Showing papers on "Electromagnetic field published in 2014"

Periodically-driven quantum systems: Effective Hamiltonians and engineered gauge fields

Abstract: Topological effects can result from a material's intrinsic properties, or can be generated by external electromagnetic fields or mechanical deformations. Researchers analyze how driven quantum systems can lead to new topological states of matter.

Electromagnetic Theory for Microwaves and Optoelectronics

Abstract: This book is a first year graduate text on electromagnetic fields and waves. At the same time it serves as a useful reference for researchers and engineers in the areas of microwaves and optoelectronics. Following the presentation of the physical and mathematical foundations of electromagnetic theory, the book discusses the field analysis of electromagnetic waves confined in material boundaries, or so-called guided waves, electromagnetic waves in open space, scalar diffraction theory and active devices. The theories and methods presented in the book are foundations of wireless engineering, microwave and millimeter wave techniques, optoelectronics and optical fiber transmission.

Quantum electrodynamical density-functional theory: Bridging quantum optics and electronic-structure theory

Abstract: In this work, we give a comprehensive derivation of an exact and numerically feasible method to perform ab initio calculations of quantum particles interacting with a quantized electromagnetic field. We present a hierarchy of density-functional-type theories that describe the interaction of charged particles with photons and introduce the appropriate Kohn-Sham schemes. We show how the evolution of a system described by quantum electrodynamics in Coulomb gauge is uniquely determined by its initial state and two reduced quantities. These two fundamental observables, the polarization of the Dirac field and the vector potential of the photon field, can be calculated by solving two coupled, nonlinear evolution equations without the need to explicitly determine the (numerically infeasible) many-body wave function of the coupled quantum system. To find reliable approximations to the implicit functionals, we present the appropriate Kohn-Sham construction. In the nonrelativistic limit, this density-functional-type theory of quantum electrodynamics reduces to the densityfunctional reformulation of the Pauli-Fierz Hamiltonian, which is based on the current density of the electrons and the vector potential of the photonfield. By making further approximations, e.g., restricting the allowed modes of the photon field, we derive further density-functional-type theories of coupled matter-photon systems for the corresponding approximate Hamiltonians. In the limit of only two sites and one mode we deduce the appropriate effective theory for the two-site Hubbard model coupled to one photonic mode. This model system is used to illustrate the basic ideas of a density-functional reformulation in great detail and we present the exact Kohn-Sham potentials for our coupled matter-photon model system.

Guided wave couplers for coupling electromagnetic waves between a waveguide surface and a surface of a wire

Abstract: A dielectric waveguide coupling system for launching and extracting guided wave communication transmissions from a wire. At millimeter-wave frequencies, wherein the wavelength is small compared to the macroscopic size of the equipment, transmissions can propagate as guided waves guided by a strip of dielectric material. Unlike conventional waveguides, the electromagnetic field associated with the dielectric waveguide is primarily outside of the waveguide. When this dielectric waveguide strip is brought into close proximity to a wire, the guided waves decouple from the dielectric waveguide and couple to the wire, and continue to propagate as guided waves about the surface of the wire.

Lorentz invariance in chiral kinetic theory.

Abstract: A kinetic theory, with explicit Lorentz invariance, is derived for chiral fermions in an external electromagnetic field. This theory provides the correct form for the chiral vortical effect --- the appearance of a current in a system undergoing rotation.

Field induced positional shift of Bloch electrons and its dynamical implications.

Abstract: We derive the field correction to the Berry curvature of Bloch electrons, which can be traced back to a positional shift due to the interband mixing induced by external electromagnetic fields. The resulting semiclassical dynamics is accurate to second order in the fields, in the same form as before, provided that the wave packet energy is derived up to the same order. As applications, we discuss the orbital magnetoelectric polarizability and predict nonlinear anomalous Hall effects.

Electrodynamics of Axisymmetric Pulsar Magnetosphere with Electron-Positron Discharge: A Numerical Experiment

Abstract: We present the first self-consistent global simulations of pulsar magnetospheres with operating e ± discharge. We focus on the simple configuration of an aligned or anti-aligned rotator. The star is spun up from a zero (vacuum) state to a high angular velocity, and we follow the coupled evolution of its external electromagnetic field and plasma particles using the "particle-in-cell" method. A plasma magnetosphere begins to form through the extraction of particles from the star; these particles are accelerated by the rotation-induced electric field, producing curvature radiation and igniting e ± discharge. We follow the system evolution for several revolution periods, longer than required to reach a quasi-steady state. Our numerical experiment puts to test previous ideas for the plasma flow and gaps in the pulsar magnetosphere. We first consider rotators capable of producing pairs out to the light cylinder through photon-photon collisions. We find that their magnetospheres are similar to the previously obtained force-free solutions with a Y-shaped current sheet. The magnetosphere continually ejects e ± pairs and ions. Pair creation is sustained by a strong electric field along the current sheet. We observe powerful curvature and synchrotron emission from the current sheet, consistent with Fermi observations of gamma-ray pulsars. We then study pulsars that can only create pairs in the strong-field region near the neutron star, well inside the light cylinder. We find that both aligned and anti-aligned rotators relax to the "dead" state with suppressed pair creation and electric currents, regardless of the discharge voltage.

Electromagnetic Scattering by Particles and Particle Groups: An Introduction

Abstract: Preface Acknowledgements 1. Introduction 2. The macroscopic Maxwell equations and monochromatic fields 3. Fundamental homogeneous-medium solutions of the macroscopic Maxwell equations 4. Basic theory of frequency-domain electromagnetic scattering by a fixed finite object 5. Far-field scattering 6. The Foldy equations 7. The Stokes parameters 8. Poynting-Stokes tensor 9. Polychromatic electromagnetic fields 10. Polychromatic scattering by fixed and randomly changing objects 11. Measurement of electromagnetic energy flow 12. Measurement of the Stokes parameters 13. Description of far-field scattering in terms of actual optical observables 14. Electromagnetic scattering by a small random group of sparsely distributed particles 15. Statistically isotropic and mirror-symmetric random particles 16. Numerical computations and laboratory measurements of electromagnetic scattering 17. Far-field observables: qualitative and quantitative traits 18. Electromagnetic scattering by discrete random media: far field 19. Near-field scattering by a sparse discrete random medium: microphysical radiative transfer theory 20. Radiative transfer in plane-parallel particulate media 21. Weak localization 22. Epilogue Appendix A. Dyads and dyadics Appendix B. Free-space dyadic Green's function Appendix C. Euler rotation angles Appendix D. Spherical-wave expansion of a plane wave in the far zone Appendix E. Integration quadrature formulas Appendix F. Wigner d-functions Appendix G. Stationary phase evolution of a double integral Appendix H. Hints and answers to selected problems Appendix I. List of acronyms References Index.

Asymmetric Coil Sets for Wireless Stationary EV Chargers With Large Lateral Tolerance by Dominant Field Analysis

Abstract: Asymmetric coil sets for wireless stationary electric vehicle (EV) chargers, which has significantly larger lateral tolerance than previous ones, is proposed. The pick-up coil set is much smaller than the power supply coil set, thereby allowing large lateral and longitudinal displacements as well as robustness to air-gap displacement. Electromagnetic field (EMF) is reasonably reduced by arranging magnetic poles along the EV's moving direction so that alternating magnetic flux through adjacent poles cancels each other. A dominant field analysis useful for complex vector magnetic flux simulation is newly proposed, which is applicable to any resonating coils of an inductive power transfer system (IPTS). Furthermore, a hysteresis loss model is suggested, which appropriately reflects the partial core saturation on a system analysis. A prototype IPTS including the proposed coil sets were designed and successfully verified by experiments. In the quick charging mode, maximum output power of 15 kW, large lateral displacement of 40 cm, longitudinal displacement of 20 cm, air gap of 15 cm were achieved, and low EMF of 6.1 μT at 20 kHz was achieved in the normal charging mode of 5 kW.

Electromagnetic and gravitational responses of two-dimensional noninteracting electrons in a background magnetic field

Abstract: We compute electromagnetic, gravitational, and mixed linear response functions of two-dimensional free fermions in an external quantizing magnetic field at an integer filling factor. The results are presented in the form of the effective action and as an expansion of currents and stresses in wave vectors and frequencies of the probing electromagnetic and metric fields. In addition to the well-studied $U(1)$ Chern-Simons and Wen-Zee terms we find a gravitational Chern-Simons term that controls the correction to the Hall viscosity due to the background curvature. We relate the coefficient in front of the term with the chiral central charge.

Nanoscale three-dimensional reconstruction of electric and magnetic stray fields around nanowires

Abstract: Static electromagnetic stray fields around nanowires (NWs) are characteristic for a number of important physical effects such as field emission or magnetic force microscopy. Consequently, an accurate characterization of these fields is of high interest and electron holographic tomography (EHT) is unique in providing tomographic 3D reconstructions at nm spatial resolution. However, several limitations of the experimental setup and the specimen itself are influencing EHT. Here, we show how a deliberate restriction of the tomographic reconstruction to the exterior of the NWs can be used to mitigate these limitations facilitating a quantitative 3D tomographic reconstruction of static electromagnetic stray fields at the nanoscale. As an example, we reconstruct the electrostatic stray field around a GaAs-AlGaAs core shell NW and the magnetic stray field around a Co2FeGa Heusler compound NW.

Schwinger Effect in 4D de Sitter Space and Constraints on Magnetogenesis in the Early Universe

Abstract: We investigate pair creation by an electric field in four-dimensional de Sitter space. The expectation value of the induced current is computed, using the method of adiabatic regularization. Under strong electric fields the behavior of the current is similar to that in flat space, while under weak electric fields the current becomes inversely proportional to the mass squared of the charged field. Thus we find that the de Sitter space obtains a large conductivity under weak electric fields in the presence of a charged field with a tiny mass. We then apply the results to constrain electromagnetic fields in the early universe. In particular, we study cosmological scenarios for generating large-scale magnetic fields during the inflationary era. Electric fields generated along with the magnetic fields can induce sufficiently large conductivity to terminate the phase of magnetogenesis. For inflationary magnetogenesis models with a modified Maxwell kinetic term, the generated magnetic fields cannot exceed 10−30 G on Mpc scales in the present epoch, when a charged field carrying an elementary charge with mass of order the Hubble scale or smaller exists in the Lagrangian. Similar constraints from the Schwinger effect apply for other magnetogenesis mechanisms.

Magnetoelectric effects in local light-matter interactions.

Abstract: We study the generic dipole interaction of a monochromatic free-space electromagnetic field with a bi-isotropic nanoparticle or a molecule Contributions associated with the breaking of dual, P, and T symmetries are responsible for electric-magnetic asymmetry, chirality, and the nonreciprocal magnetoelectric effect, respectively We calculate absorption rates, radiation forces, and radiation torques for the nanoparticle and introduce novel field characteristics quantifying the transfer of energy, momentum, and angular momentum due to the three symmetry-breaking effects In particular, we put forward a concept of "magnetoelectric energy density," quantifying the local PT symmetry of the field Akin to the "superchiral" light suggested recently for local probing of molecular chirality, here we suggest employing complex fields for a sensitive probing of the nonreciprocal magnetoelectric effect in nanoparticles or molecules

Conservation of the spin and orbital angular momenta in electromagnetism

Abstract: We review and re-examine the description and separation of the spin and orbital angular momenta (AM) of an electromagnetic field in free space. While the spin and orbital AM of light are not separately meaningful physical quantities in orthodox quantum mechanics or classical field theory, these quantities are routinely measured and used for applications in optics. A meaningful quantum description of the spin and orbital AM of light was recently provided by several authors, which describes separately conserved and measurable integral values of these quantities. However, the electromagnetic field theory still lacks corresponding locally conserved spin and orbital AM currents. In this paper, we construct these missing spin and orbital AM densities and fluxes that satisfy the proper continuity equations. We show that these are physically measurable and conserved quantities. These are, however, not Lorentz-covariant, so only make sense in the single laboratory reference frame of the measurement probe. The fluxes we derive improve the canonical (nonconserved) spin and orbital AM fluxes, and include a ‘spin–orbit’ term that describes the spin–orbit interaction effects observed in nonparaxial optical fields. We also consider both standard and dual-symmetric versions of the electromagnetic field theory. Applying the general theory to nonparaxial optical vortex beams validates our results and allows us to discriminate between earlier approaches to the problem. Our

System wirelessly transferring power to a target device over a tested transmission pathway

Abstract: Described embodiments include a system, method, and apparatus A system includes an antenna comprising a sub-Nyquist holographic aperture configured to define selectable arbitrary complex radiofrequency electromagnetic fields on a surface of the antenna A path analysis engine tests power transmission pathways from the antenna to a target device located in an environment within a space radiateable by the antenna The environment includes a human being An optimization circuit selects responsive to the tested power transmission pathways a power transmission regime The regime includes an electromagnetic radiation pattern shaped to transfer radiofrequency electromagnetic power from the antenna to the target device without exceeding a radiation exposure limit for humans A gain definition circuit selects a complex radiofrequency electromagnetic field implementing the selected power transmission regime from the at least two selectable, complex radiofrequency electromagnetic fields An antenna controller defines the selected arbitrary complex radiofrequency electromagnetic field in the sub-Nyquist holographic aperture

Integrated Photonic Electromagnetic Field Sensor Based on Broadband Bowtie Antenna Coupled Silicon Organic Hybrid Modulator

Abstract: We present the design, fabrication and characterization of a compact and highly sensitive integrated photonic electromagnetic field sensor based on a silicon-organic hybrid modulator driven by a bowtie antenna. Slow-light effects in the electro-optic (EO) polymer refilled silicon slot photonic crystal waveguide (PCW), together with broadband electric field enhancement provided by the bowtie antenna, are utilized to enhance the interaction of microwaves and optical waves, enabling an ultra large effective in-device EO coefficient over 1000 pm/V and thus a high sensitivity. The EO polymer refilled slot PCW is designed for low-dispersion slow-light propagation, high poling efficiency, and high optical mode confinement inside the slot. The bowtie antenna acts not only as a receiving antenna, but also as poling electrodes during the fabrication process. A bowtie antenna integrated on doped silicon slot PCW is demonstrated to have a broad operational bandwidth, with a maximum resonance at the frequency of 10 GHz. The strongly enhanced broadband electric field is used to directly modulate the phase of the optical waves propagating through the slot PCW embedded inside the feed gap of the bowtie antenna. The phase modulation is then converted to intensity modulation using an external reference arm to form a Mach-Zehnder interferometer in our experimental setup. The sensing of electromagnetic field at 8.4 GHz is experimentally demonstrated, with a minimum detectable electromagnetic power density of $8.4\, {\rm mW\!/\!m}^{2}$ , corresponding to a minimum detectable electric field of 2.5 V/m.

Charged anisotropic models for quark stars

Abstract: We perform a detailed physical analysis for a class of exact solutions for the Einstein–Maxwell equations. The linear equation of state consistent with quark stars has been incorporated in the model. The physical analysis of the exact solutions is performed by considering the charged anisotropic stars for the particular nonsingular exact model obtained by Maharaj, Sunzu and Ray. In performing such an analysis we regain masses obtained by previous researchers for isotropic and anisotropic matter. It is also indicated that other masses and radii may be generated which are in acceptable ranges consistent with observed values of stellar objects. A study of the mass-radius relation indicates the effect of the electromagnetic field and anisotropy on the mass of the relativistic star.

Anisotropic shear viscosity of a strongly coupled non-Abelian plasma from magnetic branes

Abstract: Recent estimates for the electromagnetic fields produced in the early stages of non-central ultrarelativistic heavy ion collisions indicate the presence of magnetic fields BO (0:1 15m 2 ), where m is the pion mass. It is then of special interest to study the eects of strong (Abelian) magnetic fields on the transport coecients of strongly coupled non-Abelian plasmas, such as the quark-gluon plasma formed in heavy ion collisions. In this work we study the anisotropy in the shear viscosity induced by an external magnetic field in a strongly coupledN = 4 SYM plasma. Due to the spatial anisotropy created by the magnetic field, the most general viscosity tensor of a magnetized plasma has 5 shear viscosity coecients and 2 bulk viscosities. We use the holographic correspondence to evaluate two of the shear viscosities, ? xyxy (perpendicular to the magnetic field) and k xzxz = yzyz (parallel to the field). When B6 0 the shear viscosity perpendicular to the field saturates the viscosity bound ?=s = 1=(4 ) while in the direction parallel to the field the bound is violated since k=s < 1=(4 ). However, the violation of the bound in the case of strongly coupled SYM is minimal even for the largest value of B that can be reached in heavy ion collisions.

Surface Plasmon Resonance of Nanoparticles and Applications in Imaging

Abstract: In this paper we provide a mathematical framework for localized plasmon resonance of nanoparticles. Using layer potential techniques associated with the full Maxwell equations, we derive small-volume expansions for the electromagnetic fields, which are uniformly valid with respect to the nanoparticle's bulk electron relaxation rate. Then, we discuss the scattering and absorption enhancements by plasmon resonant nanoparticles. We study both the cases of a single and multiple nanoparticles. We present numerical simulations of the localized surface plasmonic resonances associated to multiple particles in terms of their separation distance.

Observation and Interpretation of Motional Sideband Asymmetry in a Quantum Electromechanical Device

Abstract: Quantum electromechanical systems offer a unique opportunity to probe quantum noise properties in macroscopic devices, properties that ultimately stem from Heisenberg’s uncertainty relations. A simple example of this behavior is expected to occur in a microwave parametric transducer, where mechanical motion generates motional sidebands corresponding to the up-and-down frequency conversion of microwave photons. Because of quantum vacuum noise, the rates of these processes are expected to be unequal. We measure this fundamental imbalance in a microwave transducer coupled to a radio-frequency mechanical mode, cooled near the ground state of motion. We also discuss the subtle origin of this imbalance: depending on the measurement scheme, the imbalance is most naturally attributed to the quantum fluctuations of either the mechanical mode or of the electromagnetic field.

Observations of kinetic scale field line resonances

Abstract: We identify electromagnetic field variations from the Van Allen Probes which have the properties of Doppler shifted kinetic scale Alfvenic field line resonances. These variations are observed during injections of energetic plasmas into the inner magnetosphere. These waves have scale sizes perpendicular to the magnetic field which are determined to be of the order of an ion gyro-radius (ρi) and less. Cross-spectral analysis of the electric and magnetic fields reveals phase transitions at frequencies correlated with enhancements and depressions in the ratio of the electric and magnetic fields. Modeling shows that these observations are consistent with the excitation of field-line resonances over a broad range of wave numbers perpendicular to the magnetic field (k⊥) extending to k⊥ρi ≫ 1. The amplitude of these waves is such that E/Bo ≳ Ωi/k⊥ (E, Bo, and Ωi are the wave amplitude, background field strength, and ion gyro-frequency, respectively) leading to ion demagnetization and acceleration for multiple transitions through the wave potential.

Influence of electric, magnetic, and electromagnetic fields on the circadian system: current stage of knowledge.

Abstract: One of the side effects of each electrical device work is the electromagnetic field generated near its workplace. All organisms, including humans, are exposed daily to the influence of different types of this field, characterized by various physical parameters. Therefore, it is important to accurately determine the effects of an electromagnetic field on the physiological and pathological processes occurring in cells, tissues, and organs. Numerous epidemiological and experimental data suggest that the extremely low frequency magnetic field generated by electrical transmission lines and electrically powered devices and the high frequencies electromagnetic radiation emitted by electronic devices have a potentially negative impact on the circadian system. On the other hand, several studies have found no influence of these fields on chronobiological parameters. According to the current state of knowledge, some previously proposed hypotheses, including one concerning the key role of melatonin secretion disruption in pathogenesis of electromagnetic field induced diseases, need to be revised. This paper reviews the data on the effect of electric, magnetic, and electromagnetic fields on melatonin and cortisol rhythms—two major markers of the circadian system as well as on sleep. It also provides the basic information about the nature, classification, parameters, and sources of these fields.

Out-of-equilibrium charge dynamics in a hybrid circuit quantum electrodynamics architecture

Abstract: The recent development of hybrid circuit quantum electrodynamics allows one to study how cavity photons interact with a system driven out of equilibrium by fermionic reservoirs. We study here one of the simplest combination: a double quantum dot coupled to a single mode of the electromagnetic field. We are able to couple resonantly the charge levels of a carbon-nanotube-based double dot to cavity photons. We perform a microwave readout of the charge states of this system, which allows us to unveil features of the out-of-equilibrium charge dynamics, otherwise invisible in the DC current. We extract the relaxation rate, dephasing rate, and photon number of the hybrid system using a theory based on a master equation technique. These findings open the path for manipulating other degrees of freedom, e.g., the spin and/or the valley in nanotube-based double dots using microwave light.

Methods and apparatus for optically detecting magnetic resonance

Abstract: A light-trapping geometry enhances the sensitivity of strain, temperature, and/or electromagnetic field measurements using nitrogen vacancies in bulk diamond, which have exterior dimensions on the order of millimeters. In an example light-trapping geometry, a laser beam enters the bulk diamond, which may be at room temperature, through a facet or notch. The beam propagates along a path inside the bulk diamond that includes many total internal reflections off the diamond's surfaces. The NVs inside the bulk diamonds absorb the beam as it propagates. Photodetectors measure the transmitted beam or fluorescence emitted by the NVs. The resulting transmission or emission spectrum represents the NVs' quantum mechanical states, which in turn vary with temperature, magnetic field strength, electric field strength, strain/pressure, etc.

A Green's function formalism of energy and momentum transfer in fluctuational electrodynamics

Abstract: Radiative energy and momentum transfer due to fluctuations of electromagnetic fields arising due to temperature difference between objects is described in terms of the cross-spectral densities of the electromagnetic fields. We derive relations between thermal non-equilibrium contributions to energy and momentum transfer and surface integrals of tangential components of the dyadic Green's functions of the vector Helmholtz equation. The expressions derived here are applicable to objects of arbitrary shapes, dielectric functions, as well as magnetic permeabilities. For the case of radiative transfer, we derive expressions for the generalized transmissivity and generalized conductance that are shown to obey reciprocity and agree with theory of black body radiative transfer in the appropriate limit.

Observation and interpretation of motional sideband asymmetry in a quantum electro-mechanical device

Abstract: Quantum electro-mechanical systems offer a unique opportunity to probe quantum noise properties in macroscopic devices, properties which ultimately stem from the Heisenberg Uncertainty Principle. A simple example of this is expected to occur in a microwave parametric transducer, where mechanical motion generates motional sidebands corresponding to the up and down frequency-conversion of microwave photons. Due to quantum vacuum noise, the rates of these processes are expected to be unequal. We measure this fundamental imbalance in a microwave transducer coupled to a radio-frequency mechanical mode, cooled near the ground state of motion. We also discuss the subtle origin of this imbalance: depending on the measurement scheme, the imbalance is most naturally attributed to the quantum fluctuations of either the mechanical mode or of the electromagnetic field.