The existence and evolution of spherical membrane configurations in spherical-symmetric and self-similar spacetimes are studied, and a solution for the dynamics of membranes is obtained. A new interpretation for the origin and evolution of the cosmic matter-structures is acquired. It agrees well with the survey of astronomy.
Ferromagnetic resonance (FMR) has been used to investigate the magnetism of Fe overlayer on S-passivated GaAs(100) pretreated by CH3CSNH2. Comparing with the magnetism of Fe overlayer on clean GaAs(100), we find that sulfur passivation can prevent As diffusion into Fe overlayer and weaken the interaction of As and Fe. It results in enhancing the magnetism of Fe overlayer on GaAs(100). We also investigate the effects of the pre-annealing of S- passivated GaAs(100) substrate on the magnetism of Fe overlayers. The results show that the maximum effective magnetization can be obtained at annealing temperature of 400 degrees C. According to the experimental results of synchrotron radiation photoemission, it can be explained by the change of chemical composition and surface structure of the passivation layer on GaAs(100) surface after the annealing.
Microwave responses of YBa2Cu3O7-delta (YBCO) granular film have been studied at the microwave frequency of 30.5 GHz. In the absence of a magnetic field the dependence of a normal microwave response on the bias current is observed at a temperature close to T-c. When a magnetic field ranged from 5.0 mT to 33.0 mT is applied, the responses broaden and shift toward a lower temperature. In the superconducting state, the responses were found to be highly dependent on the magnetic field. For the current equal to 5.0 mA and a magnetic field above 17.0 mT the response increases and did not vanish even at a very low temperature, the fact is believed to be correlated to the anisotropic character of the structure.
The domain structures of Pt1-xCux/Co multilayer films in as-grown and remanent states have been investigated by using magnetic force microscope. The magnetic domain patterns are strongly influenced by the Cu concentration. For pure Pt/Co multilayer in as-grown state, its domain pattern is depicted as island-like one; however, with the Cu doped in Pt spacer layers, the doman patterns become dot-like, but the island-like domain pattern appears again for the Cu concentration of 14at%. The domain patterns variation can be attributed to the change of effective perpendicular anisotropy Kueff due to the effect of Cu atom doped in the Pt spacer layers. Besides, the domain structures of Pt/Co multilayer films in remanent state after the application of various perpendicular magnetic fields have also been studied.
Nanocrystalline V2O5 thin films were reactively radio-frequency magnetron-sputtered under optimal deposition parameters. Their electrochemical and electrochromic characteristics were investigated by cyclic voltammetry and in-situ monochromatic transmittance measurements. Upon lithium intercalation, V2O5 thin films showed a double electrochromic behavior depending on the wavelength and the intercalation extent. X-ray photoelectron spectroscopy results showed that part of the V5+ in V2O5 was reduced to V4+ during the Li+ intercalation process.
Population trapping via quantum interference in a multi-level system driven by a coherent field is investigated. The influences of the alignment of the transition dipole moments and the energy-level separation of the upper levels are taken into account. Detailed trapping population profiles under the different conditions are given. The research result is helpful for simplifying the theoretical model and selecting rational energy level system.
The temperature dependences of the layer parameters σn,z= , mn,z= and qn,z= of a magnetic Ising superlattice consisting of two ferromagnetic Ising materials with spins μ=1/2 and S=1 respectively, on a simple cubic structure, are examined using the effective field theory based on the use of a probability distribution technique that correctly accounts for the single site kinematic relations. According to the values of the exchange interactions, different qualitative types of phase diagrams are expected.
The electronic structures and geometry of a solid assembled out of cubic close packing of Al12Si clusters have been studied with an ab initio pseudopotential method and within the local density functional theory. Both the lattice constant of the solid formed and the atomic geometry of the clusters in it have been optimized through the ab initio method without adjustable variables. Our results show that the crystal composed of Al12Si clusters is a metal rather than a semiconductor. Interactions between Al12Si clusters in the solid are strong and the clusters are no longer inert under crystal field.
Hole-overdoped Bi2Sr2-xLaxCuO6+δ single crystals with two coexistent superconducting transitions have been intensively studied by measuring the dc magnetic susceptibility. It is found that the coexistence of these two phases cannot be attributed to any chemical or vortex dynamical effect but to some intrinsic driving force, such as the electronic-driven phase separation. Furthermore, the upper critical fields of the two phases behave in a rather different way; that is, one of them shows a "normal Hc2 behavior" which can be described by the critical fluctuation theory, while the other exhibits an "anomalous Hc2 behavior" and can be well explained by a recent theory based on an assumption of a Josephson-coupling origin, indicating a strong evidence of Josephson-coupling origin for the upward curvature of the so-called Hc2 in high Tc superconductors.
Much attention is given for the squeezed coherent states (SCS's) superposition. The s-parameterized charactristic function (CF) for the output field with the superposition of SCS's as input field is given. The s-parameterized quasiprobabilty distribution function (QDF) for the output field with superposition of SCS's as input state are investigated. Various moments are calculated by using the s-parameterized CF for that field. The Glauber second-order coherence function is calculated. The quadrature squeezing for the output field are discussed. Some QDF's of the output fields are plotted as functions of the interaction time. Phase properties of the superpostion of SCS's are studied. The s-parameterized phase distributions obtained by integrating the s-parameterized QDF over radial variable are illustrated.
In this paper, first of all, we proved if the ideal Bose gas with a finite volume and number of particles has a non-degenerate single-particle energy level. epsilon(n), the chemical potential mu can take the value mu(n) = epsilon(n) and there is a phase transition temperature T-p,T-n, where n = 0, 1, 2 Taking epsilon(0) less than or equal to epsilon(n) < (n+1), then T-p,T-0 greater than or equal to T-p,T-n > T-p,T-n+1. When the temperature T > T-p,T-n Or T less than or equal to T-p,T-n+1, mu not equal epsilon(n) and the most probable occupation number N-n = 0. In the temperature interval T-p,T-n greater than or equal to T > T-p,T-n+1, mu = epsilon(n) and 0 less than or equal to N-n = N - Sigma(j)Nj less than or similar to supN(n), where N-j is the most probable occupation number in the degenerate lever j. Thus, if the finite ideal Bose gas has some non-degenerate single-particle levels, there exists a characteristic temperature T-p = T-p,T-0. The chemical potential mu is quantized when T less than or equal to T-p, and this leads to the creation of a macroscopic quantum state (pure state) or Bose-Einstein condensation phase. T-p = T-p,T-0 is a first-order phase transition point, T-p,T-n not equal 0 is a zero-order phase transition point; Next, we obtained a new expression of the most probable distribution of the finite ideal Bose gas. In this expression N-j is directly proportional to g(j) - 1, where g(j) and N-j are, respectively the degeneracy and the most probable occupation number in the degenerate level j. This property agrees with what chemical potential can be quantized if there is a non-degenerate level for the finite ideal Bose gas. Finally, using this expression, we defined a micro-partition function M, obtained the statistical expressions of some thermodynamical quantities.
An generalized version of the Siegman formula which comes directly from Helmholtz equation is reported in this paper. Based on this formula, a comparison between the two definitions of the light beam far-field divergence angle is made. It is discovered the Siegman's moment definition for divergence angle would not make sense if the light beam could not be approximated to the slowly varying one. The proof of inequality M(2)greater than or equal to 1 given by Chen and Qiu would fail if the evanescence wave effects are considered.
Partially oriented and highly textured diamond films on Si(111) substrates were achieved by hot-filament chemical vapor deposition(HFCVD). High nucleation density greater than 5 x 10(8) cm(-2) was realized in 3 min by near-surface glow discharge. The as-grown films were characterized. by scanning electron microscopy (SEM), X-ray diffraction(XRD) and Raman spectroscopy. It was found that by adding a small amount of oxygen to the mixture of CH4/H-2, the appearance of facet(111) was well controlled, and the secondary nucleation on the facet(111) was suppressed greatly. Growth feature of homoepitaxy on diamond(111) surface was demonstrated to be in Stranski-Krastanov model by SEM.
The Hamiltonian is derived for the interaction of a Lambda-type three-level atom with a two-mode quantum cavity field from the general interaction Hamiltonian between a multi-level atom and a multi-mode radiation field, and it is reduced to an effective two-mode Raman-coupled model under a large detuning condition. We propose a modified effective Hamiltonian for the two-mode Raman-coupled model, find the time-dependent state vectors, and present the validity conditions for the involved interaction Hamiltonians. It is shown that in the study of the two-mode Raman-coupled model it is not enough to retain only the usually used effective Hamiltonian, one must also take into account the ac Stark shift of the atomic levels (at least one of the levels). Finally, we study the atomic dynamics in the interaction of a Lambda-type three-level atom with a two-mode quantum cavity field and in the two-mode Raman-coupled model. We find that the number of collapse-revivals, the collapse time and the revival time show new characteristics.
The Larmor precession of a spinning particle in a magnetic field confined in the region of one dimensional-rectangular barrier is investigated with the spin coherent state of incoming particle, which has advantage to recognize the equation of the spin precession. Our new observation is that the precession time of spin is uniquely determined and is seen to be equal to the dwell time.
Using 1+1 soliton-like polaron model of a deformable continuum, the critical temperature and the energy gap in high-temperature superconductors Y1-xCaxBa2Cu3-xMxO7-delta(M=Fe, Ni) are studied in the framework of finite temperature Green's function theory. The ratio 2 Delta/k(B)T(c)=3.9 is obtained. Theoretical results are found in good agreement with the experimental data.
Based on the Zakharov-Shabat equation of the inverse scattering transform for the unstable nonlinear Schr?dinger equation, for which a perturbation theory with corrections is developed in this paper. All necessary formulae for calculating the scattering data are derived. Based upon these formulae, the effect due to the corrections can be studied. As an example, the correction due to the damping is calculated.
This paper reports the upconversion luminescence phenomenon of crystal ErP5O14 in ultraviolet to blue-green wave range induced by red DCM dye laser. The upconversion passage of each upconversion fluorescence is confirmed. It is found that the upconversion mechanism is mainly non-resonant upconversion energy transfers between rare earth ions when laser wavelength is near 650 nm. It is very interesting that the non-resonant upconversion energy transfer is achieved directly through a kind of coupling state of rare earth ion cluster and the ions do not exchange their phonon energy with crystal lattice.
Positron lifetime spectra have been measured in two kinds of carbon nanotube powders as a function of temperature range between 32 and 296 K. It has been found that all spectra are essentially temperature-independent in the above temperature range. The results of analysis show that there are three components in the powders of carbon nanotube with an average diameter of 30 nm, and four components in the powders of carbon nanotube with typical diameters of around 15 nm. The average values of lifetime components obtained at various temperatures are about 220, 390 ps, and 2.0 ns for the former, and about 140, 300, 650 ps and 6.4 ns for the latter.
Intensity dependence of the total effective trap density N-eff is studied theoretically for the two-centre and the three-charge-state photorefractive crystals. The results show that N-eff always increases with increasing intensity in three-charge-state crystals, whereas it has more complicated behaviors in two-centre crystals. When S(D)gamma(T)/S(T)gamma(D) is Small, N-eff increases and tends to saturate with increasing intensity for both type-A and type-B two-centre crystals. When S(D)gamma(Y)/S(T)gamma(D) is large, N-eff increases to a maximum and then decreases a little for type-A crystals and decreases greatly for type-B crystals. The different intensity dependences of N-eff in the two types of crystals: come from their different level structures.
