The bipolaron theory of high-temperature superconductors

An outline is given for the bipolaron theory of high-temperature superconductivity, both for the cubic bismuth oxide and the copper oxide materials. It is emphasized that the BCS theory takes this form for strong interaction. The possible role of spin polarons in the latter is also discussed.     

On the formation and stability of the Fröhlich bipolaron in two- and three-dimensional systems

Summary Within the framework of Rayleigh-Schr?dinger perturbation theory the bound state of two electrons in polar crystals is investigated in various dimensional systems. It is found that Fr?hlich bipolaron can exist in both two and three dimensions in the strong-coupling region, the binding being stronger in the lower dimension. The stability criterion for the formation of the Fr?hlich bipolaron is estimated to yield better results compared to the values quoted in the literature. The author of this paper has agreed to not receive the proofs for correction     

Large-N reduction in the continuum three-dimensional Yang-Mills theory

Numerical and theoretical evidence leads us to propose the following: Three-dimensional Euclidean Yang-Mills theory in the planar limit undergoes a phase transition on a torus of side l=l(c). For l>l(c) the planar limit is l independent, as expected of a noninteracting string theory. We expect the situation in four dimensions to be similar.     

Localization transition of the three-dimensional lorentz model and continuum percolation

The localization transition and the critical properties of the Lorentz model in three dimensions are investigated by computer simulations. We give a coherent and quantitative explanation of the dynamics in terms of continuum percolation theory and obtain an excellent matching of the critical density and exponents. Within a dynamic scaling ansatz incorporating two divergent length scales we achieve data collapse for the mean-square displacements and identify the leading corrections to scaling. We provide evidence for a divergent non-Gaussian parameter close to the transition.     

过苯胺黑聚合物的双极化子态

利用改进的Ginder-Epstein模型研究聚苯胺黑的双极化子态, 给出其键序波幅、芳环扭角、电子能级、理论吸收谱和电荷分布,并与极化子进行对比。结果发现双极化子激发能为3.08eV, 晶格驰豫宽度涉及12格点与极化子相当;键交错驰豫深度大约为极化子的2倍,畸变中心芳环扭角高达68.35°大于极化子中心扭角的2倍。两个能隙态几乎简并,吸收谱低能峰为1.6eV。     

过苯胺黑聚合物的双极化子态

利用改进的Ginder-Epstein模型研究聚苯胺黑的双极化子态,给出其键序波幅、芳环扭角、电子能级、理论吸收谱和电荷分布,并与极化子进行对比.结果发现双极化子激发能为3.08 eV,晶格驰豫宽度涉及12格点与极化子相当;键交错驰豫深度大约为极化子的2倍,畸变中心芳环扭角高达68.35°大于极化子中心扭角的2倍.两个能隙态几乎简并,吸收谱低能峰为1.6 eV.     

Spatial configuration of the bipolaron and the virial theorem

The conditions of the virial theorem imposed on the dependence of the total energy of a system consisting of two polarons on the distance between the centers of the polarization wells are analyzed for various trial two-electron functions in the limit of strong electron-phonon coupling. It is shown that the inclusion of the direct dependence of the wave function of the system on the interelectron distance (correlation effects) does not break the conditions of the virial theorem. This theorem holds for a single-center and a two-center configuration corresponding to a subsidiary minimum, which disappears when the electron correlations are included.     

Computer simulation study of bipolaron formation

Monte Carlo computer simulation techniques are used to study the formation of bipolarons on a lattice. The transition between the three possible states, extended, twopolaron, and bipolaron is studied. The phase diagram as a function of the strengths of the electron-phonon coupling and repulsive interaction is determined.     

The impedance function of a confined polaron and bipolaron: The single-path-integral approach

We use the single-path-integral to calculate the impedance function of the polaron and bipolaron in quantum confinement with the presence of the external fields. The expectation values of the classical equation of motion is considered in order to obtain the impedance function. The mobility of the polaron and bipolaron in quantum confinement is also calculated in the direction parallel and perpendicular to the magnetic field. Without trapping, we also calculate the effective mass of the bipolaron in the magnetic field.     

An experiment on the existence region of dominance in pitch perception

An experiment with a certain random signal reveals that the dominant region for pitch perception is somewhat larger than previously reported.     

Investigation of the water-vapor continuum in the THz region using a multipass cell

Laboratory absorption measurements of the water-vapor continuum in the far infrared region from 12 to (0.4 - 1.83 THz) were obtained using a multipass absorption cell, a Fourier transform spectrometer and a liquid-He-cooled bolometer detector. Measurements were made at a temperature, with water vapor and nitrogen pressures up to 2.2 and , respectively. The effects of the choice of lineshape function and far-wing cut-off factors on the reported continuum absorption are analyzed by modeling the resonant water-vapor spectrum using van Vleck-Weisskopf and Lorentzian lineshapes. Comparisons with available microwave data and model calculations are also presented.     

Dichotic pitches as illusions of binaural unmasking. III. The existence region of the Fourcin pitch

Two experiments explored the existence region of the Fourcin pitch. In each experiment, detectability was assessed by measuring listeners' ability to discriminate pitch changes. In the first experiment, the detectability of the pitch was measured as a function of the number of noises used to generate it. In the second experiment, the pitch was generated using two noises with equal and opposite interaural delays and detectability was measured as a function of the difference between these two delays, and thus of the perceived pitch height. In each case, the experimental results were compared with the predictions produced by a model of binaural unmasking, based on equalization cancellation, that had been designed to recover broadband sounds, such as speech, from interfering noise [Culling and Summerfield, J. Acoust. Soc. Am. 98, 785-797 (1995)]. The model accurately predicted the results from experiment 1, but failed to show an adequate decline in performance for small differences in interaural delay (corresponding to higher perceived pitches) in experiment 2. A revised model, based on similar principles, but using data on listeners' sensitivity to interaural decorrelation, rather than an equalization-cancellation mechanism, was able to predict the results of both experiments successfully.     

Modulated K structures in the supercritical region of existence of peeling solid solutions

The conditions under which solid solutions can exist in the spinodal region have been considered. It is shown that, in the absence of effective kinetic mechanisms implementing decomposition processes, modulated K structures can be formed in a solid solution, which are a particularly ordered impurity distributions in a high-temperature phase.     

Theory of the existence of a two-phase region in ternary ordered fcc alloys

The limiting temperatures of the two-phase region in ternary ordered fcc alloys of the quasibinary B₃A-B₃D system are found on the basis of equality of the chemical potentials of the components of the ordered and disordered phases (in the Gorskii-Bragg-William approximation). The effect of the relative magnitudes of the three ordering energies on the nature of the phase diagrams of the ternary ordered alloy is analyzed.Translated from Izvestiya VUZ. Fizika, No. 7, pp. 54–60, July, 1970.     

Electron correlations and instability of a two-center bipolaron

The energy of a large bipolaron is calculated for various spacings between the centers of the polarization potential wells of the two polarons with allowance made for electron correlations (i.e., the explicit dependence of the wave function of the system on the distance between the electrons) and for permutation symmetry of the two-electron wave function. The lowest singlet and triplet 2³S states of the bipolaron are considered. The singlet polaron is shown to be stable over the range of ionic-bond parameter values η≤η_m≈0.143 (η=?_∞/?₀, where ?_∞ and ?₀ are the high-frequency and static dielectric constants, respectively). There is a single energy minimum, corresponding to the single-center bipolaron configuration (similar to a helium atom). The binding energy of the bipolaron for η → 0 is J_bp=?0.136512e⁴m^*/?²? _∞ ² (e and m* are the charge and effective mass of a band electron), or 25.8% of the double polaron energy. The triplet bipolaron state (similar to an orthohelium atom) is energetically unfavorable in the system at hand. The single-center configuration of the triplet bipolaron corresponds to a sharp maximum in the distance dependence of the total energy J_bp(R); therefore, a transition of the bipolaron to the orthostate (e.g., due to exchange scattering) will lead to decay of the bound two-particle state. The exchange interaction between polarons is antiferromagnetic (AFM) in character. If the conditions for the Wigner crystallization of a polaron gas are met, the AFM exchange interaction between polarons can lead to AFM ordering in the system of polarons.