Dynamic electron transport theory for multiprobe mesoscopic structures

Using the linear response theory and random phase approximation,we develop a general dynamic electron transport theory for multiprobe mesoscopic structures in an arbitrarily time-dependent external field.In this case,the responses of the dynamic current,charge and internal potential to the external fields can be determined self-consistently.Without loss of generality,charge (current) conservation and gauge invariance under a potential shift are satisfied.As an example,we employ a quantum wire with a single barrier to discuss the response of the internal potential.     

Electromagnetic Parameters Model and Microwave Absorption for Composite Coatings Containing Magnetic Particles

Considering the eddy current effect of the magnetic metal particles in a high frequency electromagnetic field, we extend the Maxwell-Garnett law by introducing the eddy-effect parameter A which is as functions of the radius, permeability and electric conductivity of the metal particle medium. It is obvious that the computational result agrees with the experiment, which indicates that the extended Maxwell-Garnett law can be used to predict the effective electromagnetic parameters of a dilute metal-insulator composite medium in a high-frequency electromagnetic field.     

Electromagnetically induced transparency in novel dual-band metamaterial excited by toroidal dipolar response

We demonstrated a novel metamaterial with dual-band electromagnetically induced transparency(EIT)via simulation,experiment and numerical analysis,with resonance frequencies of the trans-parency peaks of 7.60 and 10.27 GHz.The E-εmetamaterial unit cells were composed of E-shaped and e-shaped patterns.By analyzing the surface current distribution and the magnetic field,we qualitatively verified the toroidal dipole response in the E-εmetamaterial at 10.27 GHz.Meanwhile,by calculating the multipole's radiated power,we found that the two transparency peaks were due to the excitation of the electric and toroidal dipole responses.By changing the incident angle from 0°to 60°,we observed changes in transmission spectra,and the quality factors(Q-factors)of the two transparency peaks increased.In addition,the proposed E-εmetamaterial can be designed to act as a refractive index sensor or other electronic equipment for the control of electromagnetic waves.     

Hawking Radiation of Dirac Field in the Linear Dilaton Black Hole

By studying the perturbation of massless Dirac field in the background of linear dilaton black hole we show that the covariant Dirac equation can be separated into radial and angular equations. The Damour-Ruffini method is applied to derive the spectrum of Hawking radiation for the Dirac field, from which the Hawking temperature can be read off. It is shown that the Hawking temperature is consistent with the result calculated from the surface gravity.     

Time dependence of the average charge and current in a dissipative mesoscopic circuit

Taking into consideration the interactions between electrons and phonons,we have studied the temporal evolution of the average charge and current in a dissipative mesoscopic RLC circuit.Our results show that a mesoscopic RLC circuit can be treated as an interactive system between an electromagnetic harmonic oscillator and many lattice harmonic oscillators;this is called the bathing of the harmonic oscillators.The results also show that the quantum equation of motion of the linear mesoscopic RLC circuit is identical in form to its classical equation of motion,the only difference between them being their respective meanings.In order to thoroughly study the quantum properties of a dissipative mesoscopic circuit,we have to consider not only the electromagnetic energy of the circuit,but also the crystal lattice vibration energy and the interactive energy between electrons and phonons.     

Deposition of ZnO Films on Freestanding CVD Thick Diamond Films

For ZnO/diamond structured surface acoustic wave （SAW） filters, performance is sensitively dependent on the quality of the ZnO films. In this paper, we prepare highly-oriented and fine grained polycrystalline ZnO thin films with excellent surface smoothness on the smooth nucleation surfaces of freestanding CVD diamond films by metal organic chemical vapour deposition （MOCVD）. The properties of the ZnO films are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, and photoluminescence （PL） spectrum. The influences of the deposition conditions on the quality of ZnO films are discussed briefly. ZnO/freestanding thick-diamond-film layered SAW devices with high response frequencies are expected to be developed.     

Thin film micro-scaled cold cathode structures of undoped and Si-doped AlN grown on SiC substrate with low turn-on voltage

The field emission characteristics of the AlN thin films with micro-scaled cold cathode structures are tested in the high vacuum system. The aluminum nitride(AlN) thin films with a thickness of about 100 nm are prepared on the n-type 6H-SiC(0001) substrate at 1100°C by metal organic chemical vapor deposition(MOCVD) under low pressure. The I–V curves and surface micro-images of undoped and Si-doped AlN films are investigated. From the I–V and Fowler–Nordheim plots,it can be seen that the Si-doped Al N shows better field emission characteristics compared with the undoped AlN sample.The obtained turn-on field is 6.7 V/μm and the maximum emission current density is 154 m A/cm2 at 69.3 V for the Sidoped AlN film cathode after proper surface treatment. It is proposed that the relatively low electric resistivity of Si-doped Al N films is significant for electron migration to the surface region, and their rougher surface morphology is beneficial to a higher local electric field enhancement for the field emission.     

Effective Dielectric Properties of Au-ZnS and Au-ZnO Plasmonics Nanocomposites in the Terahertz Regime

Composite materials based on plasmonic nanoparticles allow building metamaterials with very large effective permittivity （positive or negative）. Moreover, if clustered or combined with other nanoparticles, it is also possible to generate effective magnetic permeability （positive or negative）, and an ad-hoc design would result in the generation of double negative materials, and therefore backward wave propagation. In this work, the optical properties such as the effective permittivity, permeability and refractive index of Au-ZnS and Au-ZnO nanocomposites in a broad frequency range are studied. The enhancement is attributed to energy transfer from ZnS or ZnO to Au followed by a large local electromagnetic field on or near the surface of the Au nanoparticles. Local surface plasmon resonance could be the key＂ reason for this enhancement. The surface plasmon, in response to changes in the refractive index of the local environment, also depends on the type of metal through the bulk plasma wavelength and the nano-particle compositions and geometry.     

Influence of External Magnetic Field on Anomalous Skin Effects in Inductively Coupled Plasmas

Using a one-dimensional slab model, we study the influence of the external static magnetic field on the anomalous skin effects in the inductively coupled plasma. The rf electromagnetic field in the plasma is determined by solving the linearized Boltzmann equation incorporating with the Maxwell equations. The numerical results show that,due to the existence of the external magnetic field, the anomalous skin effects are greatly enhanced and the number of regions with negative absorption is decreased.     

On the connection between the solutions to the Dirac and Weyl equations and the corresponding electromagnetic four-potentials

In this work we study in detail the connection between the solutions to the Dirac and Weyl equations and the associated electromagnetic four-potentials.First,it is proven that all solutions to the Weyl equation are degenerate,in the sense that they correspond to an infinite number of electromagnetic four-potentials.As far as the solutions to the Dirac equation are concerned,it is shown that they can be classified into two classes.The elements of the first class correspond to one and only one four-potential,and are called non-degenerate Dirac solutions.On the other hand,the elements of the second class correspond to an infinite number of four-potentials,and are called degenerate Dirac solutions.Further,it is proven that at least two of these fourpotentials are gauge-inequivalent,corresponding to different electromagnetic fields.In order to illustrate this particularly important result we have studied the degenerate solutions to the forcefree Dirac equation and shown that they correspond to massless particles.We have also provided explicit examples regarding solutions to the force-free Weyl equation and the Weyl equation for a constant magnetic field.In all cases we have calculated the infinite number of different electromagnetic fields corresponding to these solutions.Finally,we have discussed potential applications of our results in cosmology,materials science and nanoelectronics.     

Surface plasmon-polaritons wave fields in the vicinity of a metallic nanohole

It is shown that metal surface with a nanohole can support surface plasmon-polaritons (SPP), whose wave fields are described by Hankel functions. These plasmons can be excited by an electromagnetic wave incident at the metal surface. The optical transmission through subwavelength holes in metal films can essentially be enhanced by interaction of the incident light with surface plasmons. Dependence of excitation of the wave field of SPP on the incidence angle and on the wavelength of incident light is considered.     

等离子体金属波导在外磁场调制下的传输模式

在通信系统中波导的设计向着多功能和可调制方向发展。波导基于等离子体金属材料在外磁场作用下设计平面波导。等离子体金属材料在外磁场作用下会产生表面等离子体激元和非互易传播双重功能。从基本的麦克斯韦方程和边界条件出发,详细推导了模式的色散方程,并根据模式特征进行了分类。波导具有明显的非互易传播和可调制的特性。     

Polarization properties of porous gold and silver films

Using the method of polarization modulation of electromagnetic radiation and the Kretschmann geometry, we perform comparative studies of surface plasmon resonance in porous and continuous gold and silver films. The spectral dependences of the polarization difference of the reflection coefficients of nano-composites are obtained for the first time and are supplemented by angular characteristics of this parameter. We show that these dependences characterize particular features of the optical properties related to the structure, morphology, and topology of porous films. We reveal that surface plasmon-polaritons and local plasmons in porous films can be excited both by radiation that is p polarized with respect to the plane of incidence, as is the case with continuous films, and by s polarized radiation. We demonstrate that the measurement results can yield information on the structural properties of films, such as their thickness, roughness height, degree of dispersion of nanoparticles, and so on.     

Plasmonic enhancement of linear birefringence and linear dichroism in anisotropic optical metamaterials

The resonant behavior of linear birefringence and linear dichroism spectra is found in anisotropic optical metamaterials made of noble metal thin films with stripes and rectangular hole nanoapertures forming one- or two-dimensional subwavelength gratings. Differences in effective refractive index and extinction coefficient for linearly polarized eigenstates are increased in spectral range of resonances of local and surface plasmon-polaritons at the normal incidence and reach the values of Δn ≃ 2.5 and Δκ ≃ 2.75, respectively.     

电子激励表面等离极化激元的粒子模拟

采用极化电流微分方程,对贵金属中自由电子与外电场的共振过程进行描述。将该微分方程与麦克斯韦方程相结合,运用时域有限差分(FDTD)方法,在粒子PIC模拟软件CHIPIC3D的基础上,实现了电子激励表面等离极化激元(SPPs)的模拟。通过对100 keV电子平行于银薄膜表面运动、激励起表面等离极化激元的模拟,观测并分析了SPPs的场强及模式在银薄膜表面的分布,并验证了模拟结果的正确性。     

Direct excitation of the Tamm plasmon-polaritons on a dielectric Bragg reflector coated with a metal film

Tamm plasmon-polariton is a surface state or surface wave formed at the boundary between a metal and a dielectric Bragg reflector. In order to directly excite the Tamm plasmon-polaritons with unit transmission, we design a structure of Bragg reflector coated with a metal film. Through the Bloch theorem of periodic structures and transfer matrix method, we deduce the existence conditions of the Tamm plasmon-polaritons. For a a finite structure, the Tamm plasmon-polaritons can be excited, which is dependent on the thickness of metal, the period number of the Bragg reflector, the incident direction and frequency. On proper conditions, a perfect transmission for the Tamm plasmon-polariton mode can be achieved without the use of attenuated total reflection prism coupling or diffraction grating.     

Magnetic surface anisotropy of transition metal ultrathin films

In order to study the magnetic anisotropy of transition metal ultrathin films, we have performed tight-binding calculations including spin-orbit coupling. Beside the anisotropy energy these calculations also yield the orbital moment, which turns out to be much more anisotropic than in bulk materials. The effects of interfacial mismatch and roughness are discussed within phenomenological models. We also briefly review experimental results on the magnetic surface anisotropy (MSA) in transition metal ultrathin films. In some cases such as Au/Co/Au(111) sandwiches the MSA wins the competition with the shape anisotropy arising from the magnetostatic energy: below a critical thickness this leads to aperpendicular spontaneous magnetization. We show the effects of this crossover on the hysteresis loops and on the magnetoresistance, and the effects of interface roughness on the critical thickness.     

A new model analysis of the third harmonic voltage in inductive measurement for critical current density of superconducting films

The critical current density J c is one of the most important parameters of high temperature superconducting films in superconducting applications,such as superconducting filter and superconducting Josephson devices.This paper presents a new model to describe inhomogeneous current distribution throughout the thickness of superconducting films applying magnetic field by solving the differential equation derived from Maxwell equation and the second London equation.Using this model,it accurately calculates the inductive third-harmonic voltage when the film applying magnetic field with the inductive measurement for J c.The theoretic curve is consistent with the experimental results about measuring superconducting film,especially when the third-harmonic voltage just exceeds zero.The J c value of superconducting films determined by the inductive method is also compared with results measured by four-probe transport method.The agreements between inductive method and transport method are very good.     

Scattering of an electromagnetic wave from a slightly random cylindrical surface: horizontal polarization

Abstract

The scattering of an electromagnetic wave from a random cylindrical surface ir studied for a plane-wave incidence with S-(TE) polarization, by means ofthe stochastic scattering theory developed by Nakayama, Ogura. Sakati et al. The theory is based on the Wiener-Ito stochastic functional calculus combined with the group-theoretic consideration concerning the homogeneity of the random surface. The random surface is assumed to be a homogeneous Gaussian random field on the cylinder C, homogeneous with respect to the group of motiolrs on C: translations along the axis and rotations around the axis. An operator D operating on a random field on C is introduced in such a way that D keeps the homogeneous random surface invariant This gives a reprerentation of the cylbdrical group and commutes with the boundary condition and the Maxwell equation. Thus, for an injection of the mth cylindrical TE or TM wave, which is a vector eigenfunction of the D operator, the scattered random wave field is an eigenfunctiou with the same eigenvalue: it satisfies the Maxwell equation and is a stoch-tic Iunctional of the Gaussian random surface, BO that it can be expressed in a vector form of the Wiener-Ito expansion in t e m of TE and TM waves and orthogonal functional. of the Gaussian random measures associated with the random cylindrical surface. In the analysis the random surface is modelled by an approximate boundaiy condition representing a perfectly conducting cylindrical surface with a slight roughness. The boundary condition on the random cylinder is transformed into a hierarchy of equations for the Wiener kernels which can be solved approximately. The random wave field for a plane-wave injection is obtained by summing these fields over m. From the stochastic representation of the electromagnetic field so obtained, various statistical characteristics can be calculated the coherent scattering amplitude. total coherent power flow, incoherent power flow, differential sections for coherent rcatlerhig and incoherent scattering, etc. The power conservation law is cast into a stochastic electromagnetic version of the optical theorem stating that the total scatteiing cross section is given by the imaginary part of the forward coherent scattering amplitude. Numerical calculations are made for a planewave injection with S-(TE) polarization. The case of p-(TM) polarization can be treated in a similar manner.     

Regular models with quadratic equation of state

We provide new exact solutions to the Einstein–Maxwell system of equations which are physically reasonable. The spacetime is static and spherically symmetric with a charged matter distribution. We utilise an equation of state which is quadratic relating the radial pressure to the energy density. Earlier models, with linear and quadratic equations of state, are shown to be contained in our general class of solutions. The new solutions to the Einstein–Maxwell are found in terms of elementary functions. A physical analysis of the matter and electromagnetic variables indicates that the model is well behaved and regular. In particular there is no singularity in the proper charge density at the stellar centre unlike earlier anisotropic models in the presence of the electromagnetic field.