Dispersion Law Research Articles

Plasmons in semiconductor and topological insulator wires with large dielectric constant

The dispersion law of plasmons running along thin wires with radius a is known to be practically linear. We show that in wires with a dielectric constant κ much larger than that of its environment κe, such dispersion law crosses over to a dispersionless three-dimensional-like law when the plasmon wavelength becomes shorter than the length (a/2)(κ/κe)ln(κ/2κe) at which the electric field lines of a point charge exit from the wire to the environment. This happens both in trivial semiconductor wires and wires of three-dimensional topological insulators.

Dispersion of ICT-related subject terms in information and knowledge management publications: A Bradford analysis

The application of information and communication technologies (ICTs) in information and knowledge management (IKM) has attracted the attention of library and information Science (LIS) scholars in the recent past. The multidisciplinary and interdisciplinary nature of ICTs means that the ICT literature is published in several fields of knowledge. Although Bradford’s law of dispersion is commonly used to determine the core journals in a given field or discipline or topic of study, this study attempts to use the principles of the law to determine the core concepts of ICTs within the information and knowledge management literature. Data was obtained from EBSCO Discovery’s Library, Information Science and Technology s (LISTA) and the Library and Information Science Source (LISS) databases using a variety of keywords as search terms. The procedures of conducting a Bradford analysis were followed to determine the core subject terms in ICTs as reflected in the IKM group of articles published between 1998 and 2017. The results indicate that the application of ICTs in IKM largely occurs in the fields medicine, business and commerce, education and training (higher education and training), decision sciences, and industrial management. It was also noted that the core subjects varied from one study period to another; technology-associated subject terms were largely visible; and the dispersion of subject terms fits the Bradford’s dispersion. We however noted that the dispersion of articles according to Bradford’s zones is not accurately representative of the principles of the Law. The study has implications for collection development, searching and retrieval practices, and the application of Bradford’s law beyond the analysis of core journals or publications in not only IKM but also in the field of library and information science.

Universal Structural and Dynamic Features in Metals Near Their Melting Points

The results of a comparative analysis of experimental data for the equilibrium properties and characteristics of liquid alkaline earth (magnesium, calcium, strontium), alkaline (lithium, sodium, potassium) and transition metal groups: elements of the subgroups of nickel (Ni, Pd, Pt) and copper (Cu, Ag, Au) near their melting points are presented. Reduced spatial r/rm = rkm /2π and time scales, in which km is the first peak position of the static structure factor S(k) and β = 1/kBT is the inverse temperature, are introduced as the basis for the law of corresponding states. Based on these scale transformations and x-ray diffraction analysis, it was found that the groups of liquid alkaline, alkaline earth, and transition metals are described by universal r- and k- dependencies. It has been established that the dispersion law of longitudinal polarization ωc (k), given in accordance with these scale relations, for elements of groups of liquid alkaline, alkaline earth and transition metals has a single universal character. An analysis of the properties of three groups (alkaline, alkaline earth and transition) liquid metals using scale transformations shows that the law of the corresponding states is valid for these substances.

A Numerical Investigation of the Dispersion Law of Materials by Means of Multi-Length TDR Data

In this paper, we propose a method for retrieving the dispersion law of a material under test from multi-length TDR measurements in reflection mode, repeated at several frequencies. By replacing the multi-frequency measurements with measurements using multi-length TDR probe, it is possible to retrieve the complex equivalent permittivity of the material in a frequency band of interest. The proposed procedure does not require a priori knowledge of the type of dispersion law of the material, which instead can possibly be inferred from the measured data. The algorithm is validated using numerically simulated data obtained with the commercial code CST Microstudio®.

Oxygen nonstoichiometry and magnetic properties of doped manganites La0.7Sr0.3Mn0.95Fe0.05O3-δ

In this work, solid solutions of La0.7Sr0.3Mn0.95Fe0.05O3-δ with different oxygen content were obtained by the solid-phase reactions technique. Based on the investigation of the dynamics of changes in the oxygen index (3 – δ) during heating of the samples, the formation of a stressed state in their grains as a result of annealing was established. This results in a decrease in the mobility of oxygen vacancies during the reduction of cations according to the Mn4+ + e– → Mn3+ scheme and explains the decrease of released oxygen amount with an increase of δ as well as the heating rate of the samples. When studying the magnetic properties of the obtained samples, it was found that the temperature dependence of the magnetization obeys the Curie–Weiss law and as the oxygen defficiency increases, the Curie temperature for solid solutions decreases. It was found that the particles are in a frozen ferromagnetic state when measured in the low-temperature region of the М(Т) dependence in “zero-field mode” at Т ˂ ТВ. The presence of ferromagnetism at Т ˃ ТВ leads to a magnetically ordered state, in which the resulting magnetic moment of the magnetic particle is influenced by thermal fluctuations. When considering the temperature values of the magnetization of lanthanum-strontium manganite samples, it was found that with an increase of temperature in the low-temperature region, magnetic ordering is disturbed due to the excitation of magnons with a quadratic dependence of the energy from the wave vector, the number of which increases in proportion to T3/2. This results in a decrease in the manganite magnetization. The observed temperature dependence of the magnetization measured in the “field-cooling mode” was approximated taking into account the quadratic and non-quadratic dispersion laws of the magnon spectrum.

Dispersion Law and Decrement of Superluminal Surface Wave in Josephson Sandwich

Dispersion Law and Decrement of Superluminal Surface Wave in Josephson Sandwich

Flat and almost flat bands in the quasi-one-dimensional Josephson junction array

The dispersion law for the linear waves in the quasi-one-dimensional array of inductively coupled Josephson junctions (JJs) is derived. The array has a multiladder structure that consists of the finite number of rows (N ⩾ 2) in Y direction and is infinite in X direction. The spectrum of the linear waves (Josephson plasmons) consists of 2N − 1 branches. Among these branches there is an N-fold completely flat degenerate one that coincides with the Josephson plasma frequency. The remaining N − 1 branches have a standard Josephson plasmon dispersion law typical for 1D JJ arrays. Application of the uniform dc bias on the top of each vertical column of junctions lifts the degeneracy and only one flat branch remains unchanged. The rest of the previously flat branches become weakly dispersive. The parameter range where the flatness of these branches is maximal has been discussed.

Emission of conical THz radiation induced by bichromatic pumpXwaves in an air plasma

The $X$-wave formation during the propagation of bichromatic femtosecond laser pulses in an air plasma filament and THz radiation generation has been investigated both experimentally and theoretically. We found that in this case the pump waves as well as THz radiation propagate as $X$ waves at the same group velocity. Therefore, the cone angle of generated THz radiation could be estimated using the $X$-wave dispersion law. Hence, the proposed model allows an alternative characterization of generated THz radiation based on the frequency-angular spectra of pump waves registered after propagation in the created plasma filament.

Seismic surface wave attenuation by resonant metasurfaces on stratified soil

AbstractThis study aims to theoretically and numerically investigate the dispersion relations of Rayleigh waves propagating through vertical oscillators periodically distributed on stratified media. The classical elastodynamics theory and an effective medium approximation method are adopted to describe the dynamic behavior of metasurfaces and hybridization between the local oscillators and the foundational surface wave modes. The Abo‐zena algorithm and delta‐matrix method are combined to simplify the Eigen equation to overcome the accuracy problem in solving the closed‐form dispersion laws and improve the computational efficiency. Subsequently, plane‐strain finite element (FE) models with three configurations are developed to confirm the analytical predictions and obtain further insight into the resonator‐Rayleigh wave coupling mechanism. The numerical results are in good agreement with the analytical solutions, revealing that only the foundational mode is strongly coupled with the vertical resonators at resonance, while the surface wave band gap reported in homogeneous media is crossed by the remaining higher‐order surface modes. The attenuation performance and mechanical behavior of a finite‐length metasurface are investigated, and it is demonstrated that the output surface ground motion can be significantly reduced in a narrow frequency band near resonance. Moreover, a graded resonant metasurface with decreasing frequency is simulated to assess the feasibility of broadband attenuation. In summary, the aforementioned analytical framework and numerical simulation results show that the vertical oscillators placed atop a stratified soil system can be designed as resonant metasurfaces for shielding seismic surface waves to protect multiple large infrastructures or special structures from earthquake hazards.

Influence of quantum well parameters on the spectrum of two-dimensional plasmons in HgTe/CdHgTe heterostructures

Influence of parameters of a quantum well and electronic polarizability spatial dispersion on the dependence of two-dimensional plasmon energy on wave vector in narrow-gap CdHgTe quantum wells (band gap 35 meV) is studied theoretically. It is shown that at energies above 20 meV, the dispersion law of two-dimensional plasmons is close to linear. Taking into account the finite width of the quantum well decreases the plasmon phase velocity. This effect increases with an increase in the fraction of cadmium in the QW while maintaining the band gap and with a decrease in the concentration of charge carriers in it. Keywords: two-dimensional plasmon, narrow-gap HgTe.

Influence of a quantizing magnetic field on the Fermi energy oscillations in two-dimensional semiconductors

In this article we investigated the effects of quantizing magnetic field and temperature on Fermi energy oscillations in nanoscale semiconductor materials. It is shown that the Fermi energy of a nanoscale semiconductor material in a quantized magnetic field is quantized. The distribution of the Fermi-Dirac function is calculated in low-dimensional semiconductors at weak magnetic fields and high temperatures. The proposed theory explains the experimental results in two-dimensional semiconductor structures with a parabolic dispersion law.

Simulation Analysis of Ammonia Leakage and Dispersion in a Large-Scale Refrigeration System

The use of ammonia in large-scale refrigeration systems (such as those used for a stadium) requires adequate ammonia leakage prevention mechanisms are put in place. In the present study, numerical simulations have been conducted to study the dispersion law in the ammonia machinery room of the refrigeration system for the 2022 Beijing Winter Olympics. The wind speed, and release location have been varied to investigate their effects on the dispersion profile. Different positions of the leakage points in the ammonia storage tank have been found to lead to different areas affected accordingly. In general, the dangerous region area decreases with an increase in the wind speed. However, when the wind is aligned with the leakage direction, this trend is reverted. The study may offer an effective method to predict the impact of ammonia dispersion and implement the safe operation of such large-scale systems.

A Realistic Interpretation of Quantum Wavefunctions as Temperature Dependent Vacuum Polarization Waves

We discuss in this paper a novel interpretation of Born rule as an approximated thermodynamic law which emerges from the interaction of a quantum system with a non-stationary thermal bath associated to vacuum fluctuations induced by external environment radiation. In particular we assume that vacuum polarization is a real non relativistic phenomena caused by hidden vacuum charge oscillations which diffuses heat energy in a dispersive and dissipative dielectric medium with a temperature dependent speed of propagation. We propose a model which couples vacuum wavefunctions to vacuum charge fluctuations and we deduce a temperature dependent running fine structure constant function proportional, at first approximation, to the squared of the effective electron charge and compatible with known experimental data. We interpret the vacuum symmetry breaking energy fluctuations induced in scattering experiments of particle physics and in laser assisted nuclear reactions as thermal quasi-monochromatic beams produced by the decay of hidden non equilibrium massive photons propagating with a variable light speed. We suggest, exploiting an old analogy between plasmons and pseudo Goldstone bosons, to interpret heat diffusion of this non relativistic polarized vacuum as a real De Broglie electromagnetic scalar wave associated to the radiation emitted by the hidden massive photons with acceleration proportional to vacuum Unruh like temperature. We predict a temperature dependent deviation from Coulomb law and a generalized dispersive law of these hidden unstable photons that could be revealed as not stationary coloured noise in experiments on anomalous heat diffusions associated to the decay of unstable accelerated pairs produced in nuclear physics experiments. We discuss then how our proposal of a temperature dependent non relativistic vacuum polarization might be applied to deduce a dynamic generalization of Born rule based on a realistic interpretation of quantum wavefunctions as averaged electromagnetic waves of hidden massive photons. Finally we suggest to test our time asymmetric model looking for very fast oscillating polarization thermal waves emitted during the not instantaneous wavefunction collapse and revealed as not stationary bulk heating effects in experiments on accelerated conductors and nanoconductors.

Anisotropy and size effects in Bi1-xSbx semiconductor wires in a magnetic field

The electron transport and longitudinal and transverse magnetoresistance (MR) of glass-insulated Bi0.92Sb0.08 single-crystal wires with diameters of 180 nm to 2.2 μm and the (1011) orientation along the wire axis have been studied. The wires have been prepared by liquid-phase casting. It has been first found that the energy gap ΔE increases by a factor of 4 with a decrease in wire diameter d due to the manifestation of the quantum size effect, which can occur under conditions of a linear energy–momentum dispersion law characteristic of both the gapless state and the surface states in topological insulators (TIs). It has been revealed that, in strong magnetic fields at low temperatures, a semiconductor–semimetal transition occurs, which is evident as an anomalous decrease in the transverse MR anisotropy and the appearance of a metallic temperature dependence of resistance at T < 100 K. It has been found that the effect of negative MR, the appearance of an anomalous maximum in the longitudinal MR, and the dependence of Hmax ~ d-1 at 4.2 K is a manifestation of the classical MacDonald–Chambers size effect. The calculated value of the component of the Fermi momentum perpendicular to the magnetic induction vector H is 2 times higher than the value for pure bismuth wires. The features of the manifestation of the quantum size effect in Bi0.92Sb0.08 wires, semiconductor–semimetal electronic transitions induced by a magnetic field, and a decrease in the transverse MR anisotropy indicate the occurrence of new effects in low-dimensional structures based on semiconductor wire TIs, which require new scientific approaches and applications.

Transverse thermo-magnetic effect in double-periodic semiconductor superlattice at the lack of inversion symmetry

The surface density of charge current in two-dimensional double-periodic n-type semiconductor superlattices is calculated in the one-electron approximation in an external magnetic field in the presence of a temperature gradient. The magnetic field was assumed to be constant, uniform, applied perpendicular to the plane of the electron gas. The joint solution of the Schrodinger equation and the kinetic Boltzmann equation is shown that the dependence of the transverse surface density of the current about temperature and module temperature gradient are significantly non-linear in nature, there are areas with negative differential conductivity. The dependence of the relaxation time on the quasi-momentum of the electron is taken into account in the model phenomenologically through the dispersion law of carrier in magnetic subbands. At the lack of inversion symmetry the dispersion laws of magnetic subbands are not even functions of the quasimomentum defined in magnetic Brillouin zone. As a result, the transverse surface thermo-magnetic current increases in many times in comparison with symmetric case Keywords: thermo-magnetic effect, two-dimensional doubly periodic semiconductor superlattices.

Положения экстремумов зонного спектра носителей заряда в тонких пленках висмута

Many studies report an increase in charge carrier concentration in thin bismuth films as their thickness decreases at low temperatures. These results are obtained on the basis of data on resistivity, magnetoresistance, Hall coefficient, and thermal EMF measured in these films. The calculation is most often carried out within the framework of the two-band approximation assuming the quadraticity of the dispersion law of electrons and holes. Using these approximations, it is possible to estimate the change in the position of energy extremes relative to the chemical potential in these films based on concentration values of charge carriers. This article presents all these calculations and analyses the extrema movement of the charge carrier band spectrum in bismuth films with a change in their thickness.

Поверхностные электромагнитные волны Дьяконова на границе раздела анизотропных двуосных кристаллов

A general approach to analysis of Dyakonov surface waves at the interfaces of anisotropic biaxial crystals is proposed, taking into account arbitrary spatial orientation of the media tensors principal axes. This approach is based on the operator representation of macroscopic Maxwell equations corresponding to the quantum-mechanical equations for photon states in an inhomogeneous anisotropic media. Surface wave dispersion law is investigated in the most general case. It is established that the interface eigenmode dispersion is closely related to the dispersion of bulk waves in the partnering media, which is a specific feature of Dyakonov waves. The electromagnetic field spatial distribution is investigated in the direction orthogonal to the boundary plane. The surface wave angular existence domain is determined. It’s dependencies on the rotation angles of the media optical axes are studied as well.

Dyakonov Surface Waves at the Boundary of Anisotropic Biaxial Crystals

A general approach to analysis of Dyakonov surface waves at the interfaces of anisotropic biaxial crystals is proposed, taking into account arbitrary spatial orientation of the media tensors principal axes. This approach is based on the operator representation of macroscopic Maxwell equations corresponding to the quantum-mechanical equations for photon states in an inhomogeneous anisotropic media. Surface wave dispersion law is investigated in the most general case. It is established that the interface eigenmode dispersion is closely related to the dispersion of bulk waves in the partnering media, which is a specific feature of Dyakonov waves. The electromagnetic field spatial distribution is investigated in the direction orthogonal to the boundary plane. The surface wave angular existence domain is determined. It's dependencies on the rotation angles of the media optical axes are studied as well. Keywords: electromagnetic surface waves, interface photon states, anisotropic media, biaxial materials.

Oxygen nonstoichiometry and magnetic properties of doped manganites La0.7Sr0.3Mn0.95Fe0.05O3-δ

In this work, solid solutions of La0.7Sr0.3Mn0.95Fe0.05O3-δ with different oxygen content were obtained by the solid-phase reactions technique. Based on the investigation of the dynamics of changes in the oxygen index (3 – δ) during heating of the samples, the formation of a stressed state in their grains as a result of annealing was established. This results in a decrease in the mobility of oxygen vacancies during the reduction of cations according to the Mn4+ + e– → Mn3+ scheme and explains the decrease of released oxygen amount with an increase of δ as well as the heating rate of the samples. When studying the magnetic properties of the obtained samples, it was found that the temperature dependence of the magnetization obeys the Curie–Weiss law and as the oxygen defficiency increases, the Curie temperature for solid solutions decreases. It was found that the particles are in a frozen ferromagnetic state when measured in the low-temperature region of the М (Т) dependence in “zero-field mode” at Т ˂ ТВ. The presence of ferromagnetism at Т ˃ ТВ leads to a magnetically ordered state, in which the resulting magnetic moment of the magnetic particle is influenced by thermal fluctuations. When considering the temperature values of the magnetization of lanthanum-strontium manganite samples, it was found that with an increase of temperature in the low-temperature region, magnetic ordering is disturbed due to the excitation of magnons with a quadratic dependence of the energy from the wave vector, the number of which increases in proportion to T3/2. This results in a decrease in the manganite magnetization. The observed temperature dependence of the magnetization measured in the “field-cooling mode” was approximated taking into account the quadratic and non-quadratic dispersion laws of the magnon spectrum.

On the group velocity of whistling atmospherics

The dynamic spectrum of a whistling atmospheric is a signal of falling tone, and the group delay time of the signal as a function of frequency is formed as a result of propagation of a broadband pulse in a medium (magnetospheric plasma) with a quadratic dispersion law. In this paper, we show that for quadratic dispersion the group velocity is invariant under Galilean transformations. This means that, contrary to expectations, the group velocity is paradoxically independent of the velocity of the medium relative to the observer. A general invariance condition is found in the form of a differential equation. To explain the paradox, we introduce the concept of the dynamic spectrum of Green’s function of the path of propagation of electromagnetic waves from a pulse source (lightning discharge in the case of a whistling atmospheric) in a dispersive medium. We emphasize the importance of taking into account the motion of plasma in the experimental and theoretical study of electromagnetic wave phenomena in near-Earth space.