Influence of magnetic impurities on the de Haas-van Alphen oscillations

Using a simple extension of Shiba's formula for the de Haas-van Alphen-oscillations, the influence of scattering by magnetic impurities is studied. Already for a classical spin model one obtains a minimum in the dHvA amplitudes as function of the magnetic-field, which is influenced by normal scattering. The change of this behavior for the Anderson model is studied within the Non-Crossing-Approximation, and raises questions for a comparison between experiment and theory.     

Polarization phenomena in the intermediate energy elastic deuteron scattering from <Superscript>16</Superscript>C and <Superscript>16</Superscript>O nuclei

A model based on the multiple diffraction scattering theory and the α-cluster model with dispersion of target nuclei is proposed for describing the behavior of observables for the elastic deuteron scattering from ¹²C and ¹⁶O nuclei at intermediate energies. Differential cross-sections and analyzing powers calculated within this approach for incident-deuteron energies of 400 and 700 MeV are in a reasonable agreement with experimental data.     

微波混沌腔体中的散射特性研究

以计算机机箱为研究目标,开展了电磁波耦合入计算机机箱腔体的散射问题研究.通过对其散射矩阵元的讨论和分析发现:可以通过辐射散射测量得到系统散射矩阵的系综平均;随着腔体损耗的增加,腔体散射系数的波动性减小;随着腔体损耗的进一步增加,插入相移分布逐渐趋于均一分布.通过Dyson圆系综讨论了归一化散射矩阵,计算机机箱腔体中存在波混沌散射.根据随机矩阵理论,微波混沌腔体的归一化阻抗矩阵具有统计通用性,且只与系统的损耗有关.     

Effect of local molecular ordering on the temperature behavior of the relaxation time of order-parameter fluctuations in the isotropic phase of PAA nematic liquid crystal

The behavior of the relaxation time of order-parameter fluctuations in the isotropic phase of PAA nematic liquid crystal was investigated on the basis of the spectra of depolarized (inelastic) light scattering in a wide temperature range including the immediate vicinity to the temperature of the nematic phase transition. The experimental data were analyzed within the Landau—de Gennes theory. The temperature limits of applicability of the Landau—de Gennes theory to the isotropic-phase dynamic properties are obtained. The minimum correlation length is determined, at which the effect of local ordering on the dynamics of slow orientational motion of isotropic-phase molecules is dominant.     

玻璃陶瓷PWG中的喇曼耦合系数对Raman散射的影响

应用修正的无序诱导散理论模型讨论了玻璃陶瓷（PbF2 WO3 GeO(PWG)中的喇曼耦合系数对Raman散射过程的影响。虽然普遍认为喇曼耦合系数是随频率而变化,但实际上它是空间相关函数的Furier分量,因此,严格地讲喇曼耦合系数是随动量（波矢q)而变化的,因而,玻璃陶瓷中的喇曼耦合系数描述了在Raman散射过程中发生在玻璃陶瓷中的动量交换相互作用。对于PWG中热活性拓动态的光谱分布曲线分析说明：指数衰减关系的卷积定性地表示了这个耦合系数。证明了简谐势与耦合系数有关的空间相关函数之和给出了非常类似于双阱势的畸变谐函数,根据弛豫模行为讨论了结合势的相关性。     

金属类散射体的Mie散射特性研究

基于Mie散射理论研究发现,各种金属在中红外区的的散射行为极为相似,是一种反照率极高但散射效率极低的散射体,数值研究揭示了这类散射体系的光学截面以及散射强度的分布的内在联系.     

Conductance of tubular nanowires with disorder

We calculate the conductance of tubular-shaped nanowires having many potential scatterers at random positions. Our approach is based on the scattering matrix formalism and our results analyzed within the scaling theory of disordered conductors. When increasing the energy the conductance for a big enough number of impurities in the tube manifests a systematic evolution from the localized to the metallic regimes. Nevertheless, a conspicuous drop in conductance is predicted whenever a new transverse channel is open. Comparison with the semiclassical calculation leading to purely ohmic behavior is made.     

Conductance fluctuations and quantum chaotic scattering in semiconductor microstructures

We review recent experiments on aperiodic conductance fluctuations in ballistic GaAs/AlGaAs microstructures in the shape of a stadium billiard and a circle with point-contact leads, measured at millikelvin temperatures. Much of the observed behavior can be analyzed within a semiclassical approach to quantum chaotic scattering. After a brief review of the Landauer-Buttiker formulation of coherent transport, a variety of novel experimental phenomena and comparisons to semiclassical theory are presented. In particular, we discuss quantum-enhanced backscattering, the power spectrum of conductance fluctuations, crossover to the high-magnetic-field and tunneling regimes, and an application allowing the rate of phase-randomizing scattering to be measured in chaotic ballistic microstructures.     

Polarization of out-of-plane scattering from microrough silicon

The polarization of light scattered by silicon with a small degree of microroughness was measured out of the plane of incidence. First-order vector perturbation theory for scattering from a rough surface predicts the behavior well. The data and the theory show Brewster-like angles where p?p scattering from surface microroughness vanishes, as well as a deterministic polarization in other directions.     

Dielektrische Theorie der unelastischen Streuung von Elektronen in Kristallgitterreflexe

Inelastic energy losses of free electrons (20–100 keV) scattered into crystal reflections are theoretically investigated. By extending the usual dielectric theory of solids to crystals these scattering processes can be explained as an immediate scattering into the reflections. The probability of scattering for an electron with a fixed energy loss is derived. This result agrees in the case of a homogeneous medium with the probability of scattering already known within the frame of the usual dielectric theory.     

Diffuse LEED intensities of disordered crystal surfaces: II. Multiple scattering on disordered overlayers

The diffraction of low energy electrons from disordered overlayers adsorbed on ordered substrates is treated theoretically by an extension of Beeby's multiple scattering method. A lattice gas model is assumed for the disordered adsorbate layer. Multiple scattering within a certain area around each atom — each atom of the overlayer and within the ordered substrate — is treated self-consistently, the remaining contributions to the total scattering amplitude being averaged. The theory can be used in the limiting cases of random distribution and of long range order within the adsorbate layer.     

Impact picture of pp,p̄p, π±p,and K±p elastic scattering from 20 to 5000 GeV

We give a simple model of hadron scattering from 20 to 5000 GeV which is based on the impact picture derived from quantum field theory. Numerical results, consistent with existing data are given and in addition we predict the general behavior of high energy hadron-hadron elastic scattering.     

Cooperative effects in Raman scattering

We formulate a theory of Raman scatterings from molecules based on the idea that the molecules within a small portion of the wavelength of the incident light should be considered as a single quantum-mechanical system. In such a system, if the final level involved in the Raman scattering is populated by the stimulated absorption or earlier scattering, the theory predicts that the scattering cross section would be increased approximately by a factor of the number of molecules existing in this final scattering level.     

光通过纳米颗粒随机散射体透射光强的计算及分析

光通过随机散射体后透射光强的估算,对于提取散射体内部无法直接测量或者无法直接观察的信息至关重要。在分析平行光束通过纳米圆形颗粒随机散射体出射面上光强组成的基础上推导了透射光强的计算公式,并指出多重散射理论、一阶多重散射理论和朗伯-比尔定律在一定近似程度上可以相对精确地估算透射光强。这三种方法的估算结果之间会出现四种相对关系。根据这些相对关系,分析了光在散射体内部传输时散射过程的特征以及各种散射过程对出射面光强的贡献大小。     

Breakdown of wave diffusion in 2D due to loops

The validity of the diffusion approximation for the intensity of multiply scattered waves is tested with numerical simulations in a strongly scattering 2D medium of finite extent. We show that the diffusion equation underestimates the intensity and attribute this to both the neglect of recurrent scattering paths and interference within diffusion theory. We present a theory to quantify this discrepancy based on counting all possible scattering paths between point scatterers. Interference phenomena, due to loop paths, are incorporated in a way similar to coherent backscattering.     

Pseudogaps in an incoherent metal

How are the properties of a metal changed by strong inelastic scattering? We investigate this question within the two-dimensional t-J model using extended dynamical mean field theory and a generalized noncrossing approximation. Short-ranged antiferromagnetic fluctuations lead to a strongly incoherent single particle dynamics, large entropy, and resistance. Close to the Mott transition at low hole doping a pseudogap opens, accompanied by a drop in resistivity and an increase in the Hall constant for both lower temperatures T and doping levels. The behavior obtained bears surprising similarity to properties of the cuprates.     

共振价键模型中正常态电阻率的讨论

本文运用线性响应理论推导共振价键(RVB)模型中holon-spinon散射和holon-phonon散射导致的正常态电阻率公式。计算结果表明:holon-spinon散射电阻率若用ρ-T^α公式拟合,α在1.4—1.5之间随温度变化;而声子散射电阻率在很大温度范围呈现线性温度行为。 关键词：