Modern Physics Letters B

High-T_c superconductors with CuO₂ layers, manganites La_1-xSr_xMnO₃ and cobaltites LaCoO₃ present several mysteries in their physical properties. Most of them are believed to come from the strongly-correlated nature of these materials. From the theoretical viewpoint, there are many hidden rocks in making the consistent description of the band structure and low-energy physics starting from the Fermi-liquid approach. Here, we discuss the alternative method — multielectron approach to the electronic structure calculations for the Mott insulators — called LDA + GTB (local density approximation + generalized tight-binding) method. Its origin is a straightforward generalization of the Hubbard perturbation theory in the atomic limit and the multiband p-d Hamiltonian with the parameters calculated within LDA. We briefly discuss the method and focus on its applications to cuprates, manganites and cobaltites.

The molecular dynamics (MD) method is used to investigate the interaction between the 30° partial dislocation and hex-vacancy (V₆) in Si. The interaction processes are described in detail and compared with the prior results of mono-vacancy (V₁) and di-vacancy (V₂). It is found that dislocations are pinned by V₆ when the shear stresses are smaller than a definite critical value τ_c. It illustrates that the encountered two segments beside vacant sites parallel each other or annihilate. Moreover, it is shown that the critical shear stress τ_c is mainly determined by both the migration barrier of kink and the volume of vacancy. Although V₆ cannot make dislocations move faster due to the present small models, it may lower the dislocation density in certain conditions due to the pinning effect.

In this letter, asymmetric simple exclusion processes with off-ramp on the boundaries have been studied by asymmetric simple exclusion processes (ASEPs). In this model, particles can only detach from a single off-ramp on the boundaries of the system. The phase diagrams and density profiles are calculated by approximate mean field theory and have shown good agreement with the extensive Monte Carlo computer simulations.

We study the tolerance of scale-free networks (following a power-law distribution P(k) = c⋅k^α) under degree segment protection and removal. We use percolation theory to examine analytically and numerically the critical node removal fraction p_c required for the disintegration of the network as well as the critical node protection fraction p_pc necessary to immunize the network against the disintegration. We show that when degree segment protection is prior to degree segment removal and 2 ≤ α ≤3, scale-free networks are quite robust due to the extremely low value of p_pc. Meanwhile, if we protect a degree segment with a fixed fraction of nodes, the threshold p_c has a generally downward trend as the degree sum of the segment decreases, but it is not strictly monotonic.

In this paper, the Bremsstrahlung emission and re-absorption mechanisms are studied mainly through Inverse Bremsstrahlung and Compton Scattering. The Radiation Specific Power is calculated numerically assuming the suitable forms of Energy Distribution Function in plasma conditions. The calculation of Spectral Emission shows that, the Bremsstrahlung emission is strongly forward and backward peak relative to electron direction in overdense and high temperature plasma. Finally, some of the conditions for dominant of the re-absorption mechanism are explained.

We propose a scheme for concentrating an arbitrary two-particle non-maximally entangled state into a maximally entangled state assisted with three cavities. The scheme involves two interaction–detection cycles and resonant interaction between atom and cavity mode. With the help of the atom trapped in the cavity, the concentration of a two-particle non-maximally entangled state trapped in separate cavities can be realized with a certain probability according to the results of photon detectors. The important feature of our scheme is that we can realize the concentration of an arbitrary two-atom non-maximally entangled state and we do not perform Bell-state measurements.

The full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory, using the generalized gradient approximation, is used to study the structural and electronic properties of zinc-blende B_yAl_xGa_1-x-yN quaternary alloys that match the lattice of an AlN substrate. The range of compositions, for which the lattice of the alloy matches AlN, is determined. Our calculated band structure, density of states, electron density and lattice parameter for B_yAl_xGa_1-x-yN allow to accurately evaluate the profound effect that the incorporation of small amounts of Boron have on structural and electronic properties of Al_xGa_1-xN alloys. A comparison of the ground state properties with the available experimental and theoretical data is made for the compounds related to B_yAl_xGa_1-x-yN and of the Al_xGa_1-xN alloys. The results show a strong dependence of the band gap (as well as the lattice parameter) on the Boron content, which might make B_yAl_xGa_1-x-yN materials promising and useful for optoelectronic applications.

Starting with the Heisenberg Hamiltonian of the one-dimensional ferromagnetic chain in external fields, we have studied quantum characteristics of solitary waves and interactions between solitary waves and the time-varying electromagnetic field. It is shown that the energy and magnetic moments of the solitary wave are quantized. Utilizing these novel results, we have obtained the Bloch's equation of the two-level quantum solitary wave in a simple harmonic magnetic field.