to Y–Ba–Cu–O structures below and above the critical temperature T* separating the states with different degrees of localization of charge carriers. It is shown that the two contributions to the IR spectral functions come from different groups of charge carriers forming the superconducting condensate.
Magnetic and high-frequency properties of texturized YBaCuO samples in a magnetic field up to 12 T
Authors: Chabanenko V. V. , Szymczak H. , Piechota S.
Published: January 2025

The results of analysis of irreversible phenomena in magnetization, magnetostriction, and high-frequency absorption of texturized YBa2Cu3O7–δ superconductors (123 phase) are considered. The magnetization M exhibits a reversible “training” effect in contrast to LTS materials in which this effect is irreversible. The results of analysis of anisotropy in the hysteresis of giant magnetostriction, in which magnetic flux instability is manifested, are discussed. The magnetolamination is discovered and its mechanism is considered. A “normal” hysteresis observed in electromagnetic field absorption differs from an “anomalous” hysteresis typical of granular weakly connected HTS medium.
Magnetic properties of the Hubbard model with strong repulsion
Authors: Zaitsev R. O.
Published: January 2025

The magnetic properties of copper oxides are studied taking into account the spin and orbital splitting of copper cations and oxygen anions. The strong electron-electron Coulomb repulsion leads to the emergence of concentration and temperature dependences of magnetic susceptibility.
Anisotropy of spin reorientation fields in Nd2CuO4
Authors: Ignatova T. V. , Gaiduk A. L. , Kolobov I. G. , Fil’ V. D. , Fil’ D. V. , Barilo S. N. , Zhigunov D. I.
Published: January 2025

The anisotropy of fields of spin reorientational phase transitions in Nd2CuO4 is studied at helium temperatures by using data on magnetoelastic properties. The ratio of parameters of the model four-sublattice Hamiltonian describing the observed anisotropy at T > 1.5 K is estimated. The peculiarities of the elastic moduli observed at lower temperatures also display a marked anisotropy, but their explanation requires an explicit consideration of the rare-earth spin structure.
Effect of axial tension on antiferromagnetic transformation in europium
Authors: Dikovsky V. Ya. , Amitin E. B. , Kovalevskaya Yu. A. , Beloshapko A. G.
Published: January 2025

An anomaly in the electrical resistance of a Eu sample near the Néel point is studied under a tensile stress σ = 0.25–0.5 kbar, sufficient to decrease the order parameter from 12 to 4. It is shown that the antiferromagnetic transformation in the “four-component” state remains a first-order transition in accordance with theoretical concepts. Apart from the first-order transition domain, a wide temperature region exists, in which the behavior of the derivative of the resistance is described by a power function of reduced temperature. In this region, the stable value of the critical index λ = 0.5±0.05, which has been determined for the undeformed sample, can be explained by the influence of the Gaussian tricritical point. As the sample goes over to the “four-component” state, the critical index decreases to λ = 0.2–0.3.
Influence of defect structure on magnetic and electronic properties of Hg1–xCrxSe and Hg1–xCoxSe
Authors: Prozorovskiĭ V. D. , Reshidova I. Yu. , Puzynya A. I. , Paranchich Yu. S.
Published: January 2025

The results of experimental investigations of Shubnikov-de Haas oscillations on the microwave frequencies, electron spin resonance, magnetic susceptibility, relaxation dielectric losses are considered as well as the results of galvanomagnetic measurements on Hg1–xCrxSe and Hg1–xCoxSe monocrystalline samples. An analysis of the results shows that magnetic and electronic properties of Hg1–xCrxSe and Hg1–xCoxSe are determined by the defect structure of the material and by the defects forming this structure. The defect structure also determined the manifestation of critical phenomena in Hg1–xCrxSe.
Elastic and relaxation properties of HTS composites BSCCO(2223)+(0–100)% Ag in the temperature range 5–300 K
Authors: Pal-Val P. P. , Pal-Val L. N. , Natsik V. D. , Kislyak I. F. , Dotsenko V. I.
Published: January 2025

Acoustic and superconducting properties of ceramic composites Bi1.6Pb0.4Sr2Ca2Cu3O10+δ–Ag are investigated for silver concentrations varying over a wide interval (0–100%). The height of the absorption peak observed near 150 K in the temperature spectrum of ultrasound absorption in samples of pure ceramics BSCCO(2223) varies nonmonotonically upon the introduction of silver in the ceramics. The relaxation origin of the peak has been established and the activation parameters of the corresponding relaxation process localized at the ceramic grain boundaries have been determined. The intensity of another relaxation peak observed in composite samples BSCCO(2223)–Ag at 70 K increases with Ag concentration. The correlation observed between anomalies on the concentration dependences of acoustic properties and the superconducting transition width indicates that the introduction of silver into intergranular space determines to a considerable extent the elastic and relaxation properties of the composites under investigation as well as their superconducting properties.
Inertial effects in plasticity of α-titanium at low temperatures down to 0.5 K
Authors: Moskalenko V. A. , Kovaleva V. N. , Natsik V. D. , Pustovalov V. V. , Shumilin S. È.
Published: January 2025

Temperature dependences of the yield stress, strain-rate sensitivity, and activation volume of α-titanium samples with various concentrations of oxygen impurity atoms (0.06–0.96 at.%) are studied in detail. The presence of low-temperature anomalies in these parameters is confirmed. The empirical values of the theoretical parameters of low-temperature plasticity of Ti–O interstitial solid solutions under investigation are determined by using the rigorous procedure of thermal-activation analysis of experimental data proposed earlier. The emergence of the anomaly is associated with a change of the thermally activated mechanism of overcoming of impurity barriers for a thermoinertial mechanism, which takes place in the vicinity of the threshold temperature Ti depending on the oxygen concentration. An analysis of the dependence of Ti on the impurity concentration leads to a simple empirical formula for the temperature dependence of the dynamic drag coefficient for dislocations in the low-temperature region.
Contribution of the interaction of identical particles to the diffusion of classical and quantum mixtures
Authors: Adamenko I. N. , Zhukov A. V. , Nemchenko K. È.
Published: January 2025

An exact expression is obtained for the diffusion coefficient of a two-component gas with an arbitrary dispersion relation and statistics. Various limiting cases are considered. The limits of variation of the diffusion coefficients are found. It is shown that in many cases the diffusion coefficient may depend considerably on the rate of relaxation between particles of the same type. The roton–impuriton system of superfluid helium isotope mixture is considered by way of an example.
Metastable localized solitons in two-dimensional antiferromagnets: dynamics and contribution to response functions
Authors: Ivanov B. A. , Kolezhuk A. K. , Filin D. V.
Published: January 2025

The dynamics of internal degrees of freedom of localized topological solitons (vortices) in 2D easy-axis antiferromagnets in an external magnetic field is studied, and the contributions to the response functions is calculated. These solitons are dynamically stable to collapse due to the conservation of the vortex momentum.
Synthesizing spin–orbit couplings and symmetry-protected topological phase in acoustic metamaterials
Authors: Wang Gang , Wang Xu Feng , Fan Chun Zhen
Published: January 2025

Spin–orbit couplings (SOCs) underlie several key concepts of topological matter. However, acoustic waves lack intrinsic spin and SOCs, which makes some topological phases impossible. We develop in the present work a realistic scheme to synthesize simultaneously the intrinsic and Rashba–Dresselhaus SOCs in acoustic systems and explore the symmetry-protected topological phase induced by the SOCs. To be precise, we construct a two-leg ladder composed of acoustic resonators and linking tubes. Utilizing the concept of pseudospin, the spin-1/2 is encoded by the leg degree of freedom of the ladder, and meanwhile, the SOCs are achieved by engineering the couplings between resonators. We further highlight the emergence of the symmetry-protected topological phase respecting the chiral unitary (AIII) symmetry in such acoustic SOC lattices. This scheme is confirmed by the full-wave simulations. Our acoustic structure is within immediate experimental reach and enables the direct visualization of symmetry-protected topological boundary states, not yet been observed experimentally. Our results represent a route to synthesize the SOCs and will benefit an in-depth study of the spin–orbit physics in acoustics.
Nanoscale insights on phase transition dynamics of doped VO2 for memristor devices
Authors: Wang Lin , Chen Li , Xu Xionghu , Hou Zhangchen , Li Yafang , Shang Liyan , Zhang Jinzhong , Zhu Liangqing , Li Yawei , Cao Fei , Wang Genshui , Chu Junhao , Hu Zhigao
Published: January 2025

This study utilized co-sputtering to fabricate Mo-doped VO2 films and identified an optimal concentration exhibiting a lower phase transition temperature (Th = 55.8 °C) and a broader hysteresis window (Δ T = 13.6 °C). At the atomistic scale, it is demonstrated that Mo dopant-induced localized strain accelerates the phase transition, which leads to the relaxation of the tetragonal structure. Furthermore, the effects of Mo doping on the phase transition process and electrical properties are characterized at the nanoscale using conductive atomic force microscopy and Kelvin probe force microscopy, and the potential application in selectors can be evaluated. The results indicated that Mo doping destabilizes the M1 phase by introducing a high density of electrons, thereby significantly reducing the electron–electron interactions as per the Mott model. Moreover, the device exhibited stable threshold and memristive properties at room temperature, quickly switching from high to low-resistance states at a threshold voltage of 2.37 V and maintaining stability over more than 1000 cycles with a selectivity >102. The present work not only highlights the role of Mo doping in enhancing the functional properties of VO2 but also demonstrates its feasibility in high-performance selectors devices.
Enhanced size-dependent efficiency of InGaN/AlGaN near-ultraviolet micro-LEDs
Authors: Islam Abu Bashar Mohammad Hamidul , Kim Tae Kyoung , Cha Yu-Jung , Yun Joosun , Song June-O , Shin Dong-Soo , Shim Jong-In , Kwak Joon Seop
Published: January 2025

This study presents an approach for enhancing the external quantum efficiency (EQE) of multiple-quantum-well InGaN/AlGaN near-ultraviolet (NUV) micro-light-emitting diodes (micro-LEDs) without changing the epitaxial layer. Unlike the size-dependent EQE reduction observed in blue, green, and red micro-LEDs, the EQE of NUV micro-LEDs at high current densities (≥10 A/cm2) improves as the device dimensions shrink from 500 × 500 μm2 to 20 × 20 μm2. A 20 × 20 μm2 micro-LED achieves a peak EQE of 12.3%, compared to 8.60% for a larger 500 × 500 μm2 micro-LED. Experimental results attribute this EQE enhancement to improved light-extraction efficiency, driven by better current spreading. In larger micro-LEDs, pronounced current crowding causes carrier overflow from the active region, leading to reduced EQE at high current densities. These findings highlight the promising potential of NUV micro-LEDs for diverse applications.
Propagation characteristics of THz waves through magnetized dusty plasma with a ceramic substrate
Authors: Su Ruiming , Xi Baolong , Ma Jinping , Ji Lingzhao , Tu Pu , Shao Kaihua , Zhao Xi , Shi Yuren
Published: January 2025

The shift-operator finite-difference time-domain method is applied to investigate the transmission properties of terahertz (THz) waves through a fully ionized magnetized dusty plasma sheath with time-varying electron density distribution and a ceramic substrate. It is interesting and noteworthy that the inclusion of the ceramic layer induces a phenomenon whereby the transmissivity and reflectivity of THz waves exhibit a quasi-periodic variation with respect to frequency within the higher-frequency band (above 0.3 THz), which differs from previous reports. This result is also confirmed by the theoretical analysis, which shows that the oscillating-period of the transmissivity and reflectivity is inversely proportional to the thickness of the ceramic layer. Numerical simulations indicate that the left-hand circularly polarized waves penetrate the plasma model with a ceramic substrate more easily than the right-hand circularly polarized waves. Decreasing the electron density, plasma thickness, or dielectric constant of the ceramic leads to an increase in transmissivity. However, it is somewhat opposite when the external magnetic field strength decreases. Our findings maybe provide theoretical support for possible alleviating the issue of “blackout.”
Investigation of (mis-)orientation in zincblende GaN grown on micro-patterned Si(001) using electron backscatter diffraction
Authors: Waters Dale M. , Thompson Bethany , Ferenczi Gergely , Hourahine Ben , Cios Grzegorz , Winkelmann Aimo , Stark Christoph J. M. , Wetzel Christian , Trager-Cowan Carol , Bruckbauer Jochen
Published: January 2025

We present the application of electron backscatter diffraction (EBSD) as a technique for characterizing wurtzite (wz) and zincblende (zb) polytypes of GaN grown upon micropatterned Si (001) substrates. The Si substrate is etched to create parallel V-shaped grooves with opposing {111} facets before the deposition of GaN. EBSD revealed that wz-GaN growth fronts initially form on the {111} Si facets before undergoing a transition from a wurtzite to zincblende structure as the two growth fronts meet. Orientation analysis of the GaN structures revealed that the wz-GaN growth fronts had different growth orientations but shared the same crystallographic relationship with the zb-GaN such that ⊥{303¯8}wz∥⟨110⟩zb, ⟨112¯0⟩wz∥⟨110⟩zb, and ⊥{303¯4}wz∥⟨001⟩zb. Furthermore, the crystallographic relationship, {0001}wz-GaN∥{111}zb-GaN∥{111}Si, and alignment of the wz- and zb-GaN with respect to the Si substrate was investigated. The two wz-GaN ⟨0001⟩ growth directions were expected to coalesce at an angle of 109.5°; however, measurements revealed an angle of 108°. The resultant misalignment of 1.5° induces misorientation in the zb-GaN crystal lattice. While the degree of misorientation within the zb-GaN lattice is low, <1°, the zb-GaN lattice is deformed and bends toward the wz-GaN interfaces about the specimen direction parallel to the length of the V-groove. Further EBSD measurements over larger areas of the sample revealed that these results were consistent across the sample. However, it was also revealed that additional factors induce changes in the orientation of the zb-GaN lattice, which may relate to the initial growth conditions of the zb-GaN.
Observation of transient trion induced by ultrafast charge transfer in graphene/MoS2 heterostructure
Authors: Wang Chen , Chen Yu , Ma Qiushi , Suo Peng , Sun Kaiwen , Cheng Yifan , Lin Xian , Liu Weimin , Ma Guohong
Published: January 2025

Van der Waals (vdW) heterostructures constructed from transition metal dichalcogenidess provide an ideal platform for exploring various quasiparticle behaviors, with trion—composed of neutral exciton and charged carrier—being a notable example. There are typically three methods to generate trion: electrical doping, chemical doping, and direct optical doping. The first two methods generate static trion, while the last gives rise to transient trion. Here, we present an indirect optical doping approach to generate transient trion via ultrafast charge transfer (CT) and achieve control over the trion-to-exciton ratio by adjusting CT in Gr/MoS2 heterostructure. Furthermore, we demonstrated that dynamics of the transient trion generated with this method, which shows slightly longer lifetime than that of exciton accounted for the Coulomb interactions between trion and charged defect. This study provides fresh perspectives on the construction of desired quasiparticles, dynamical characterization, and the control of the many-body interaction in two-dimensional structure.
Coherent magnon transport in a van der Waals antiferromagnet
Authors: Chen Jilei , Yuan Rundong , Yu Kanglin , Wang Xiaoyu , Sheng Lutong , Wang Jinlong , Hua Chensong , Yu Weichao , Xiao Jiang , Liu Song , Yu Dapeng , Ansermet Jean-Philippe , Wang Zhe , Yu Haiming
Published: January 2025

Recently developed van der Waals magnets offer a promising platform for advancing spintronics. The weak interlayer antiferromagnetic exchange coupling in van der Waals antiferromagnets allows for unique spin dynamics and control over magnons. In this study, we present the excitation and detection of coherent magnon transport in the van der Waals antiferromagnet CrPS4. We observe pronounced coherent magnon–magnon coupling between the optical and acoustic magnon branches, resulting in hybridized magnon modes that can be tuned by modulating the coupling strength, enabling a tunability across a broad frequency range exceeding 10 GHz. The group velocity of the antiferromagnetic magnons is estimated to be approximately 3.8 km/s. Additionally, we experimentally determine the magnon dispersion in CrPS4 by varying the magnon wavevectors and propose an analytical model for the antiferromagnetic magnon dispersion in CrPS4. Our findings open new avenues for energy-efficient magnonic devices based on van der Waals antiferromagnets.
Fine texture Lambertian electromagnetic metasurface generates background blending stealth effect in radar vision
Authors: Yuan Honglin , Sun Yingjian , Huang Yixing , Sun Weibin , Li Qun , Li Ying
Published: January 2025

The emergence of diffuse scattering metasurfaces offers the electromagnetic scattering stealth mechanism. However, the background blending stealth effect in radar vision induced by diffuse scattering metasurface has not been specially investigated. Here, a background blending Lambertian diffusive reflective metasurface for imaging radar stealth is designed by electromagnetic dispersion engineering. Compared to a conventional metasurface, the Lambertian metasurface achieves more uniform beam dispersion over a broad frequency range without significant main lobe formation at any frequency point, which provides ways for background fusion stealth. For conceptual validation, a metallic flat plate, coded metasurface, and Lambertian metasurface are fabricated and their radar images are obtained by two-dimensional imaging scanning measurement. As anticipated, the Lambertian metasurface notably alters the imaging edge characteristics in the radar images, effectively concealing the contours of the covered area. This work provides a wideband design method of the coded metasurface, which provides a new idea for designing stealth material and structures from the perspective of radar imaging and is immensely helpful for practical application in jamming recognition stealth of coding metasurfaces.
Numerical investigation of gap spacing and Reynolds number effects on unconfined flow around staggered square cylinders
Authors: Sohankar A. , Harandifasih K. , Mashhadi A.
Published: January 2025

This numerical study presents laminar, two-dimensional analyses of unconfined flow over two staggered square cylinders, oriented at a 45° angle relative to the incoming flow direction. The investigation examines six center-to-center gap spacing: S = 2D, 3D, 4D, 6D, 8D, 10D, and 12D, where D indicates the side length of the cylinders. The study covers a broad range of Reynolds numbers (Re), from 1 to 200, encompassing creeping, steady, and unsteady flow regimes. The primary objective is to assess the effects of both Re and S/D on flow patterns and associated quantities. Furthermore, the impact of computational domain size on the results for varying Re is examined. Another aim is to determine the critical Reynolds numbers (Recr) that trigger the onset of vortex shedding. The findings reveal that as S/D increases, Recr rises, gradually approaching the Recr value associated with a single cylinder. Four distinct time-averaged flow patterns are identified based on streamlines analysis. Generally, the downstream cylinder exerts a controlling influence on the flow dynamics of the upstream cylinder, while the upstream cylinder enhances vortex shedding from the downstream counterpart. The impact of Re and S/D on comprehensive aerodynamic characteristics is attributed to their contributions to determine the flow regime and pattern, the degree of vortex merging occurring behind the cylinders, and the flow intensity in the interstitial space. However, the significance of S becomes less pronounced for inter-cylinder distances exceeding 4D, due to diminished mutual interaction effects between the flows passing around the cylinders.
Rationalizing protein–ligand interactions via the effective fragment potential method and structural data from classical molecular dynamics
Authors: Urbina Andres S. , Slipchenko Lyudmila V.
Published: January 2025

The Effective Fragment Potential (EFP) method, a polarizable quantum mechanics-based force field for describing non-covalent interactions, is utilized to calculate protein–ligand interactions in seven inactive cyclin-dependent kinase 2–ligand complexes, employing structural data from molecular dynamics simulations to assess dynamic and solvent effects. Our results reveal high correlations between experimental binding affinities and EFP interaction energies across all the structural data considered. Using representative structures found by clustering analysis and excluding water molecules yields the highest correlation (R2 of 0.95). In addition, the EFP pairwise interaction energy decomposition analysis identifies critical interactions between the ligands and protein residues and provides insight into their nature. Overall, this study indicates the potential applications of the EFP method in structure-based drug design.
Spreading and rebound of viscoelastic droplets on surfaces with hybrid wettability
Authors: Mousavi Mahmood , Faroughi Salah A.
Published: January 2025

Understanding viscoelastic droplet impact dynamics on solid surfaces is crucial for various industrial applications, including fuel injection, spray coating, inkjet printing, and microfluidics. This study investigates the behavior of a viscoelastic droplet impacting a solid substrate with different wettability properties characterized by different wall contact angles (WCA): hydrophilic (10°), hydrophobic (160°), and a hybrid surface that combines both properties (10°–160°). This study integrates the Oldroyd-B viscoelastic model with a dynamic contact angle framework to examine the effects of WCA and fluid relaxation time on droplet spreading and rebound behaviors. The findings reveal that surface wettability significantly influences droplet behavior during the spreading and rebound stages, affecting wetted area and droplet shape. On hydrophilic surfaces, droplets exhibit typical rebound behavior with partial attachment, while hydrophobic surfaces induce spreading with smaller contact areas and increased rebound. Notably, hybrid surfaces induce complex, asymmetric droplet dynamics markedly different from surfaces with homogeneous wettability. Increasing a droplet's relaxation time enhances spreading and reduces droplet deformation during the maximum rebound stage, particularly on the hydrophobic part of hybrid surfaces. In contrast, reduced relaxation times result in an increase in the height of the droplet during the rebound stage.
Generation of vector vortex pin-like beams and their propagation in turbulent atmosphere
Authors: Li Jia , Liang Huijian , Wu Gaofeng , Peng Peipei , Wang Fei , Cai Yangjian
Published: January 2025

Atmospheric turbulence consistently poses a significant challenge to the stable propagation of laser beams, particularly over long distances, as is often the case in free-space optical communication systems. To mitigate the adverse effects of atmospheric turbulence, there is a pressing need to develop specialized laser beams. In this study, we analyzed and derived the propagation characteristics of vector vortex pin beams (VVPBs) in free space and simulated their behavior under atmospheric turbulence using numerical methods. Our simulations demonstrate that, under identical conditions, VVPBs exhibit lower scintillation indices and beam wander compared to pin beams (PBs) over long distances. Furthermore, we experimentally generated VVPBs and PBs and measured their scintillation indices and beam wander as they traversed thermally induced turbulence in a laboratory setting. The experimental data corroborate our theoretical findings, confirming that VVPBs offer significant advantages in reducing the impact of turbulence. These findings could have substantial implications for the advancement of free-space optical communication and remote sensing technologies.
Achieving effective photoluminescence control in two-dimensional van der Waals transition metal dichalcogenide heterostructures via laser-modified ozone intercalation
Authors: Song Junming , Yu Yuanfang , Zheng Ting , Cui Yueying , Chen Qiushi , Zhao Weiwei , Yang Fang , Lu Junpeng , Liu Hongwei , Ni Zhenhua
Published: January 2025

The integration of two-dimensional transition metal dichalcogenide (TMD) layers into van der Waals (vdW) heterostructures offers substantial opportunities for both materials synthesis and device design. Interlayer interactions enable desirable functionalities, and manipulating these interactions is essential for optimizing device performance. In this work, we introduce ozone intercalation into vdW heterostructures and adopt laser irradiation as a manipulation tool, creating a photoluminescence (PL)-based modulation type using interface engineering. Interlayer engineering can be quantitatively achieved by precisely controlling the laser modification time, enabling a controllable PL intensity from no quenching to quenching. The mechanism behind this regulation can be attributed to the interlayer exciton suppression introduced by ozone intercalation being repaired by ozone molecule reduction during the laser treatment. This effective regulatory technique is universal and can be achieved in various type II band-aligned TMD heterostructures, providing an intriguing strategy for the design of two-dimensional vdW TMD device systems.
Wave-breaking phenomena around a wedge-shaped bow
Authors: Wang Jianhua , Shao Yuming , Li Xinyi , Mao Tianyi , Wan Decheng
Published: January 2025

Bow wave breaking has long been a research challenge in the research field of ship hydrodynamic. This study simplifies the ship's bow as a three-dimensional wedge-shaped structure and conducts experimental measurements to investigate the dynamic characteristics of bow wave breaking. The experiments are carried out in a recirculating water channel, with the force transducer and wave height probes used for measurement. The complex mechanisms influencing bow wave breaking in real-world scenarios can be influenced by factors such as flow velocity, draft, flooding angle, flare angle, and yaw angle. Experiments are carried out under various conditions by controlling one factor at a time. The results show that more intense wave breaking not only increases the resistance force on the wedge but also raises the wave height of the measuring point in the non-breaking region and the nonlinearity in the breaking region. The high-frequency fluctuations of wave height in the breaking region become more obvious. Through a quantitative comparison of different factors on the wave-breaking phenomena, it can be found that the flooding angle has a significant impact on resistance, which helps explain why slender hull designs are commonly used for fast ships. The yaw angle plays a crucial role in affecting the bow waves, influencing both stable wave height and nonlinear breaking waves. The measurement results presented in this paper can provide valuable validation data and flow insights for studies on ship bow wave breaking.
Review of Scientific Instruments New Products
Authors: Mandelis Andreas
Published: January 2025

In order to supplement manufacturers’ information, this department will welcome the submission by our readers of brief communications reporting measurements on the physical properties of materials that supersede earlier data or suggest new research applications.