Harmonic Electric Field Research Articles

Harmonic Analysis of the Polarization Reversal of the Rb2ZnCl4 Crystal in the Incommensurate Phase

The polarization reversal of Rb2ZnCl4 crystals in the incommensurate phase near a ferroelectric phase transition (PT) under the action of harmonic electric field has been studied using harmonic analysis. During polarization reversal of a test sample under the action of harmonic electric field, a PT induced by the electric field from the incommensurate phase to the ferroelectric phase and a PT from the field-induced ferroelectric phase back to the incommensurate phase occur. The study of the active and reactive contributions to the amplitudes of current density harmonics made it possible to determine the current values of harmonic electric field intensity at which the corresponding PTs occur.

Influence of rippled density and laser profile on third harmonic generation using cosh‐Gaussian laser pulses in inhomogeneous magnetized plasmas

AbstractThe third harmonic generation of cosh‐Gaussian laser pulses in inhomogeneous magnetized plasmas is investigated. The plasma is considered inhomogeneous with a sinusoidal form, and the external magnetic field has an oscillating wiggler structure. Various ponderomotive forces are obtained considering the external magnetic field, the magnetic field of the laser beam, and different orders of electron velocity. These forces are nonlinear, which leads to a nonlinear current density. Using linear and nonlinear current densities and Maxwell's equations, the wave equation of the third harmonic wave is obtained. Results show that by increasing the deviation parameter from the center and the external magnetic field, the third harmonic electric field increases. It is also indicated that by increasing the laser beam width, the excited electric field decreases. Finally, it is found that by increasing the wavenumber and amplitude of the rippled electron density, the amplitude of the third harmonic electric field increases.

Influence of the axial oscillations on the electron cyclotron drift instability and electron transport in Hall thrusters

A 2D-3V finite-element particle-in-cell model, which is applied to simulate the radial-azimuthal plane near the exit of Hall thrusters, has been presented to investigate the influence of axial oscillation on electron cyclotron drift instability (ECDI) and anomalous cross field electron transports. The simplified theoretical analysis about the ECDI and the anomalous electron transport has been introduced. The uniform and harmonic axial electric fields, which are based on the typical axial oscillations in Hall thrusters, have been considered in the simulations. It is concluded that different constant axial electric fields can influence the properties of instability but cannot significantly change the cross field electron mobility. However, the axial oscillation plays a significant role in the instability, and the electron transports provided that appropriate amplitudes and frequencies are achieved. The equilibrium of the instability is destroyed and reformed with the axial oscillation. The cross field electron transports are enhanced in the range of low amplitudes and frequencies and are suppressed when they are in a high value. In addition, it is observed that the variation of the electron mobility and electron–ion friction force show high consistency with the trend of electron temperature. It is further confirmed that the increase in electron temperature takes responsibility for the enhanced cross field electron transport due to the axial oscillation.

Band structure for relativistic charge carriers submitted to a helical electric field

We study the relativistic dynamics of electrons submitted to a uniform harmonic electric fields longitudinally applied to the electron velocity. In order to obtain explicitly the set of time-dependent equations for the bi-spinors components, we write down the corresponding Dirac equation for this system. By performing a suitable transformation to this set of equations, we get a matrix equation whose eigenvalues can be found directly. We found analytically the band structure and show a break of degeneracy and the existence of three bands: two total and one partial. The thicker band preventing from the Schwinger mechanisms can be shortened by proper combination of the frequency and amplitude of the applied electric field.

The superposed electric field effect on the charge transport and polaron formation in molecular crystals

We study the polaron formation and its mobility in a one-dimensional molecular crystal subjected to superposed static and harmonic electric fields. Such molecular chain exhibits intermolecular vibrational degrees of freedom, which makes the carrier-lattice interaction an important parameter of the system. By exploring field settings in which the preferential transport occurs, we show the existence of different small polaron formations, including those that travel close to the sound velocity or that are stationary by self-trapping. Electric fields magnitudes and carrier-lattice coupling have also been analyzed, which allowed to show a phase diagram that describes the existing regimes. In addition to thresholds between the mobile and stationary polaron regimes, this phase diagram unveils an unusual aspect: a metastable polaron formation.

Parametric studies of stream instability-induced higher harmonics in plasma ionization breakdown near an emissive dielectric surface

In this work, we comprehensively investigate the generation of higher harmonic (HH) electric fields normal to the applied rf electric field in multipactor-coexisting plasma breakdown by fully kinetic particle-in-cell (PIC) simulations and a theoretical model. Firstly, a base case at driving frequency 1 GHz, transverse rf electric field amplitude 3 MV m−1, and background gas pressure 0.2 Torr, is studied in detail. The enhanced harmonic frequency observed is around ten times the fundamental rf frequency, significantly lower than the Langmuir frequency. A theoretical model reveals that the fundamental mechanism of HHs generation is stream–plasma instability, which originates from stream-like secondary electron emission interacting with plasma. The resulting HH frequency and the growth rate of its oscillating amplitude from the theoretical model, agree well with the PIC simulations. With increasing pressure, the HH oscillations are found to be significantly reduced. This is because at higher pressure the gas ionization rate is higher, which causes a more rapidly increasing plasma density, leaving less time for the growth of instability. Furthermore, the parameter space in terms of background gas pressure and rf field amplitude within which the HHs appear is revealed. Finally, the effect of the driving rf frequency on HHs is also investigated, and it is found that the instability-induced oscillating HHs field remains when the driving frequency is increased to 2 GHz, however, it is highly reduced at higher driving frequency of 5 GHz, as oscillations at the fundamental frequency start playing a more important role.

Noise generation in a bilayer ferromagnet-piezoelectric heterostructure at the converse magnetoelectric effect

The paper describes first observation of parametric generation of noise in a composite multiferroic resonator. Resonator of a disk shape contains two mechanically coupled layers, one of which is the amorphous ferromagnet (FM) FeBSiC and the other is the piezoelectric (PE) lead zirconate titanate. DC magnetic field of 0–100 Oe is applied parallel to the plane of the resonator. Resonator is excited in the frequency range f = 2–10 kHz by a harmonic electric field with amplitude of up to 330 V cm−1 applied to the PE layer. Changes in the magnetization of the resonator caused by the converse magnetoelectric effect were recorded using an electromagnetic coil. With an increase in the excitation field to the threshold value, the parametric generation of harmonics and subharmonics with a discrete spectrum is observed, which then turns into a stochastic mode and a continuous spectrum of frequencies is generated. Noise density is hysterically dependent on the excitation field and non-monotonically depends on the dc magnetic field. Theory of parametric generation of the noise in a multiferroic resonator is developed, taking into account excitation of acoustic resonances and magnetoacoustic nonlinearity of the FM layer of the resonator. Theory, qualitatively describes the main characteristics of noise generation.

Thermally improved crystalline phase and intercalated PEO/OMMT nanocomposites for high to ultrahigh radio frequency range low‐permittivity nanodielectrics

AbstractPoly(ethylene oxide) (PEO)/organomodified‐montmorillonite (OMMT) nanoclay based nanocomposites having 1, 3, 5, 10, and 20 wt% OMMT nanofiller were prepared by homogeneous mixing and the melt‐compounding method. These hybrid materials were characterized by employing X‐ray diffractometer, differential scanning calorimeter, and radio frequency impedance analyzer. The experimental results confirmed the formation of OMMT intercalated structures with reduced crystallinity and increased melting temperature of PEO crystallites which are predominantly ruled by the nanofiller amounts in the PEO/OMMT nanocomposites. Dielectric permittivity of these nanocomposites measured at 20°C exhibited a gradual decrease with increasing frequencies of the applied harmonic electric field of high to ultrahigh range (i.e., 1 MHz–1 GHz), but it changed anomalously in the range of 2.6–3.6 with the increase of OMMT amounts in the PEO matrix. The dielectric losses in these composites were found low and their loss spectra exhibited a hydrogen bond dipolar reorientation relaxation process around 1 GHz. The alternating current electrical conductivity of these nanocomposites increased with frequency and also changed with the OMMT concentrations. These PEO/OMMT nanocomposites are classified as low permittivity nanodielectrics which could be potential candidates for advances in flexible and biodegradable radio‐electronic devices.

The study of the temporal evolution of the electric energy dependence on polarization in Rb2ZnCl4 crystal in ferroelectric phase near the Curie point

The process of Rb2ZnCl4 crystal repolarization under the harmonic electric field influence in the ferroelectric phase near the Curie temperature was studied by the harmonic analysis method. The study of current density harmonics arising in the sample under the harmonic field influence allowed plotting the electric energy density Wc dependence on the polarization Pc measured in the dynamics. The Wc (Pc ) time evolution was obtained after shifting of the domain structure from the equilibrium position by an alternating electric field. It was found that during relaxation the shape of Wc (Pc ) changed significantly.

Thermal and electrical characterization of poly(vinyl)alcohol)/poly(vinylidene fluoride) blends reinforced with nano-graphene platelets

Nano-graphene/polymer composites can function as pressure induced electro-switches, at concentrations around their conductivity percolation threshold. Close to the critical point, the pressure dependence of the electron tunneling through the polymer barrier separating nano-graphene's results from the competition among shortening of the tunneling length and the increase of the polymer's polarizability. Such switching behavior was recently observed in polyvinyl alcohol (PVA) loaded with nano-graphene platelets (NGPs). In this work, PVA is blended with α-poly(vinylidene fluoride) (PVdF) and NGPs. Coaxial mechanical stress and electric field render the nano-composite piezoelectric. We investigate the influence of heterogeneity, thermal properties, phase transitions and kinetic processes occurring in the polymer matrix on the macroscopic electrical conductivity and interfacial polarization in casted specimens. Furthermore, the effect of electro-activity of PVdF grains on the electric and thermal properties are comparatively studied. Broadband Dielectric spectroscopy is employed to resolve and inspect electron transport and trapping with respect to thermal transitions and kinetic processes traced via Differential Scanning Calorimetry. The harmonic electric field applied during a BDS sweep induces volume modifications of the electro-active PVdF grains, while, electro-activity of PVdF grains can disturb the internal electric field that free (or bound) electric. The dc conductivity and dielectric relaxation was found to exhibit weak dependencies.

Bloch-like superoscillations and unidirectional motion of phase-driven quantum walkers

We study the dynamics of a quantum walker simultaneously subjected to time-independent and -dependent phases. Such dynamics emulates a charged quantum particle in a lattice subjected to a superposition of static and harmonic electric fields. With proper settings, we investigate the possibility to induce Bloch-like superoscillations, resulting from a close tuning of the frequency of the harmonic phase $\ensuremath{\omega}$ and that associated with the regular Bloch-like oscillations ${\ensuremath{\omega}}_{B}$. By exploring the frequency spectra of the wave-packet centroid, we are able to distinguish the regimes on which regular and super-Bloch oscillations are predominant. Furthermore, we show that under exact resonant conditions $\ensuremath{\omega}={\ensuremath{\omega}}_{B}$ unidirectional motion is established with the wave-packet average velocity being a function of the quantum coin operator parameter, the relative strengths of the static and harmonic terms, as well as the own phase of the harmonic field. We show that the average drift velocity can be well described within a continuous-time analogous model.

Integrable generalisations of Dirac magnetic monopole

We classify certain integrable (both classical and quantum) generalisations of Dirac magnetic monopole on topological sphere S 2 with constant magnetic field, completing the previous local results by Ferapontov, Sayles and Veselov. We show that there are two integrable families of such generalisations with integrals, which are quadratic in momenta. The first family corresponds to the classical Clebsch systems, which can be interpreted as Dirac magnetic monopole in harmonic electric field. The second family is new and can be written in terms of elliptic functions on sphere S 2 with very special metrics.

Thermodynamic Characterization of Red Blood Cell Suspension and Band 3 Protein Oxy-Deoxygenating Functionality: Comparative Study

Abstract The importance of studying storage alterations in erythrocytes is highlighted by the need to understand changes that could potentially serve to optimize the storage system. With this aim, the non-equilibrium thermodynamic theory with internal variables was introduced, and perturbing the erythrocyte samples with a harmonic electric field some functions of the theory have been determined varying in the perturbation frequency. A frequency has been noted that acts as a separator element between two states showing a different entropy production above and below this frequency. In stored red blood cells compared to fresh ones, the increase in entropy production measured shows a greater state of disorder in the latter. Further alterations have been highlighted on the surface charge density of the stored erythrocyte membrane and on the speed of anionic kinetics. All these observations highlight the image of membrane structural and functional alterations of the stored erythrocytes and lead to the elaboration of a technique able to correlate a specific perturbation frequency with the aging time of red blood cells.

The relief shape changing of the crystal Rb2ZnCl4 electrical energy dependence obtained from polarization in vicinity of the domain structure freezing temperature (T*≈150 K)

The repolarization process of Rb2ZnCl4 crystals under the influence of a harmonic electric field in the ferroelectric phase in the vicinity of the domain structure freezing temperature K was studied using the harmonic analysis method. The study of current density harmonics that occur in the sample under the influence of a harmonic field allowed to build a dependence of the electric energy of the sample volume unit on the polarization measured in dynamics. The temperature evolution of the Rb2ZnCl4 crystal dependency potential relief shape in the ferroelectric phase in the vicinity of the domain structure freezing temperature was investigated.

Temporal Evolution of the Electrical Energy of Rb2ZnCl4 Crystal as a Function of Polarization in the Ferroelectric Phase near the Curie Temperature

The repolarization of Rb2ZnCl4 crystal under the influence of a harmonic electric field in the ferroelectric phase near the Curie temperature is studied via harmonic analysis. Study of the current density harmonics allows construction of the dependence of the density of electrical energy $${{W}_{{\text{c}}}}$$ on polarization $${{P}_{{\text{c}}}}$$ measured in the dynamics, and investigation of the temporal evolution of this dependence after destabilization of the domain structure by an alternating electric field. It is found that the nature of this dependence varies considerably during relaxation.

A thermodynamic characterization of the phenomena evolving in cancer pathology by dielectric relaxation in blood: A new approach by construction of TTM (Thermodynamic Tumor Matrix)

The paper shows a thermodynamic characterization of the phenomena evolving in cancer pathology on the blood. The goal of the study is cancer characterization at stages that cannot be identified by oncologists. In this context, the non-equilibrium thermodynamic approach is exploited to calculate the thermodynamic functions deriving by the complex dielectric constant related to blood measurements after stimulation with a harmonic electric field. Calculated functions allow the construction of a matrix, indicated as Thermodynamic Tumor Matrix (TTM) that, gives detailed and selective information. This procedure allowed to highlight blood changes associated with a decrease in orientation polarization P(1) over time. P(1) attenuation may be explained by the intravasation phenomenon. In this context, negative charged cancer cells polarizing under the effect of the harmonic electric field, generate an opposing field E(1) responsible of the P(1) attenuation in intensity. This hypothesis is confirmed by the measurement of the displacement currents.

Parametric Generation of Subharmonics in a Composite Multiferroic Resonator

Parametric generation of subharmonics in a composite multiferroic resonator is observed and investigated. The resonator has the form of a disk and contains two mechanically coupled layers, one of which is amorphous ferromagnet $\mathrm{Fe}\text{\ensuremath{-}}\mathrm{B}\text{\ensuremath{-}}\mathrm{Si}\text{\ensuremath{-}}\mathrm{C}$ and the other piezoelectric lead zirconate titanate. The resonator is placed inside two planar electromagnetic coils with orthogonal axes. A static magnetic field of 0--100 Oe is applied parallel to the plane of the resonator. The resonator is excited in the frequency range f = 9--10 kHz by either a harmonic magnetic field with an amplitude of up to 5 Oe generated by one of the coils, or a harmonic electric field with an amplitude of up to 500 V/cm applied to the piezoelectric layer. When the pump field is above a certain threshold, generation of a subharmonic of half-frequency (f/2) is observed for three different excitation methods. The first two employed either the direct magnetoelectric effect or the converse magnetoelectric effect, while in the third a transformer system is utilized. The subharmonic is generated in a limited range of pump frequencies and its amplitude is a nonlinear function of both the pump-field amplitude and the strength of static magnetic field. A theory of parametric generation of the subharmonic in a multiferroic resonator is developed, taking into account the magnetoacoustic nonlinearity of the ferromagnetic layer of the structure and excitation of acoustic resonances near the pump and subharmonic frequencies. The theory qualitatively describes the main characteristics of the subharmonic generation.

Anomalous dielectric relaxation in solutions of rigid, dipolar asymmetric-top molecules in spherical solvent

The formulae for linear electric polarization induced by harmonic electric field in liquids composed of rigid noninteracting dipolar and asymmetric-top molecules in spherical solvents are derived. The model of noninertial, anomalous rotational Brownian motion is applied. The fractional rotational diffusion equations are solved and time evolution of the electric polarizability is investigated for the case when a dc-electric field is turned off and for the stationary state case when only an ac-field is present. Numerical analysis of the dispersion and absorption parts of electric polarizability is performed as well as the influence of molecular parameters on so-called Cole-Cole plots is investigated.

Control-oriented model of dielectrophoresis and electrorotation for arbitrarily shaped objects.

The most popular modeling approach for dielectrophoresis (DEP) is the effective multipole (EM) method. It approximates the polarization-induced charge distribution in an object of interest by a set of multipolar moments. The Coulombic interaction of these moments with the external polarizing electric field then gives the DEP force and torque acting on the object. The multipolar moments for objects placed in arbitrary harmonic electric fields are, however, known only for spherical objects. This shape restriction significantly limits the use of the EM method. We present an approach for online (in real time) computation of multipolar moments for objects of arbitrary shapes having even arbitrary internal composition (inhomogeneous objects, more different materials, etc.). We exploit orthonormality of spherical harmonics to extract the multipolar moments from a numerical simulation of the polarized object. This can be done in advance (offline) for a set of external electric fields forming a basis so that the superposition principle can then be used for online operation. DEP force and torque can thus be computed in fractions of a second, which is needed, for example, in model-based control applications. We validate the proposed model against reference numerical solutions obtained using Maxwell stress tensor. We also analyze the importance of the higher-order multipolar moments using a sample case of a Tetris-shaped micro-object placed inside a quadrupolar microelectrode array and exposed to electrorotation. The implementation of the model in Matlab and Comsol is offered for free download.

Group theory description of third harmonic generation in diamond and zincblende lattice

We provide a description that shows the importance in finding a susceptibility tensor in nonlinear optics and apply group theory to derive a fourth rank tensor of Oh point group related to the bulk symmetry of monoatomic diamond semiconductor such as Silicon. It is well known that the fourth rank tensor is closely related to the third order nonlinear susceptibility tensor in nonlinear optics through Neumann’s principle and is crucial to understand third harmonic generation (THG) and electric field induced second harmonic generation (EFISH). Using a general Rodriguez rotation, we were able to obtain a three-dimmensional rotation matrix required to perform the symmetry operations, whereas their reflection matrixes are derived using a Householder fromula. We also show how a Td point group corresponding to zincblende can be obtained by breaking the symmetry of the Oh tensor rather than repeating the tedious procedure when obtaining the Oh tensor. Assuming a driven frequency far from the resonance frequency, we can apply Kleinman symmetry and demonstrate that the number of independent components in the Oh and Td fourth rank tensor is reduced from four to just two.