Vol. 37, No. 6 (1988)
1988, 37 (6): 881-891. doi: 10.7498/aps.37.881
The self-consistent mean field in the many-body correlation dynamics is discussed in detail. It is shown that the self-consistent mean field exists in general in many-body correlation dynamics for both stationary and non-stationary cases. The many-body correlations enter the mean field through the two-body correlation c2 and the corresponding collision term I. The role played by I is twofold i.e., dynamical effects and statistical effects on single particle states. The many-body correlations also manifest their effects on the many-body energy and yield an energy expression different from the conventional expression in the HF-Bruc-kner theory.
THEORETICAL CALCULATIONS OF THE QUANTUM DIFFERENTIAL SPECTRUM OF TRANSITION RADIATION FROM A STACK OF BERYLLIUM FOILS
1988, 37 (6): 892-898. doi: 10.7498/aps.37.892
In this paper, the formulas of quantum differential spectrum of the transition radiation, which are produced when a medium energy relativistic electron passes through a single foil or a stack of foils, are derived on the basis of the macroscopic pola rization theory of me-dium. Using these formulas, we calculate the spectra for a single beryllium foil and a stack of beryllium foils and obtain the results that agree with experiments.
1988, 37 (6): 899-905. doi: 10.7498/aps.37.899
In this paper, formulas of electromagnetic field diffraction on a metal filament are given. We report the experimental and calculated results of diffraction of linear polarized light on a metal slit and its complemencary diffracting screen of filament. The polarization effect in diameter measuremenr of filament by diffraction method is presented quantitatively. Calculated results agree with experimental results.
1988, 37 (6): 906-915. doi: 10.7498/aps.37.906
Photoluminescence technique are used to diagnose the quality of quantum wells. The influences on the fluorescence spectra of quantum wells due to thickness fluctuations of quantum wells, fluctuation of aluminium content, various defects, and unintentional impurities, are discussed. And inversely, the possible reasons causing degradation of quantum wells are deduced from the photoluminescence spectra. To some extent the diagnosis can provide certain basic information for improving the molecular beam epitaxy technology.
MEASUREMENT OF THE DENSITY OF GAP STATES IN AMORPHOUS SEMICONDUCTORS BY INFRARED STIMULATED CURRENTS
1988, 37 (6): 916-923. doi: 10.7498/aps.37.916
A new method of measuring the density of gap states in amorphous semiconductors by employing a two-beam photoconductivity experiment is reported. In the two-beam experiment, an intensive bandgap pump light is used to create non-equilibrium carriers and most of these carriers are trapped in the gap states. Then, at a latter time td after turning off the pump light, these trapped carriers are re-excited by an infrared probe light A photoconductivity overshoot, which depends on the delay time and temperature, is observed in the onset process of IR excited photoconductivity. The results are discussed using the multiple trapping theory. The distribution of the density of gap states is deduced from the experiment.
1988, 37 (6): 924-930. doi: 10.7498/aps.37.924
The growth of Ag ultramicro-particles in BaO semiconductor film are investigated bv tran missive electron microscope. The fine growth of Ag ultramicro-particles in BaO film are discovered in the samples after proper heat treatment. We also contrasted the structure difference of single-layer-made and multilayer-made Ag + BaO films. The growth properties of Ag ultramicro-particles in Ag + BaO films with different Ag content are also studied. The Ag ultramicro-particles do not form maze structure in Ag + BaO film with high Ag content, but form isolated Ag particles. There are BaO layer of a few nm thick between every two Ag particles.
1988, 37 (6): 931-940. doi: 10.7498/aps.37.931
We discuss the effect of surface roughness on the surface polariton modes on semi-infinite superlattices. We have derived the Green's function for the Maxwell equations in the case of a semi-infinite superlattice with a smooth surface. The dispersion relations for surface polaritons in the case of a rough surface, are then obtained; The main conclusion is that in this case a new mode, the surface localized TE surface polariton, appears, as can be tested experimentally.
In this paper, the crossover effect of the dimensionality in the disordered layer system is studied by using the post-CPA method for the vertex. The effective dimensionality of the system is determined by the interlayer coupling t. It is shown that Anderson transition will occur at the critical value tc. Boltzmann conductivity, the dynamical conductivity corresponding to the maximum crossed diagrams, the d. c. conductivity and the localization length near the critical point are calculated.
1988, 37 (6): 950-958. doi: 10.7498/aps.37.950
In the present work, the behaviors of a-Ge/Ag composite layers are studied. These layers are composed of amorphous Ge film with thickness 2000 ? and Ag film with different thickness. It is found that, when the thickness of Ag film decreases, the electrical resistivity of the composite layer at room temperature becomes more and more smaller than that of Ag mono-layer with the same thickness. The proximity effect at room temperature is shown clearly by experiment. As the samples are annealed, we obtain various R(Ta)-T relations under different annealling temperature Ta and various dependences of R300k on Ta for layers withe different thickness of Ag film. Based on structural analysis by XRD and composition analysis by EMP, and observation with TEM and SEM, the new phenomena are explained.
1988, 37 (6): 959-966. doi: 10.7498/aps.37.959
The maximal and complete analytic extension of a globally regular Schwarzschild black hole is given in the Kruskal coordinate. The junction conditions on null hypersurface are discussed. The asymptotic space-time stuctures of singular and nonsingular Schwarzschild black holes are compared. It is shown that a nonsingular stable black hole can exist.
A POSSIBLE HEAVY-FERMION MECHANISM OF SUPERCONDUCTIVITY——ELECTRON-SLAVE BOSON SUPERCONDUCTING MECHANISM
1988, 37 (6): 967-973. doi: 10.7498/aps.37.967
Using the Anderson lattice, the heavy-fermion superconductivity is discussed. In the long wavelength limit of Slave boson field, the mutual interaction between the same type quasipar-ticles is attractive by one-Slave boson exchange and the heavy-fermion superconductivity is induced by the first type quasiparticles-quasi-f electrons only.
1988, 37 (6): 974-977. doi: 10.7498/aps.37.974
We reported here the effect of transition metals TM (TM = Nb, V, Cr, Mn, Co, Ni and Cu) on magnetic moment. Curie temperature and crystallization temperature of amorphous Nd15Fe79B6 alloys. The average internal fields for these alloys were obtained by M?ssbauer spectroscopy.
1988, 37 (6): 978-982. doi: 10.7498/aps.37.978
The metallic glasses AgxCu50-xZr50 are prepared by an induction furnace followed by melt spinning in vacuum. It is found that amorphous alloys can be obtained in the range xc of the metallic glasses AgxCu50-xZr50 with x = 2, 4, 6 and 10 are obtained. The activation energys En of crystallization are determined by the Kissinger method. It is shown that the bigger is the x in metallic glasses AgxCu50-xZr50, the less stable is the glasses. A comparison of the study on the crystallization of the glasses in argon with that in the air suggests that the second exothermal peaks are oxidation peaks.
Stark structure of Sr atom Rydberg states in the vicinity of n = 12 and n = 13 were me-asured by multistep excitation method with ππ polarized lasers. The Stark map exhibited the linear behaviour of Stark manifold of Sr atom in low electric field. The crossing and antic-rossing structure of levels, which depends on the quantum effects, were discussed.
1988, 37 (6): 989-995. doi: 10.7498/aps.37.989
After analyzing different experiments of population inversion in the X-ray region, we proposed a new method of a micro-tube heated by a laser beam, and observed the high population inversion between ls3p and 1s4p levels and ls3p and ls5p levels. The physical mechanism was discussed in some detail.
1988, 37 (6): 996-1002. doi: 10.7498/aps.37.996
Some modifications are made on the Molnar theory. And the analytical method for finding the transient wave-form in Townsend discharge with various kinds of metastables is given.
1988, 37 (6): 1003-1009. doi: 10.7498/aps.37.1003
The crystal theory is formulated for treating the vibrational Green's functions of alloys. The configurations of the alloy could be symmetrized in virtue of the theory of permutation groups. The Hamiltonian of the alloy could be block diagonalized using the franslation group of the lattice, and completely diagonalized by applying Wilson's GF matrix method. So the inverse matrix of Green's functions is solved. Phonon's Hamiltonian and Green's func-tions are also mentioned.
1988, 37 (6): 1010-1013. doi: 10.7498/aps.37.1010
The fractional quantum Hall effect system is analysed in the mass centre coordinate. An equation which restricts the combination of the single electron angular momentum is obtained. By using this restrictive relation, the dimension of the Hamiltonian eigenequations could be reduced. We also calculated the eigenenergies in the mass centre coordinate with the effect of the neutralizing background charges included.
1988, 37 (6): 1014-1017. doi: 10.7498/aps.37.1014
An exact real space renormalisation group is applied to study the adsorption of a single self-avoiding walk on fractal spaces. Exact results of critical exponent ν and crossover exponent φ show that de Gennes' conjecture φ =1-ν is invalid. The phase diagram has qualitatively the same shape as it has on Euclidean space, except for a unique and important difference that the adsorption transition would take place for a single polymer chain at a hard wail exerting a infinitesimal short-range attractive force on the fractal space instead of a finite one as on Euclidean space.
1988, 37 (6): 1018-1024. doi: 10.7498/aps.37.1018
The comb-pulse response of a system of half-integer quadruplar nuclei depends on the quadrupolar coupling constant ωq. When the average rf field strength ωe (in rad. s-1) satisfies the condition ωq/ωee/(2π); and when ωq/ωe > 2.0, the resul tant line appears at 2ωe/(2π). Theoretical calculations are in agreement with experiments.These consequences indicate that the comb-pulse sequence will probably become a powerful technique for investigating phase transitions and dynamic processes in these systems.
1988, 37 (6): 1025-1029. doi: 10.7498/aps.37.1025
The C-V characteristic of a silicon p-n diode grown by molecular beam epitaxy (MBE) technique was carefully studied in the case that the space charge region reached the edge of MBE layer. Based on the theoretical analysis and experimental measurement, the impurity concentration in unintentionally doped n-type MBE layer was determined to be 8.0×1014cm-3. This method is shown to be a new way to find out impurity concentrations in supper-thin semiconductor layers.
1988, 37 (6): 1030-1035. doi: 10.7498/aps.37.1030
The effect of diagonal disorder on the upper critical field of the local electron pair system is studied in the framework of the mean field approximation. It is obtained that this kind of disorder greatly changes the temperature behavior of H(c2). Comparing che upper critical field of this system with those of heavy fermion superconductors CeCu2Si2 and UPt3, we find that it could have the similar unusual temperature dependence.
1988, 37 (6): 1036-1041. doi: 10.7498/aps.37.1036
When the temperature is far below Tc, a set of electric voltage steps appear on the H-V or I-V curves of the metallic glass Zn78Co22 under longitudinal magnetic fields. The oc-curing conditions and the structural characteristic of steps have been compared systematically with the steps existing in homogeneous superconductors of quasi-one or quasi-two dimension systems. A model of superconducting phase separation and the idea of phase slip centers have been used to explain the observed phenomena.
1988, 37 (6): 1042-1047. doi: 10.7498/aps.37.1042
The relation between superconductivity and phase structure of YBa2-xSrxCu3O7-δ system has been studied systematically. It is found that when 0c increases monotonously. The mechanism of the effect of Sr atom on Tc and superconductivity have also been discussed.
1988, 37 (6): 1048-1052. doi: 10.7498/aps.37.1048
We have studied the relation between the low-temperature resistance of single phase Ba2YCu3O7-δ and magnetic field, temperature and measuring current. The results show that the resistance behavior varies obviously with the strength and direction of the field as well as the measuring current. We suggest that all the results are associated with the granular structure of the sample.