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In this paper, the metal rubber and rubber were systematically compared, on the basis of comprehensive comparison of the manufacturing technique property of the metal rubber and high polymer rubber, the physical and mechanical properties of the two materials, especially the elastic and damping properties, were emphasisly compared. Finally, the scope of application of the two materials was discussed. The results of this study has certain guiding significance for application of metal rubber properly by the researchers engaged in the vibration isolation and damping of engineering.

In the present paper, we investigate the existence of ferromagnetism in a two-band Hubbard model, by applying a recently-introduced method by us to study ferromagnetism in metallic clusters. We prove rigorously that the ground state of this model is ferromagnetic if the intra-orbital Coulomb repulsion between electrons is infinitely strong and only one hole exists in the system. Our theorem improves a previous result. Furthermore, our method can also be applied to deal with the case of multiple holes.

Bipartite entanglement, entanglement spectrum, and Schmidt gap in S=1 bond-alternative antiferromagnetic Heisenberg chain are investigated by the infinite time-evolving block decimation (iTEBD) method. The quantum phase transition (QPT) from the singlet-dimer phase to the Haldane phase can be detected by the singular behavior of bipartite entanglement, the sudden change of the entanglement spectrum, and the completely vanishing of the Schmidt gap. The critical point is determined to be around rc 0.587, and the second-order character of the QPT is verified. Doubly degenerate entanglement spectra of both even and odd bonds are observed in the Haldane phase, by which one can distinguish the Haldane phase from the singlet-dimer phase easily. Nearest-neighbor antiferromagnetic correlations and next-nearest-neighbor ferromagnetic correlations are found in the whole parameter region. At the critical massless point, although exponentially decaying antiferromagnetic correlation is observed, it approaches to a constant value finally. Therefore, long-range correlations exist and the correlation length becomes divergent at the critical point.

In the present paper, by applying the Lang–Firsov canonical transformation and the so-called non-crossing approximation technique, we investigate the joint effects of the electron-phonon interaction and an external alternating gate voltage on the transport of a quantum dot system in the Kondo regime. We find that, while the satellite Kondo resonant peaks appear in both the averaged local density of states and the differential conductance, the main Kondo peak at the Fermi energy is greatly suppressed. These results confirm the previous ones derived by other methods, such as the equation of motion solution. Furthermore, based on the picture of virtual transition between quasi-eigenstates in the system, we also give a slightly different explanation on these phenomena.

In the present paper, we investigate the quantum phase transition in a spatially anisotropic antiferromagnetic Heisenberg model of S = 1 with single-ion energy anisotropy. By using the Schwinger boson representation, we calculate the Gaussian correction to the critical value J⊥c caused by quantum spin fluctuations. We find that, for the positive single-ion energy, a nonzero value of J⊥c is always needed to stabilize the antiferromagnetic long-range order in this model. It resolves a difference among literature and shows clearly that the effect of quantum fluctuations may qualitatively change a result obtained by the mean-field theories on lower-dimensional systems.

In the present paper, we calculate the Gaussian correction to the critical value J⊥c caused by quantum spin fluctuation in a two-dimensional spatially anisotropic Heisenberg antiferromagnet with integer spin S. Previously, some authors computed this quantity by the mean-field theory based on the Schwinger boson representation of spin operators. However, for S = 1, their result is much less than the one derived by numerical calculations. By taking the effect of quantum spin fluctuation into consideration, we are able to produce a greatly improved result.

In the present paper, we study the effect of van Hove singularities of conduction electron on the transport of a single quantum dot system in the Kondo regime. By using both the equation-of-motion and the noncrossing approximation techniques, we show that the corrections caused by these singularities are actually minor. It can be explained by observing that the singularities in the equations, which determine the electronic DOS on the dot, are integrable. Furthermore, we find that, although each line width function is divergent at van Hove singular points, the total divergence is canceled out in the final formula to calculate the current through the system. Therefore, as far as the qualitative properties of the system is concerned, these singularities can be ignored and the wide-band approximation can be safely used in calculation.

In the present paper, we continue our investigation on the antiferromagnetic origin of the charge order observed in the half-doped manganese. By introducing a Su–Schrieffer–Heeger (SSH) type of perturbation interaction to the double-exchange Hamiltonian, we calculate again its ground-state phase diagram at filling x = 0.5 by the unrestricted real-space Hartree–Fock approximation method. We find that, as the SSH electron-phonon interaction increases, the charge order parameter decreases to zero rapidly but the CE-type antiferromagnetic order becomes more stable. In other words, the charge order is much more fragile than the CE-type or the Neel-type antiferromagnetic orders under the electron-phonon perturbation. These results support the proposed theory in the recent publications that the charge order in these systems is induced by the antiferromagnetic correlations.

We propose a simple swarm model to study collective behaviour of a group of mobile autonomous agents interacting through a long range attraction and short range repulsion function. It is shown that the individuals (agents) will aggregate and eventually form a cohesive cluster of finite size around the swarm centre in a finite time, and the size depends only on the parameters of the swarm model. Furthermore, it is also shown that all the individuals will converge to equilibrium positions of the swarm model, and thus the configuration of the swarm converges to a constant constellation. Numerical simulations are also worked out to illustrate the analytical results.

In the present paper, we study the zero-temperature phase diagram of the doped perovskite manganites at filling by the real-space Hartree-Fock approximation method. Our purpose is to resolve a controversial issue arising recently on the origin of the charge ordered phases in these systems. We find that the antiferromagnetic superexchange interaction between the localized spins plays the central role in producing the concerned phases. Our results confirm some speculations on this issue.

We study the antiferromagnetic phase transition in the quasi-two-dimensional Hubbard model at half filling for a wide range of the Coulomb interaction U. By using the fluctuation-exchange approximation, we calculate the Neel transition temperature of the system as a function of the Coulomb interaction U. For weak-to-intermediate Coulomb interactions, the present calculation provides a reasonable result for the Neel temperature.

In this paper, by applying a simplified version of Lieb's spin-reflection-positivity method, which was recently developed by one of us [G.S. Tian and J.G. Wang, J. Phys. A: Math. Gen. 35 (2002) 941], we investigate some general properties of the boson-fermion Hamiltonian, which has been widely used as a phenomenological model to describe the real-space pairing of electrons. On a mathematically rigorous basis, we prove that for either negative or positive coupling V, which represents the spontaneous decay and recombination process between boson and fermion in the model, the pairing energy of electrons is nonzero. Furthermore, we also show that the spin-excitation gap of the boson-fermion Hamiltonian is always larger than its charged gap, as predicted by the pre-paired electron theory.

By using either numerical calculations or analytical methods, such as the bosonization technique, the ground state of the Penson–Kolb model has been previously studied by several groups. Some physicists argued that, as far as the existence of superconductivity in this model is concerned, it is canonically equivalent to the negative-U Hubbard model. However, others did not agree. In the present paper, we shall investigate this model by an independent and rigorous approach. We show that the ground state of the Penson–Kolb model is nondegenerate and has a nonvanishing overlap with the ground state of the negative-U Hubbard model. Furthermore, we also show that the ground states of both the models have the same good quantum numbers and may have superconducting long-range order at the same momentum q = 0. Our results support the equivalence between these models.

We study the effects of the energy band structure of conduction-electron on the transport properties of an interacting quantum dot system. By applying the nonequilibrium Keldysh Green function technique, we show that the finite width of electron band in leads causes the negative differential conductance in some regions of the applied voltage. We also show that the van Hove singularities in the density of states of conduction-electron do not qualitatively change the differential conductance of the system, and hence can be safely ignored. Therefore, the wide band approximation used in the previous investigations is partially justified.

We extend a previous result of ours [G.S. Tian, Phys. Rev. B63 (2001) 224413] on the antiferromagnetic spin correlations in the half-filled Hubbard model at finite temperature to the double-exchange model. To overcome the mathematical difficulty caused by the localized spin freedom in this model, we apply both Zener's argument and the finite-temperature spin-reflection-positivity method to show rigorously that, at any temperature , the spin correlations in the half-filled double-exchange model are predominantly antiferromagnetic. This conclusion is completely consistent with the experimental observations and the previous theoretical results by approximate methods.

By applying the path-integral formulation and the Feynman theorem, we calculate the off-diagonal superconducting correlation in an ultrasmall metallic grain. Unlike its behavior in the bulk limit, we find that this correlation function is an intensive quantity in this case. Therefore, superconductivity is indeed completely suppressed by quantum fluctuations as the diameter of the grain shrinks to the nanometer scale. This conclusion confirms the previous results by numerical calculations. Furthermore, it also imposes a strong constraint on the delocalizing amplitude of the pair-mixing function, which was recently proposed to characterize superconductivity in the canonical ensemble.

In this paper, the fabrication of a large cone angle near-field optical fibre probe, using the two-step chemical etching method and bent probe, is introduced and the controlling parameters of the coated Cr-Al film at the probe tip are presented. The scanning electron microscopy images display that the tip diameter of the uncoated large cone angle fibre probe obtained is less than 50nm, the cone angle over 90° and the diameter of light aperture at the coated probe tip is less than 100nm. The measured results of the optical transmission efficiency for various probe tips show that the uncoated straight optical fibre probe, film-coated straight probe and film-coated bent probe are 3×10-1, 2×10-3 and 1×10-4 times that of the flat fibre probe, respectively. In addition, the force images and near-field optical images of a standard sample are acquired using a large cone angle and film-coated bent probe.

We extend a previous result of ours [G.S. Tian, Phys. Rev. B58 (1998) 76121 on the charged gap and the spin-excitation gap of the half-filled Kondo lattice model to the doubleexchange model. In our original approach, this model cannot be dealt with since its localized spins have a large spin number S=3/2. By following a construction argument due to Zener and rewriting the double-exchange Hamiltonian, we are able to overcome this difficulty and re-establish the same relation for this model.

Based on a model Hamiltonian with the nearest-neighbor Coulomb interaction of the itinerant e(g) electrons, we investigated the possibility of the coexistence of the charge-ordering phase and the antiferromagnetic phase for the manganites R(1-x)A(x)MnO(3) with the doping of x = 0.5. Three different types of the magnetic configurations (GE-type antiferromagnetism, simple antiferromagnetism, and ferromagnetism) have been compared by numerical calculation under the mean-field approximation. We found that the charge-ordering phase may coexist with the CE-type antiferromagnetic phase if the nearest-neighbor Coulomb interaction exceeding a certain critical value.

TiO2 thin films are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for 4h, the spectra and XRD patterns of the TiO2 thin film are obtained. Weak absorption of coatings is measured by the surface thermal lensing technique, and laser-induced damage threshold (LIDT) is determined. It is found that with the increasing annealing temperature, the transmittance of TiO2 films decreases. Especially when coatings are annealed at high temperature over 1173K, the optical loss is very serious. Weak absorption detection indicates that the absorption of coatings decreases firstly and then increases, and the absorption and defects play major roles in the LIDT of TiO2 thin films.

TiO2 coatings are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for four hours, the spectra and XRD patterns of TiO2 thin film are obtained. XRD patterns reveal that only anatase phase can be observed in TiO2 coatings regardless of the different annealing temperatures, and with the increasing annealing temperature, the grain size gradually increases. The relationship between the energy gap and microstructure of anatase is determined and discussed. The quantum confinement effect is observed that with the increasing grain size of TiO2 thin film, the band gap energy shifts from 3.4 eV to 3.21 eV. Moreover, other possible influence of the TiO2 thin-film microstructure, such as surface roughness and thin film absorption, on band gap energy is also expected.

Superionic conductor RbAg4I5 crystalline grain films were prepared by vacuum thermal evaporation on NaCl crystalline substrates. The surface morphology, microstructure and the electronic energy states of the films were examined by atomic force microscopy, transmission-electron microscopy, x-ray diffraction and x-ray photoelectron spectroscopy. The results show that the obtained RbAg4I5 layer has an epitaxial film of perfect crystalline structure, and the unit cell of crystalline grain RbAg4I5 films belongs to cubic crystal system. The principal x-ray diffraction peaks at d = 3.7447 and 1.8733 A are related to the structure of ternary compound RbAg4I5 films.

The absorption spectra of the A1 low-frequency exciton band in quaternary compound Rb0.5Cs0.5Ag4I5 thin films have been measured by an UV-2100 spectrophotometer at the temperature (T) range from 78 to 289 K. The measurements at intermediate temperatures are performed within an interval of photon energies from 3.44 to 3.70 eV. The spectra have been computer-processed to separate the A1 band from the interband absorption edges, and to determine their parameters: the spectral peak position (Em), the half-width (G) of the exciton band, and the Gaussian shape ratio in the spectrum. The results show that at T 107 K, dEm/dT = -3.01×10-4 eVK-1, dG/dT = 5.47×10-4 eVK-1. It is emphasized that the phase transition γ→β in this material is carried out at a temperature of 107 K.

In this paper, a one-dimensional short-ranged spin-glass model in a random magnetic field is studied. Noticing convexity of the partition function, we use Jensen's inequality to obtain a lower bound to the averaged free energy density and the slope inequality for an upper bound. These bounds are derived under very general conditions and they can be used as tests for various approximate methods such as the replica method.

Various ionizing radiations, such as electrons and alpha particles, transfer their energy to media by produced secondary electrons and induce double- or single-strand break of DNA, which result in variable effects. To understand how the ionizing radiations interact with DNA and break it, several models have been developed, most of them consider the water as a vapor state. Actually, the ionizing particles interact with DNA which is solved in liquid water. To compare the difference of vapor and liquid water models, we calculate the stopping power, continuous slowing down approximation (CSDA) range and S value of electrons and alpha particles at cellular scale in liquid and vapor by Monte Carlo simulations, respectively. Our data show that the stopping power and CSDA range are different in liquid and vapor water in a special energy range. For many S values, the liquid model is better than the vapor model when the energy of the electrons is higher than 100 keV and the vapor model is higher than the liquid model for the 1 MeV alpha particles.

This paper studies a spin ladder model which possesses frustrating interactions. By using both the bosonization and the density matrix renormalization group techniques, it shows that the intermediate columnar dimerized phase, which exists in a narrow parameter region of the so-called J1 – J2 model, vanishes if the interchain frustration is weak and anisotropic. Therefore, it concludes that the frustrating interaction indeed plays an important role in producing such a phase. As a complementary to our previous investigation, it reaches a more complete picture of the quantum phase transition in the frustrated spin ladder systems.

Coherent electronic transport properties of silver–C60–silver molecular junctions in different configurations are studied using hybrid density function theory. The experimentally measured current flows of C60 molecules adsorbed on the silver surface are well reproduced by theoretical calculations. It is found that the current–voltage characteristics of the molecular junctions depend strongly on the configurations of the junctions. Transmission spectra combined with density of states can help us to understand in depth the transport properties. Different kinds of electrode construction are also discussed. With the help of the calculation, two possible configurations of silver–C60–silver molecular junctions are suggested.