Coulomb Electric Field Research Articles

Dependence of electronic properties on Coulomb repulsion and electric field in single layer FeI2

The Coulomb repulsion was applied in the framework of LDA+U approach and electric field to find out the electronic properties of a single layer 1T-FeI2. This calculation relies on the density functional theory of non-collinear magnetic structure. From the curve of energy dispersion, increasing the Coulomb parameter and electric field yields an electronic transition from a metallic state to an insulating state. This only holds in case the spin-orbit coupling is incorporated. While the magnetism still holds as the Coulomb parameter is tuned, the magnetism vanishes as the electric field is included. However, as the magnetism disappears, the spin splitting appears when increasing the electric field. This indicates that the Coulomb repulsion and electric field give a prominent impact on the electronic properties in the single layer FeI2 as the spin-orbit coupling is included.

Quantum Spatial Search with Electric Potential: Long-Time Dynamics and Robustness to Noise.

We present various results on the scheme introduced in a previous work, which is a quantum spatial-search algorithm on a two-dimensional (2D) square spatial grid, realized with a 2D Dirac discrete-time quantum walk (DQW) coupled to a Coulomb electric field centered on the the node to be found. In such a walk, the electric term acts as the oracle of the algorithm, and the free walk (i.e., without electric term) acts as the "diffusion" part, as it is called in Grover's algorithm. The results are the following. First, we run long time simulations of this electric Dirac DQW, and observe that there is a second localization peak around the node marked by the oracle, reached in a time O(N), where N is the number of nodes of the 2D grid, with a localization probability scaling as O(1/lnN). This matches the state-of-the-art 2D-DQW search algorithms before amplitude amplification We then study the effect of adding noise on the Coulomb potential, and observe that the walk, especially the second localization peak, is highly robust to spatial noise, more modestly robust to spatiotemporal noise, and that the first localization peak is even highly robust to spatiotemporal noise.

Dirac Spatial Search with Electric Fields.

Electric Dirac quantum walks, which are a discretisation of the Dirac equation for a spinor coupled to an electric field, are revisited in order to perform spatial searches. The Coulomb electric field of a point charge is used as a non local oracle to perform a spatial search on a 2D grid of N points. As other quantum walks proposed for spatial search, these walks localise partially on the charge after a finite period of time. However, contrary to other walks, this localisation time scales as for small values of N and tends asymptotically to a constant for larger Ns, thus offering a speed-up over conventional methods.

Relativistic Rotating Electromagnetic Fields

In this work, we consider axially symmetric stationary electromagnetic fields in the framework of special relativity. These fields have an angular momentum density in the reference frame at rest with respect to the axis of symmetry; their Poynting vector form closed integral lines around the symmetry axis. In order to describe the state of motion of the electromagnetic field, two sets of observers are introduced: the inertial set, whose members are at rest with the symmetry axis; and the noninertial set, whose members are rotating around the symmetry axis. The rotating observers measure no Poynting vector, and they are considered as comoving with the electromagnetic field. Using explicit calculations in the covariant 3 + 1 splitting formalism, the velocity field of the rotating observers is determined and interpreted as that of the electromagnetic field. The considerations of the rotating observers split in two cases, for pure fields and impure fields, respectively. Moreover, in each case, each family of rotating observers splits in two subcases, due to regions where the electromagnetic field rotates with the speed of light. These regions are generalizations of the light cylinders found around magnetized neutron stars. In both cases, we give the explicit expressions for the corresponding velocity fields. Several examples of relevance in astrophysics and cosmology are presented, such as the rotating point magnetic dipoles and a superposition of a Coulomb electric field with the field of a point magnetic dipole.

Search for extreme electromagnetic fields through measurements of charm mesons flow harmonics in PbPb collisions at 5.02 TeV with the CMS detector

In ultrarelativistic heavy-ion collisions, a very strong (on the order of 1016 T) and transient (lifetime on the order of 10−1 fm/c) electromagnetic (EM) field is expected to be generated inside the medium formed in the collision. This EM field, generated by the collision participants and spectators, is predicted to produce a difference in the νn harmonics for positive-and negative-charged particles, with the magnetic field mainly responsible for a splitting in rapidity-odd directed flow (ν1), and the Coulomb electric field leading to a charge-dependent splitting in the ν2 and average pT values of emitted particles. Due to the large mass, charm quarks are expected to be created very early in the collision, and thus have more chance of interacting with this strong EM field than light flavor hadrons. In this contribution, measurements of D0 (u‾c) and D‾0uc‾) mesons flow harmonics (ν2 and ν3) are presented as functions of rapidity (y), transverse momentum, and collision centrality for PbPb collisions at 5.02 TeV, using the large data samples collected by the CMS experiment during the LHC Run 2. The wide rapidity coverage (|y| < 2) of these new charm mesons measurements allow for a better understanding of the 3-dimensional evolution of the medium formed in heavy-ion collisions.

THE MODIFICATION AND DEVELOPMENT OF THE SPECTROSCOPIC PROPERTIES OF Cs/PVA BLEND INCORPORATED GOLD NANOPARTICLES (AuNPs) PREPARED BY PULSED LASER ABLATION IN LIQUIDS (PLAL)

In the present work, pure gold nanoparticles (AuNPs) were synthesis by pulsed laser ablation technique using Nd:YAG as a source of laser. Then, the prepared AuNPs was used with low concentrations to synthesis nanocomposite films by adding it to chitosan/polyvinyl alcohol (Cs/PVA) blend using the casting method. All peaks of pure AuNPs were recorded by X-ray diffraction with face center cubic (FCC) structure. No peaks of AuNPs were found at low concentrations in the doped nanocomposites because of the complete degradation of AuNPs within Cs/PVA matrix. The intensity of some IR bands was changed due to the chemical interaction between the components. The broad band at 3350 cm−1 was decreased due to the intermolecular interaction. Dielectric constant and dielectric loss were decreased as an increase in the frequency and temperature. The increases of direct conductivity (σdc) imply that the free charge density or of the charge mobility that results. The AuNPs addition assists the charge transfer complex (CTCs) formation in which charge transportation occurs by coulomb forces and electric field. The Cole-Cole plot shows semicircles that supports the relaxation processes were a non‐ Debye method.

Plunging in the Dirac sea using graphene quantum dots

The dynamics of low energy charge carriers in a graphene quantum dot subjected to a time-dependent local field is investigated numerically. In particular, we study a configuration where a Coulomb electric field is provided by an ion traversing the graphene sample. A Galerkin-like numerical scheme is introduced to solve the massless Dirac equation describing charge carriers subjected to space- and time-dependent electromagnetic potentials and is used to evaluate the field induced interband transitions. It is demonstrated that as the ion goes through graphene, electron-hole pairs are generated dynamically via the adiabatic pair creation mechanism around avoided crossings, similar to electron-positron pair generation in low energy heavy ion collisions.

Surface charges from a sensing pixel perspective

A new technique is presented for understanding how charges distribute themselves on the surface of a conductor during current flow. The technique uses a set of three-dimensional calculation cells (“pixels”) that cover the conductor's surface and contain internal charge. The pixels have two faces separated by an infinitesimal, but finite, distance, with one face being conductive and the other non-conductive. Each pixel acts as a sensor by responding to (“sensing”) the net Coulomb electric field at its conductive face due to charges in other pixels and charges at the current source and sink (collectively, the external charges). Through a feedback process implemented as a series of time steps, the pixels' internal charges adjust themselves until, at each pixel, a balance is achieved between the electric flux at the conductive face due to the external charges and that due to the pixel's internal charge. Specifically, at each time step, for each pixel at which there is flux imbalance, charge will move into or out of the pixel's conductive face in the direction that reduces the imbalance. The charge distribution for the set of pixels that gives balanced flux for each of the pixels is the system's steady state and for systems where retardation effects are not significant, e.g., biological systems, the time series is the path by which the system reaches that state. Fluxes are calculated using solid angles and because solid angles do not vary with a change in scale, the charge distribution, when expressed in terms of charges/pixel, as opposed to charges/area, depends only on the system shape.

CHERENKOV RADIATION OF THE ELECTRON BUNCH IN DIELECTRIC MEDIA WITH FREQUENCY DISPERSION

Excitation of the Cherenkov electromagnetic radiation by a relativistic electron bunch in a dielectric waveguide is considered taking into account the frequency dispersion of the dielectric permittivity. Electric polarization in an isotropic dielectric medium and, accordingly, polarization charges and currents induced by the Coulomb electric field of a relativistic electron bunch are determined. The spatial-temporal structure of the excited wakefield in a dielectric waveguide is obtained and investigated. It is shown that the excited field consists of a potential polarization electric field and a set of eigen electromagnetic waves of the dielectric waveguide.

Electro-optic sampling of optical pulses and electron bunches for a compact THz-FEL source

A systematic one dimensional analytical model describing the full electromagnetic propagation in electro-optic (EO) diagnostic is proposed and designed for a terahertz FEL source at HUST. Our model contains two main aspects: the propagation of the THz pulse (1.5–6 THz) along the transport line and the THz EO process in the detection crystal. The diffraction, Fabry–Perot and focusing effects are included in the THz propagation process. The phase mismatch, the frequency-dependent EO coupling coefficient and geometrical overlap between probe and THz pulses as well as the group velocity dispersion and finite duration of the probe pulse are considered in the THz EO process. The calculation shows that the diffraction in the TPX window and the Fabry–Perot effect in the GaP crystal are crucial for retrieving the details of the THz optical pulse. While for electron bunches, the detected Coulomb electric field will be significantly broadened due to the relatively low relativistic Lorenz factor (γ=10–20). Therefore, a convenient deconvolution algorithm is utilized to reconstruct THz electric field from the distorted EO signals, where the truncated singular value decomposition method is employed. Our algorithm is verified to work well even with a low signal-to-noise ratio (20 dB) in the future measurement.

Thermodynamics of charged dilatonic BTZ black holes in rainbow gravity

In this paper, the charged three-dimensional Einstein's theory coupled to a dilatonic field has been considered in the rainbow gravity. The dilatonic potential has been written as the linear combination of two Liouville-type potentials. Four new classes of charged dilatonic rainbow black hole solutions, as the exact solution to the coupled field equations of the energy dependent space time, have been obtained. Two of them are correspond to the Coulomb's electric field and the others are consequences of a modified Coulomb's law. Total charge and mass as well as the entropy, temperature and electric potential of the new charged black holes have been calculated in the presence of rainbow functions. Although the thermodynamic quantities are affected by the rainbow functions, it has been found that the first law of black hole thermodynamics is still valid for all of the new black hole solutions. At the final stage, making use of the canonical ensemble method and regarding the black hole heat capacity, the thermal stability or phase transition of the new rainbow black hole solutions have been analyzed.

Time-Varying Seismogenic Coulomb Electric Fields as a Probable Source for Pre-Earthquake Variation in the Ionospheric F2-Layer

The electric coupling between the lithosphere and the ionosphere is examined. The electric field is considered as a timevarying irregular vertical Coulomb field presumably produced on the Earth’s surface before an earthquake within its epicentral zone by some micro-processes in the lithosphere. It is shown that the Fourier component of this electric field with a frequency of 500 Hz and a horizontal scale-size of 100 km produces in the nighttime ionosphere of high and middle latitudes a transverse electric field with a magnitude of ~20 mV/m if the peak value of the amplitude of this Fourier component is just 30 V/m. The time-varying vertical Coulomb field with a frequency of 500 Hz penetrates from the ground into the ionosphere by a factor of ~7×105 more efficient than a time independent vertical electrostatic field of the same scale size. The transverse electric field with amplitude of 20 mV/m will cause perturbations in the nighttime F region electron density through heating the F region plasma resulting in a reduction of the downward plasma flux from the protonosphere and an excitation of acoustic gravity waves.

Coulomb flux tube on the lattice

In Coulomb gauge a longitudinal electric field is generated instantaneously with the creation of a static quark-antiquark pair. The field due to the quarks is a sum of two contributions, one from the quark and one from the antiquark, and there is no obvious reason that this sum should fall off exponentially with distance from the sources. We show here, however, from numerical simulations in pure SU(2) lattice gauge theory, that the color Coulomb electric field does in fact fall off exponentially with transverse distance away from a line joining static quark-antiquark sources, indicating the existence of a color Coulomb flux tube, and the absence of long-range Coulomb dipole fields.

Single-shot electro-optic experiments for electron bunch diagnostics at Tsinghua Accelerator Laboratory

The electro-optic (EO) technique detects the Coulomb electric field distribution of relativistic electron bunches to obtain the associated longitudinal profile. This diagnostic method allows the direct time-resolved single-shot measurement and thus the real-time monitoring of the bunch profile and beam arrival time in a non-destructive way with sub-picosecond temporal resolution. In this paper, we report the measurement of the longitudinal profile of an electron bunch through electro-optic spectral decoding detection, in which the bunch profile is encoded into the spectra of the linearly chirped laser pulse. The experimental setup and measurement results of a 40MeV electron bunch are presented, with a temporal profile length of 527fs rms (~1.24ps FWHM) and a beam arrival time jitter of 471fs rms. Temporal resolution and future experimental improvement are also discussed.

Initial spatial distribution of geminate charge carriers photogenerated in doped conjugated polymers

A diffusion model of the charge carrier photogeneration in doped conjugated polymers is suggested. A dissociation of a vibrationally relaxed exciton into a Coulombically bound geminate pair of charges occurs at a charge transfer center which consists of a conjugated segment of a polymer chain and a nearby dopant molecule. A photogenerated hole executes one-dimensional diffusion motion along the conjugated segment in the on-chain potential well formed by the Coulomb and external electric fields. Holes are assumed to become localized in trapping sites. It is shown that the spatial distribution of trapped holes is determined mainly by effective temperature of pretrapped holes and external electric field. The model is consistent with experimental data on photoconduction of a copolymer of a phenyl-substituted poly-phenylenevinylene doped with trinitrofluorenone, which have been reported by Weiter et al. (2004). Effective temperature of holes is evaluated at about 1200K.

Physics Teaching: Mathematics as an Epistemological Tool

We study the interconnection between Physics and Mathematics in concrete instances, departing from the usual expression for the Coulomb electric field, produced by a point-like charge. It is scrutinized by means of six epistemology-intensive questions and radical answers are proposed, intended to widen one’s understanding of the subject. Our interventions act along two complementary directions. One of them regards ontology, since questions induce one to look closely at the electric charge, from different perspectives, promoting reflections about its nature and reinforcing the corresponding concept. Formal manipulations rely on the identification of concepts with symbols, and the other direction concerns the spatial extension of mathematical structures. Our questions and their somewhat unusual answers help disclosing information which is not present in many textbooks, and show that Mathematics can be used as an efficient epistemological tool in Physics teaching.

Role of e–e repulsion interaction in nonsequential double ionization of Xe by linearly and elliptically polarized laser pulses

We investigated the nonsequential double ionization (NSDI) of Xe by linearly polarized (LP) and elliptically polarized (EP) laser pulses using the classical ensemble model. For the two cases, the ensemble from NSDI was separated into two kinds of subensemble according to the relative momentum along the y-axis [Formula: see text], respectively. The results show only for the case of relatively small [Formula: see text], the momentum distribution along the x-axis can show a V-like shape obviously, which is according with the experiment [Phys. Rev. Lett.99, 263003 (2007)]. What is important is that we firstly examine the role of the repulsion interaction between two electrons for the two kinds of subensemble, and find that the process of NSDI for the case of relatively small [Formula: see text] exits a strong repulsion interaction which contributes significantly to the V-like shape. However, for the case of relatively big [Formula: see text], the repulsion interaction between two electrons is relatively weak, and both the nuclear Coulomb attraction and electric field force dominate the process of NSDI.

The Quantum Oscillatory Modulated Potential—Electric Field Wave Packets Produced by Electrons

In this work we are formulating a new theory for describing the waving nature of a microscopic electric particle. Based on the predictions of the Quantum Oscillatory Modulated Potential—QOMP, for describing the interaction between two microscopic electric particles, electron-electron, for instance, we are postulating that the waving behavior of these particles may be an attribute of the charges of the particles and not their masses as currently accepted. For a microscopic electric charge, we are presenting new arguments showing that the electric field in the vicinity of a microscopic charge is spatially waving and can be determined as the gradient per unit of charge of this new quantum interaction potential, with use of an appropriated phase factor to account for the behavior of an unbound electron. Differently of what is predicted by the classical Coulomb electric field, when a charged particle is moving under the action of a potential of V volts, the new electric field existing around the charge has the form of a wave packet. For typical values of the potential V, the wavelength of the waving electric field is in very good agreement with those experimentally observed with diffraction of electrons in crystalline solids.

Photogeneration of charge carriers in a weakly disordered π-conjugated polymer at high photon energies of exciting light

Model of photoionization of a weakly disordered conjugated polymer is proposed for high photon energies of exciting light. The vibrational energy of photogenerated excitons is assumed to go into heating of a conjugated segment. This results in an increase of temperature of mobile charges produced by dissociation of excitons. The vibrational heating of the conjugated segment is assumed to be conserved for so long that charge carriers can cross the potential barrier formed by the Coulomb and external electric fields during their diffusion motion along the excited segment with effective temperature Teff. It is shown that the model agrees with experimental data on photocarrier quantum yield in films of a methyl-substituted ladder-type poly-para-phenylene (MeLPPP) obtained by Bath et al. [Chem. Phys. Lett. 288 (1998) 147–154]. The effective temperature Teff>1200K is estimated in MeLPPP for wavelength 250nm.

Nonlinear corrections in basic problems of electro- and magneto-statics in the vacuum

We point that any theoretically found value for an electromagnetic multipole of a baryon or a meson should be subjected to ``renormalization'' due to nonlinearity of QED. We find third-power nonlinear corrections to the Coulomb and other static electric fields, as well as to the electric and magnetic dipole fields, as we work within QED with no background field. The nonlinear response function on which we base our consideration is the fourth-rank polarization tensor, calculated within the local (infrared) approximation of the effective action, the results being applicable to weakly varying and not too strong fields. It is established that the nonlinear corrections to magnetic moments of some baryons and mesons, fitting the present approximate scheme, match the existing indeterminacy in their theoretical values.