声子之间相互作用对半导体量子点中磁极化子性质的影响

研究了半导体量子点中磁极化子的性质.采用线性组合算符和微扰法,导出了半导体量子点中磁极化子的基态能量.在计及电子在反冲效应中发射和吸收不同波矢的声子之间相互作用时,讨论了对半导体量子点中磁极化子的基态能量的影响.通过数值计算表明,半导体量子点中磁极化子的基态能量随量子点的有效受限长度的减小而迅速增大,随磁场的增加而增加,对于弱磁场声子之间相互作用的影响不能忽略.     

Phonon excitation of quasiparticles in niobium and tantalum superconducting tunnel junction photon detectors

We report phonon pulse measurements of quasiparticle (qp) self-recombination and trapping by Abrikosov vortices in Nb and Ta superconducting tunnel junctions. The quasiparticle loss times, determined from the shape of the tunnel junction output pulse, were found to be strongly correlated with flux trapping. The measured results were compared with the model of Golubov and Houwman. It was found that qp self-recombination, as measured from the dependence of responsivity on absorbed phonon energy, was also modified by the presence of traps. A process of phonon-mediated de-trapping is proposed to explain the observed effects.     

Surface optical phonon-assisted electron Raman scattering in a free-standing quantum wire with ring geometry

We present a theoretical calculation of the differential cross section for the electron Raman scattering process associated with surface optical phonon modes in semiconductor quantum wires (QWs) with ring geometry. Electron states are considered to be confined within the QWs. We consider the Fröhlich electron-phonon interaction in the framework of the dielectric continuum approach. Some singularities for the ring with various sizes in the Raman spectra are found and interpreted. A discussion of the phonon behavior for the QWs with large and small sizes is presented. The numerical results are also compared with those of experiments.     

Solid State Physics View of Liquid State Chemistry III. Electrical Conductance of Pure and Impure Water

The ＇abnormally＇ high electrical conductivity ofpure water was recently studied by us using our protonic bond, trap and energy band model, with five host particles： the positive and negative protons, and the amphoteric protonic trap in three charge states, positive, neutral and negative. Our second report described the electrical charge storage capacitance of pure and impure water. This third report presents the theory of particle density and electrical conductance of pure and impure water, including the impuritons, which consist of an impurity ion bonded to a proton, proton-hole or proton trap and which significantly affect impure waters＇ properties.     

Structure and vibrations of cerium in silica glass from molecular dynamics simulations

Molecular dynamics simulations are performed to investigate the effect of cerium on the structural and vibrational properties of silica glass. At low-concentration levels, the cerium ions tend to generate longer bonds with bridging oxygens than nonbridging ones, the proportion of which is associated with the average bond length varied with cerium coordination. Formed in the presence of cerium, the bond angles exhibit strong dependence on the types of Ce-O bonds that bring about different angular distributions. Despite the discrepancy in the structures between Ce³⁺ and Ce⁴⁺, similar characteristics of vibrations are observed for the two states. In comparison with the glass formers, the vibrations of cerium that contribute primarily to the low-frequency region show a less localized behavior, whereas the acoustic-like and optic-like modes separate at a much smaller frequency.     

温度对非对称量子点中强磁耦合极化子声子平均数的影响

采用Huybrechts线性组合算符法和LLP变分法,研究了温度对非对称抛物量子点中强耦合磁极化子声子平均数的影响。数值结果表明,非对称量子点中强耦合磁极化子的声子平均数随温度的升高而减小。另外,温度还对磁极化子的声子平均数随量子点的横向受限强度、纵向受限强度、外磁场的回旋频率和电子-声子耦合强度的变化产生显著影响.     

Structural Relaxation Dynamics of ortho-Terphenyl

This paper analyzes molecular dynamicssimulation results on the small-molecule glass formerortho-terphenyl (OTP). The data can be describedwell using the coupling model of relaxation. Thedynamic susceptibility calculated from thedensity-density time correlation function is shown toapproximately conform to the scaling laws of modecoupling theory. Since the dynamic singularities ofmode coupling theory are absent in the coupling model,both approaches to high frequency structuralrelaxation can not be correct; the conformance to modecoupling theory indicates the non-uniqueness of modecoupling theory interpretation of data from fragileliquids. The non-cooperative relaxation time fordensity fluctuations in OTP is found to have the sameactivation energy as the shear viscosity in the hightemperature limit. This illustrates the relationshipbetween microscopic dynamic variables and the shorttime behavior of macroscopic properties, when theformer are analyzed according to the coupling model.     

Thermally Self-Consistent Monte Carlo Device Simulations

We present details of a Monte Carlo simulation code which is coupled to a Heat Diffusion Equation (HDE) solver. Through an iterative procedure, which bypasses the differences in electronic and thermal timescales, this coupled code is capable of producing steady-state thermally self-consistent device characteristics. Electronically-generated thermal flux is calculated by monitoring the net rate of phonon emission, which may be resolved both spatially and by phonon type. The thermal solution is extracted through use of a novel analytical thermal resistance matrix technique which avoids calculation of temperatures beyond the electronically important device region while including the large-scale boundary conditions. On application to a GaAs MESFET the expected thermal droop behaviour is obtained in the I-V characteristics and we find a linear relationship between peak lattice temperature and applied source-drain bias. At moderate biases the contribution of intervalley phonons to the thermal power output surpasses that of optical phonons.     

Phonons in Wurtzites, Fullerenes, and Nanotubes

The applicability of the dielectric and elastic continuum models for describing phonons in nanostructures is discussed. As an example, properties of confined, interface and propagating modes in wurtzite quantum-confined structures are described theoretically in terms of the dielectric continuum model and Loudon's model for uniaxial semiconductors. As a second example, dimensionally-confined acoustic phonon modes of fullerenes and carbon nanotubes will be described in terms of the elastic continuum model.