External Electrostatic Field Research Articles

Dynamic switching between single and double plasmon induced reflection through graphene nanoribbons based structure

The plasmon induced reflection (PIR) effect is investigated for a graphene nanoribbon (GNR) based structure. The proposed structure includes a GNR resonator coupling the filtered mid-infrared incident wave to the output as bright mode, and two vertically aligned GNRs as dark mode, forcing the destructive interference into the bright mode resonator to open the PIR window within the second peak of the transmission spectrum. The effects of the geometrical parameter and chemical potential variations are discussed. Numerical simulations verify dynamic switching between single and double PIR simply by the alignment of the dynamic external electrostatic field, which suits the structure for multi-application device utilization, such as multi-channel-selective-filters, switches, sensors, and fast light applications. The GNR-based structure can be realized on a single spatial plane which makes it simple to implement and suitable for ultra-compact optical integrated applications.

Confinement of an Electron in an Image Potential and an External Electrostatic Field

The quasi-classical approximation is used to determine the positions of the classical turning points upon motion of an electron that is bound by an image field and a constant homogeneous electric field of the same direction. Power expansions of the coordinates of the turning points in a wide range of electron energies and field strengths are obtained. The mechanism of one-dimensional confinement of an electron, which determines a completely discrete spectrum of states, is described. The dependence of the spatial width of the confinement region on the field strength and electron energy is determined. The dependences of the electron energy in different states on the external field strength are calculated numerically. Quasi-classical quantization is performed, and the dependence of the electron energy on the width of the confinement region is determined. The energy interval of a maximum density of electron states is found, which is determined by the dependence of the width of the confinement region on the electric field strength.

Single microwave photon switch controlled by an external electrostatic field

We design a single microwave photon switch through a one-dimensional waveguide coupled with a side Jaynes-Cummings system, namely, a single-mode cavity with an embedded Rydberg atom $^{87}\mathrm{Rb}$. Since the energy spectra of the $^{87}\mathrm{Rb}$ atom depend on the electrostatic field, the $^{87}\mathrm{Rb}$ atom can couple with the cavity in tune and out of tune, corresponding to the switch on and off states, respectively. The influences of the single photon pulse width, cavity dissipation, and Rabi coupling on the on/off ratio are studied in detail by a non-Hermitian Hamiltonian. We find that the on/off ratio can be larger than 100 in a wide parameter space and the decay time and rise time are both about 0.75 ns. Within the master equation of the density matrix we also demonstrate that the on/off ratio can be reduced by the quantum noise but is still large enough for application. The transition energy of the two-level Rydberg atom $^{87}\mathrm{Rb}$ gives the switch operating frequency which is in the range of microwave regime. Accordingly, the switch is viable in practice and has potential in quantum informatics.

Tunable band gaps and transmission behavior of SH waves with oblique incident angle in periodic dielectric elastomer laminates

This work focuses on understanding elastic wave propagation in the periodic dielectric elastomer (DE) laminates with geometry and material properties that can be tuned by an external electric field. In particular, shear horizontal (SH) wave propagation at oblique incidence is investigated using the Dorfmann and Ogden's finite electroelasticity theory and the Dielectric Gent (DG) energy model. Numerical calculations of the dispersion relations and transmission properties are presented. The numerical results show that the SH wave band gaps and transmission coefficient depend on various parameters that can be controlled by the applied external electrostatic field and the incident angle of the SH wave, thus providing a novel strategy for designing flexible phononic structures with tunable properties.

On Ring Waves on the Surface of a Conducting Liquid in an External Uniform Electrostatic Field and under Electrical Breakdown

An expression is derived that relates the frequency of ring capillary and gravitational waves on the surface of the conducting liquid in an external uniform electrostatic field to the physical parameters and an analog of the wavenumber. It is shown that the obtained expression formally has the same appearance as the dispersion equation for plane waves; however, in the case under study, the wavenumber as a characteristic of ring waves has no sense due to the undefined concept of wavelength. The paper considers the possibility of attaining an electric discharge from the surface of the liquid charged in the external electrostatic field, when drops of the same liquid are falling on it.

Deformation of Charged Graphene Membrane

Geometrical capacitors with memory (memcapacitors) are of interest because of potential applications in future computing machines. When employing a buckled membrane as one of the capacitor plates, two possible buckled positions serve as the states of low and high capacitance. Using the hybrid B3LYP/6-31G approximation, we investigate the snap-through transition of neutral and negatively charged buckled graphene membranes under the transverse load and external electrostatic field created by a point charge. Estimations show that the chosen calculation method reproduces the elastic properties of graphene within the limits of experimental error. The obtained results testify to the fact that the membrane charge and external electrostatic field affect notably the threshold snap-through switching force in nanosized membranes and, therefore, should be taken into account in the design and development of such nanodevices.

Surface potential stability of large-area Teflon PTFE electret dosimeters of different thicknesses

The effects of charge polarity and thickness on the surface charge potential stability responses of large-area Teflon polytetrafluoroethylene (PTFE) discs electrostatically charged by a new “modified single point-to-plane corona poling rotating system” were studied. Large-area Teflon discs (6 cm diameter) with 0.2, 0.5 and 1 mm thicknesses were used to produce both negatively or positively charged Teflon discs, at the same charging conditions. The deposited charge potential stability of the Teflon discs of different thicknesses monitored by a non-contacting electrostatic voltmeter for an extended time were monitored up to 77 days. Some inter-related parameters such as surface charge potential and external electrostatic field, internal electrostatic field, surface charge density, and the storage duration were also studied. The thick large-area Teflon disc electrets produced provided a steady-state charge stability on either negative (0.2, 0.5 and 1 mm thick) or positive (1 mm thick) surface charge potentials for the long period studied. The Teflon electret discs produced demonstrated having the highest charge potential stability in thicker electrets (1 mm), either negative or positive polarity, with provision of high potential for different applications in general and radiation protection dosimetry in particular.

Electronic Stark effect for a single molecule: Theoretical UV response

Abstract Theoretical analysis of optical absorption in the vacuum ultra-violet (VUV) region by single molecules placed in external electrostatic fields reveals characteristic absorption spectra completely at variance with their ‘zero-field’ counterparts consequent to appearance, disappearance, splitting, merging and shifts of absorption bands and extensive intensity redistributions. This ‘molecular electronic Stark effect’ can be tracked through electronic excitations involving frontier orbitals, energy-level splitting and shifts, molecular geometry changes and re-orientation, orbital mutation and migration. The UV spectra predicted herein should provide theoretical grounds for experimental endeavors on appraisal and characterization of the effect.

Formation of Surface Plasmon-Polariton Vortices at Reflection from Curvilinear Boundary

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Interplay between morphological and shielding effects in field emission via Schwarz-Christoffel transformation

It is well known that sufficiently strong electrostatic fields are able to change the morphology of Large Area Field Emitters (LAFEs). This phenomenon affects the electrostatic interactions between adjacent sites on a LAFE during field emission and may lead to several consequences, such as: the emitter's degradation, diffusion of absorbed particles on the emitter's surface, deflection due to electrostatic forces, and mechanical stress. These consequences are undesirable for technological applications, since they may significantly affect the macroscopic current density on the LAFE. Despite the technological importance, these processes are not completely understood yet. Moreover, the electrostatic effects due to the proximity between emitters on a LAFE may compete with the morphological ones. The balance between these effects may lead to a non trivial behavior in the apex-Field Enhancement Factor (FEF). The present work intends to study the interplay between proximity and morphological effects by studying a model amenable for an analytical treatment. In order to do that, a conducting system under an external electrostatic field, with a profile limited by two mirror-reflected triangular protrusions on an infinite line, is considered. The FEF near the apex of each emitter is obtained as a function of their shape and the distance between them via a Schwarz-Christoffel transformation. Our results suggest that a tradeoff between morphological and proximity effects on a LAFE may provide an explanation for the observed reduction of the local FEF and its variation at small distances between the emitter sites.

The Stark Effect on the Wave Function of Tritium in Relativistic Condition

Tritium Atom is one of the isotopes of Hydrogen that has two Neutrons in the nucleus and an electron that surrounds the nucleus. The Stark Effect is an effect of a shift or polarization of the atomic spectrum caused by the external electrostatic field. The interaction between the electrons and the external electric field can be reviewed using an approximation method of perturbation theory. The perturbation theory used is a time Independent non-degenerate perturbation and reviewed to second order to obtain correction of Tritium Atomic wave function. The condition that used in the system is a relativistic condition by reviewing the movement of electrons within the Atom. The effects of relativity also affect the correction of the wave function of Atom Tritium in the ground state. Tritium is radioactive material that is still relatively safe, and one of the applications of Tritium Atom is on the battery of betavoltaics (Nano Tritium Battery).

Properties of the electrostatically driven helical plasma state

A novel plasma state has been found [Akçay et al., Phys. Plasmas 24, 052503 (2017)] in the presence of a uniform applied axial magnetic field in periodic cylindrical geometry. This state is driven by external electrostatic fields provided by helical electrodes with a (m=1,n=1) (helical) symmetry where m and n represent the poloidal and axial harmonics. The resulting plasma is a function of the cylinder radius r<rw and helical angle u=mθ−nζ, where θ is the poloidal angle, and ζ=z/R is the normalized axial coordinate in the context of a periodic cylinder. In this reference, the strongly driven form of the state was found to have a strong axial mean current density, with a mean-field line safety factor q0(r) just above the pitch of the electrodes m/n=1 in the interior, where the plasma is nearly force-free. However, at the edge the current density has a component perpendicular to the magnetic field B. This perpendicular current density drives nearly Alfvénic helical plasma flows, a notable feature of these states. This state is being studied for its possible application in DC electrical transformers. We present results on several issues of importance for these applications: the transient leading to the steady state; the twist and writhe of the field lines and their relation with the current density; the properties of the current density streamlines and length of the current density lines connected to the electrodes; the sensitivity to changes in the velocity boundary conditions; the effect of varying the radial resistivity profile; and the effects of a concentrated electrode potential.

Statistics of charge carriers of quantum semiconductor film in the presence of strong lateral electrostatic field

The influence of an external strong electrostatic field on the statistical characteristics of equilibrium free charge carriers in a quasi-two-dimensional structure is considered using an example of an InAs semiconductor quantum film. The analysis is carried out for the case when a strong quantization regime for charge carriers is realized in the film and only the first and second film sub-bands of their quantized motion are occupied. The general analytic expressions for the energy of the quantized motion of charge carriers in a film in the presence of a strong electrostatic field are given. An explicit dependence of the width of the band gap of the sample on the value of the external field is obtained. It is shown that with the increase in the external field, the width of band gap of the sample increases. The calculations and corresponding analytical expressions for the chemical potential, concentration, energy and heat capacity of free charge carriers of an InAs quantum film in the presence of a strong electrostatic field are also presented. It is shown that with an increase in the external electrostatic field, the chemical potential of the system retains its negative sign, but increases by the magnitude. For a given value of the external field, the chemical potential of the system increases linearly with the increase in temperature. It is shown that at a given temperature the carriers’ density decreases with the increase in the external field. At a fixed value of the field, the concentration increases with the increase in temperature. The behavior of the energy and heat capacity of the charge carriers is also determined by the same dependence on the temperature of the system and the magnitude of the external field. It is also shown that the main contribution to the indicated characteristics of the sample is made namely by the first filled sub-band of quantized motion of charge carriers. If the second sub-band is also filled, its contribution to the determination of the statistical characteristics of the sample is exponentially smaller than the contribution of the first filled sub-band.

Influence on ferric chloride aqueous solution caused by external electrostatic field: a molecular dynamics simulation study.

A detailed analysis of structural properties and dynamic properties of ferric chloride aqueous solution under external electrostatic fields with different intensities was performed by molecular dynamics (MD) simulations. The effects on the ferric chloride aqueous solution caused by using an electrostatic field were examined in terms of the radial distribution function of the Fe3+ ion and water molecule/Cl−, coordination number of water/Cl− around the Fe3+ ion, characteristics of hydrogen bonds, solution viscosity, and how these effects influence the hydrolysis process of the Fe3+ ion. The goal behind the study is to attain additional insights into the mechanism of electrocoagulation when ferric chloride is used as coagulant, and provide a fundamental basis for the practical use of this technology.

Asymptotic Calculation of the Intensity of Dipole Electromagnetic Radiation of an Uncharged Drop Oscillating in the Electrostatic Field

An analysis is carried out on the electromagnetic radiation of an uncharged drop oscillating in an electrostatic field using nonlinear asymptotic calculations for two small parameters (the value of a dimensionless stationary deformation of an initially spherical drop and the amplitude of its capillary oscillations). In the external electrostatic field, on the top of the drop, electric charges with the opposite signs are formed, to which the “effective” charges located on the drop’s symmetry axis are added relatively. Since the distance between those “effective” charges is about the length of the drop’s radius, they form a dipole, which at the distances much longer than the sizes of the drop creates a similar electric field as the drop itself. During the oscillation of the drop surface, the dipole will also oscillate, which will generate the electromagnetic waves of the dipole type.

Research of efficiency of application of external physical fields for sedimentation of liquid-droplets aerosols of different concentration

A theoretical estimation of extent of influence of physical and chemical properties and concentration of the weighed particles on evolution of parameters of a liquid-droplets aerosol is carried out in the work. A series of experiments on a research of parameters of aerosol media with a various structure and concentration characteristics of a dispersive phase under ex-ternal (ultrasonic and electrostatic) fields were made.

The tunneling potential for field emission from nanotips

In the quasi-planar approximation of field emission, the potential energy due to an external electrostatic field E0 is expressed as −eγE0Δs, where Δs is the perpendicular distance from the emission site and γ is the local field enhancement factor on the surface of the emitter. We show that for curved emitter tips, the current density can be accurately computed if terms involving (Δs/R2)2 and (Δs/R2)3 are incorporated in the potential where R2 is the second (smaller) principle radius of curvature. The result is established analytically for the hemiellipsoid and hyperboloid emitters, and it is found that for sharply curved emitters, the expansion coefficients are equal and coincide with that of a sphere. The expansion seems to be applicable to generic emitters as demonstrated numerically for an emitter with a conical base and quadratic tip. The correction terms in the potential are adequate for Ra⪆2 nm for local field strengths of 5 V/nm or higher. The result can also be used for nano-tipped emitter arrays or even a randomly placed bunch of sharp emitters.

Scaling laws for migrating cloud of low-Reynolds-number particles with Coulomb repulsion

We investigate the evolution of spherical clouds of charged particles that migrate under the action of a uniform external electrostatic field. Hydrodynamic interactions are modelled by Oseen equations and the Coulomb repulsion is calculated through pairwise summation. It is shown that strong long-range Coulomb repulsion can prevent the breakup of the clouds covering a wide range of particle Reynolds number $Re_{p}$ and cloud-to-particle size ratio $R_{0}/r_{p}$. A dimensionless charge parameter $\unicode[STIX]{x1D705}_{q}$ is constructed to quantify the effect of the repulsion, and a critical value $\unicode[STIX]{x1D705}_{q,t}$ is deduced, which successfully captures the transition of a cloud from hydrodynamically controlled regime to repulsion-controlled regime. Our results also reveal that, with sufficiently strong repulsion, the cloud undergoes a universal self-similar expansion. Scaling laws of cloud radius $R_{cl}$ and particle number density $n$ are obtained by solving a continuum convection equation.

TESTING OF NUMERICAL SOLUTION OF THE PROBLEM OF DETERMINING SOURCES OF MAGNETOSTATIC FIELD IN MAGNETIZED MEDIUM

Purpose. Testing of numerical solution algorithm for integral equation for calculation of plane meridian magnetostatic field source distribution at interfaces of piecewise homogeneous magnetized medium by means of electrostatic analogy. Methodology. The piecewise homogeneous medium consists of three regions with different magnetic permeabilities: the shell of arbitrary meridian section, external unlimited medium outside the shell, and the medium inside the shell. For testing external homogeneous magnetic field effect on spherical shell is considered. The analytical solution of this problem on the basis of electrostatic analogy from the solution of the problem uniform electrostatic field effect on dielectric shell is obtained. We have compared results of numerical solution of integral equation with the data obtained by means of analytical solution at the variation of magnetic permeabilities of regions of medium. Results. Integral equation and the algorithm of its numerical solution for calculation of source field distribution at the boundaries of piecewise homogeneous medium is validated. Testing of integral equations correctness for calculation of fictitious magnetic charges distribution on axisymmetric boundaries of piecewise homogeneous magnetized medium and algorithms of their numerical solutions can be carried out by means of analytical solutions of problems of homogeneous electrostatic field effect analysis on piecewise homogeneous dielectric medium with central symmetry of boundaries – single-layer and multilayer spherical shells. In the case of spherical shell in wide range of values of the parameter λk, including close to ± 1, numerical solution of integral equation is stable, and relative error in calculating of fictitious magnetic charges surface density and magnetic field intensity inside the shell is from tenths of a percent up to several percent except for the cases of very small values of these quantities. Originality. The use analytical solutions for problems of calculation of external electrostatic field effect on piecewise homogeneous dielectric bodies for testing integral equations of magnetostatics and algorithms for their numerical solutions. Practical value. The described method of testing integral equations of magnetostatics and their numerical solutions can be used for calculation of magnetic fields of spacecraft control system electromagnets.

Electric-field-mediated instability modes and Fréedericksz transition of thin nematic films

Instabilities at the deformable free surface of a thin nematic liquid crystal film can develop interesting patterns when exposed to an external electrostatic field. A general linear stability analysis is performed involving the Ericksen–Leslie governing equations for the dynamics of the nematic film coupled with the anisotropic Maxwell stresses for the electric field to uncover the salient features of these instabilities. The study reveals the coexistence of twin instability modes: (i) long-wave interfacial mode – stimulated when the sole destabilizing influence of the electric field overcomes the Frank bulk elasticity and surface tension force, and (ii) finite-wavenumber mode – engendered by the combined destabilizing influence originating from the anisotropic electric field and Ericksen stress, for the films with positive dielectric anisotropy and weaker Frank bulk elasticity. The results reported here are in contrast with the same obtained from the more frequently employed long-wave approach. The air-to-liquid-crystal filling ratio between the electrodes as well as thermodynamic parameters such as the dielectric anisotropy, Frank elasticity, and director orientations across the film and boundaries are found to play crucial roles in the selection of modes, whereas kinetic parameters such as Leslie viscosity coefficients influence only the time scale of instability. Importantly, at higher field intensities a symmetry-breaking Fréedericksz-type transition of director orientations is found to happen, which also causes the transition of the dominant mode of instability from the long-wave to the finite-wavenumber mode for films with relatively lower values of Frank bulk elasticity and positive dielectric anisotropy.