International Journal of Modern Physics B

We investigate the interaction of a two-level atom with a cavity field in a squeezed displaced number state: . It is shown that this state exhibits interesting features, while generalizing various particular results of the literature. Additional discussions about the influence of phase optimization of a state upon collapse and revivals effects are also considered.

The binding energies of excitons in finite barrier quantum wells under hydrostatic pressure are calculated by a variational method. The influences of hydrostatic pressure on the effective masses of the electron and hole, the dielectric constant, and the conduction band offset between the well and barriers are taken into account in the calculation. The numerical results for the GaAs/Al_xGa_1-xAs and GaN/Al_xGa_1-xN quantum wells are given respectively. It is shown that the exciton binding energy increases linearly with the pressure and the pressure effect on arsenide quantum wells is more obvious than that on nitride ones. The exciton binding energies monotonically increase with increasing barrier height, which is related to the Al concentration of the barriers and the influence of the pressure.

A family of new discrete nonlinear equations associated with the Lotka–Volterra lattice is constructed by defining a novel algebraic system X. Moreover, some properties of the hierarchy are discussed. Furthermore, nonlinear integrable couplings of the resulting hierarchy are derived from an extended algebraic system . Finally, an example is given.

The size influence of silica microspheres on the photonic band gap (PBG) of three-dimensional face-centered-cubic (fcc) photonic crystals (PCs) is studied by means of colloidal photonic crystals, which are self-assembled by the vertical deposition technique. Monodispersed SiO₂ microspheres with a diameter of 220–320 nm are synthesized using tetraethylorthosilicate (TEOS) as a precursor material. We find that the PBG of the PCs shifts from 450 nm to 680 nm with silica spheres increasing from 220 to 320 nm. In addition, the PBG moves to higher photon energy when the samples are annealed in a temperature range of 200–700°C. The large shift results from the decrease in refraction index of silica due to moisture evaporation.

We propose an alternative scheme to generate the GHZ states and cluster states for many trapped ions illuminated by a single laser tuned to the first lower vibrational sideband. The distinct advantage of the present scheme is that it does not use the vibrational mode as the data bus and only requires a single resonant interaction. Thus the present scheme is very simple and the interaction time is very short, which is important in view of decoherence.

Since the Goos-Hänchen (GH) effect is the displacement of the totally reflected beam at a dielectric interface from the position prediction by geometrical reflection, the concept of GH displacement is applicable only when the reflected beam retains the shape of the geometrically reflected or incident beam. The necessary and sufficient condition has been advanced for the totally reflected beam to retain the shape of the incident beam. Numerical simulations have been performed to confirm this condition. It has been shown that the GH displacement results from the mechanism of beam reshaping due to the linear dependence of the reflection phase shift upon the parallel component of the wave vector, in the interval in which the angular spectral distribution function of the incident beam is appreciable.

The electronic structure of MgB₂ with different lattice parameters, which represents the influence of pressure, has been studied from HF calculation. It has been found that the density of states at the Fermi level decreases with the decrease in lattice constant, which implies that the pressure can reduce the superconductivity of MgB₂. It was also found that more electrons are introduced from the Mg layer to the B layer with increasing pressure, resulting in the number of holes on the B layer being reduced, thus reducing superconductivity. The electron density population at different pressures clearly shows that the triangle-shaped electron distribution in the B plane, extended along the B–B bonds, indicates the typical sp² orbitals. On the other hand, there is no covalency feature between Mg and B atoms, indicating the ionic bonding property between Mg and B layers.

We propose a scheme for entanglement swapping and entanglement concentration without joint measurement by using the two-photon Jaynes-Cummings model. In the scheme, we can generate a maximally entangled pair between two initially uncorrelated atoms or cavities. Furthermore, the entangled state between two cavities is found to be a photon entanglement of two photons in one cavity and zero in another cavity.

In order to further explore the mechanism responsible for weighted complex networks, we introduce a new model that incorporates the network topology and the weights' dynamical evolutions. Our model can capture the details of weight dynamics caused not only by the addition of a new node with new links and new links between old nodes, but also the deletion of old links. We calculate analytically the distributions of both degree and strength and found that all these distributions show scale-free behavior, as confirmed in many real networks. Thus our model characterizes the real weighted complex networks more precisely.