Vertex correction and conductivity in 2D Dirac-like systems with non-conserving spin disorder

We determine the classical diffusion of two dimensional Dirac-like quasiparticles, in the presence of conserving spin disorder (scattering off electric impurities) and non-conserving spin disorder (scattering off magnetic impurities). We use the Kubo formula for the conductivity tensor and employ diagrammatic perturbation theory to calculate the vertex correction and the renormalisation of the current operator for both electric and magnetic scattering. Scattering off electric impurities is isotropic and the current operator renormalised to two times the bare current operator irrespective of the direction of the dynamics, as usual for Dirac-like fermions. For magnetic scattering the renormalisation of the current operator depends on the direction of the dynamics and on the polarisation of the magnetic impurities, making the system anisotropic. We calculate the anisotropic magnetoresistance (AMR) and analyse it as a function of the ratio of the strength of the electric to the magnetic scattering potentials, for short range Gaussian correlation.     

霍尔推力器放电通道溅射腐蚀计算

 为了预示霍尔推力器的寿命,建立了推力器粒子束放电通道的2维电磁场模型,模拟的推进剂为氙。利用PIC方法跟踪粒子在电磁场中的运动。磁场的求解采用拉普拉斯方程,电场的求解采用泊松方程。电子由阴极喷入通道,并在电磁场中与原子发生电离碰撞生成离子。在跟踪离子的过程中记录下撞击到内外壁面的离子个数、角度和能量。利用记录下的参数进行腐蚀计算,得到当溅射阈值能量分别为10,20,30,40,50 eV时通道壁面的腐蚀速率。推力器放电通道出口附近的最大腐蚀速率约为1.7×10^-9 m/s。     

Electron Tunneling Through Metallic Particles and Quantum Dots Connected to Ferromagnetic Leads

Electronic transport through small metallic particles and quantum dots, coupled by tunneling barriers to ferromagnetic electrodes, is studied theoretically. Nonequilibrium Green function techniques are used to calculate electric current and tunnel magnetorersistance due to rotation of the magnetic moments of external electrodes.     

Gluon transport equations,plasma oscillations,and screening

The gluon transport equations (Phys. Lett. 177B (1986) 402) are reconsidered to derive a consistent semiclassical limit. Introducing the color current of gluon fluctuations around a classical mean field, we calculate the color permeability function of a collisionless gluon plasma in linear response approximation. The dispersion relations and electric screening length agree with one-loop high temperature QCD results. We find no magnetic screening atO(g ²) and predict transverse magnetic plasma oscillations similar to electric ones. The extension to include particle production by a mean color field is shortly described.     

感生电场与动生电场的等效性探究

本文认为在感生电场的情况下,磁场的强弱变化可以引起磁场自身的横向运动,使得线圈中电子相对于磁场发生运动,从而等效为一个动生电场,受到洛伦兹力的作用.借助磁感线模拟磁场的运动方式,得到圆形回路中任意一点与磁场相对运动速度的表达式,进而推得该＂等效动生电场＂中的洛伦兹力.以螺线管为例,验证该方法可以解释感生电场所满足的规律.将感生电场与动生电场的产生原因统一为导体中电子与磁场的相对运动,相应电动势的非静电力统一为洛伦兹力.     

Spin and electric field gradient texture studies by Mössbauer spectroscopy with polarized gamma rays

From Mössbauer spectra of⁵⁷Fe with elliptically polarized radiation we fit the coefficients of the spin (or electric field gradient) texture function expanded in real spherical harmonics up to 1=2. We determine, and show in perspective graphs, the spin texture of the surface of a transformer metal sheet (Fe?Si), of magnetic videotapes (demagnetized and magnetized) and the electric field gradient texture of a powder of an organometallic compound. We calculate some averages that have an important physical significance.     

Magneto-electric response functions for simple atomic systems

We consider a simple atomic two-body bound state system that is overall charge neutral and placed in a static electric and magnetic field, and calculate the magneto-electric response function as a function of frequency. This is done from first principles using a two-particle Hamiltonian for both an harmonic oscillator and Coulomb binding potential. In the high frequency limit, the response function falls off as 1/ω ² whilst at low frequencies it tends to a constant value.     

Localized donor states in axially symmetrical heterostructures

We present a general method for calculating the energy spectrum of donors confined in heterostructures with axial symmetry in the presence of magnetic and electric fields applied along the symmetry axis. The donor’s wave functions are chosen as a product of the Slater orbitals and an envelope function that is a solution of a one-dimensional differential equation, which we derive starting from Schrödinger’s variational principle. We calculate the energies of the ground and some excited states of a donor confined in multiple quantum wells and a nanowire superlattice as functions of the donor position, electric and magnetic fields for structures with different numbers and widths of the wells and the barriers. Our method could be applicable to a variety of complex quantum-confined semiconductor structures for which more rigorous approaches require extensive numerical calculations.     

截面异形的轴向变化磁场产生的感生电场

介绍一种计算感生电场的数值方法,它既可用于计算柱形分布均匀变化磁场所产生的感生电场,也可计算分布在任意界面上的变化磁场所产生的感生电场,并给出了一些计算实例．     

Green's function for arbitrarily shaped dielectric bodies of revolution

In this paper, a solution is developed to calculate the electric field at one point in space due to an electric dipole exciting an arbitrarily shaped dielectric body of revolution (BOR). Specifically, the electric field is determined from the solution of coupled surface integral equations (SIE) for the induced surface electric and magnetic currents on the dielectric body excited by an elementary electric current dipole source. Both the interior and exterior fields to the dielectric BOR may be accurately evaluated via this approach. For a highly lossy dielectric body, the numerical Green's function is also obtainable from an approximate integral equation (AIE) based on a surface boundary condition. If this equation is solved by the method of moments, significant numerical efficiency over SIE is realized. Numerical results obtained by both SIE and AIE approaches agree with the exact solution for the special case of a dielectric sphere. With this numerical Green's function, the complicated radiation and scattering problems in the presence of an arbitrarily shaped dielectric BOR are readily solvable by the method of moments.     

Exchange of helicity in a knotted electromagnetic field

There are solutions of Maxwell equations in vacuum in which the magnetic and the electric lines have a nontrivial topology. This behaviour has physical consequences since it is related to classical expressions indicating aspects of the photon content of the electromagnetic field. In this work we present for the first time an exact solution of Maxwell equations in vacuum, having non trivial topology, in which there is an exchange of helicity between the electric and magnetic part of such field. We calculate the temporal evolution of the magnetic and electric helicities, and explain the exchange of helicity making use of the Chern‐Simon form. We also have found and explained that, as time goes to infinity, both helicities reach the same value and the exchange between the magnetic and electric part of the field stops.     

由铁磁质限定的无限深槽内线电流的磁场

利用复数坐标系z上的施瓦茨-克利斯多菲变换和镜像法,计算由铁磁质限定的无限深槽内线电流的磁场,给出磁矢势的分布和磁感线方程,并利用数学工具软件MATLAB绘制出其磁感线分布图.     

经典洛伦兹磁力和广义洛伦兹磁力解释电子感应加速器的本质

介绍了虚构的法拉第定律与电子感应加速器不合理,用完整洛伦兹磁力解释电子感应加速器合理有效。     

Interactions of coherent electromagnetic radiation with nuclei

When coherent electromagnetic radiation resonantly couples two levels of a nucleus, the system can emit photons by stimulated and by spontaneous emission. The spontaneous emission spectrum is defined as the Fourier transform of the first-order correlation function of the magnetic or electric field operator. This function can be expressed in terms of one-time and two-time averages of nuclear operators. The one-time averages can be calculated by solving the Bloch-type equations for the matrix elements of the nuclear density operator. Application of the quantum regression theorem permits to calculate two-time averages with the aid of one-time averages and hence the radiated spectrum.     

The Influence of Neutral Particle Sources on the Dynamics of Tokamak Plasmas. II. Particle Dynamics and Induced Electromagnetic Fields

In part I of our paper [1] a kinetic theory of the influence of neutral particle sources on the dynamics of tokamak plasmas has been developed and the general solution of this problem has been given for an arbitrary source function. By the use of these results we calculate in this part II the particle's distribution function for different simple source functions. In the case of recycling perpendicular to the limiter surface we derive analytical expressions for the charge density, the induced electric potential and the anomaleous electron density flux transverse to the magnetic field.     

Random Motion of a Charged Test Particle with a Constant Classical Velocity in a Spacetime with a Plane Boundary

We study the random motion of a charged test particle coupled to electromagnetic vacuum fluctuations near a perfectly reflecting plane boundary with a nonzero classical constant velocity in a direction parallel to the plane. We calculate the mean squared fluctuations in the velocity and position of the test particle taking into account both fluctuating electric and magnetic forces. Our results show that the influence of fluctuating magnetic fields is, in general, of the higher order than that caused by fluctuating electric fields and is thus negligible.     

垂直电磁场中He原子的吸收谱和回归谱的理论计算

半经典闭合轨道理论已经成功地计算了在外加磁场和平行电磁场中的里德堡原子的回归谱.但对于垂直电磁场中的里德堡原子,理论和计算都变得更为复杂.本文把闭合轨道理论推广到三维情况,采用 B.Hüpper的模型势计算了ε=-0.03,主量子数n≈ 40,m=0下He原子在垂直电磁场中的光吸收谱和回归谱,并和H原子在垂直电磁场中的回归谱作比较,突出了实散射的贡献.计算中应用了离子实散射的分区自洽迭代方法,并考虑到轨道的多次重复和离子实的多次散射效应.这是对闭合轨道理论的验证和进一步推广.     

Negative refractive index in artificial metamaterials

We discuss optical constants in artificial metamaterials showing negative magnetic permeability and electric permittivity and suggest a simple formula for the refractive index of a general optical medium. Using the effective-field theory, we calculate the effective permeability and the refractive index of nanofabricated media composed of pairs of identical gold nanopillars with magnetic response in the visible spectrum.     

Shift in cyclotron resonance of electrons on liquid helium surfaces

We calculate the increase in cyclotron resonance frequency for electrons trapped within dimples on a liquid helium surface, when a vertical electric field is applied in addition to the strong vertical magnetic field.     

Effects of anomalous magnetic dipole and electric quadrupole moments of the charged weak boson on (g−2)μ

We calculate the effect on the muon anomaly of anomalous magnetic dipole and electric quadrupole moments of the charged weak boson and discuss the constraints on those quantities derived from the experimental data.