International Journal of Modern Physics B

A Kronig–Penney model with short-range correlated impurities is used to investigate the electronic transport properties of one-dimensional disordered systems simulating both superlattices, protein chains, and polymers. Physical magnitudes characterizing the electronic charge transfer are analytically the transmission coefficient and the localization length. It is shown that a set of delocalized states occurs at particular well-defined energies. The divergence of the localization length is investigated and a critical exponent 1 is found for the barrier case which differs with the results of literature. These results support the idea that the nature of the extended states depend on the typical nature of the correlation in disorder. On this basis, the conductance of disordered superlattices is investigated as well as the relative fluctuations of the transmission coefficient.

A system of a two level atom interacting with a multi-photon single mode of electromagnetic field and damped with a phase reservoir is considered. The squeezed coherent state is taken as initial field state. The exact solution of the master equation in the case of a high-Q cavity is found. The effects of phase damping on the temporal evolution of some quantitative entanglement measures between the states of the system are investigated.

In this paper, the (2+1)-dimensional Sawada-Kotera equation is studied by the truncated Painlevé expansion and Hirota bilinear method. Firstly, based on the truncation of the Painlevé series we obtain two distinct transformations which can transform the (2+1)-dimensional Sawada-Kotera equation into two bilinear equations of different forms (which are shown to be equivalent). Then employing Hirota bilinear method, we derive the analytic one-, two- and three-soliton solutions for the bilinear equations via symbolic computation. A formula which denotes the N-soliton solution is given simultaneously. At last, the evolutions and interactions of the multi-soliton solutions are graphically discussed as well. It is worthy to be noted that the truncated Painlevé expansion provides a useful dependent variable transformation which transforms a partial differential equation into its bilinear form and by means of the bilinear form, further study of the original partial differential equation can be conducted.

The electrical magnetoconductivity near the superconducting transition in granular samples of Y_0.95Tb_0.05Ba₂Cu₃ O_7-δ was experimentally studied. The measurements were performed using low magnetic fields up to 50 Oe, applied parallel to the current. Results showed that the transition proceeds in two stages as seen by the temperature derivative of the resistivity near T_C. The analysis of the conductivity in the normal phase has evidenced contributions from Gaussian and critical fluctuations. In the regime of near zero resistance state, the occurrence of a coherence transition was evidenced, which was related to the connective nature of the granular samples. We have obtained the field independent exponents λ_C = 4.6 ± 1.1 and λ_C ≅ 6.7 ± 0.7 for fluctuation conductivity in the coherence transition.

First-principles calculations have been performed to investigate the electronic structure and ground-state properties of alkali-metal Selenides (M₂Se) and Tellurides (M₂Te)[M: Li, Na, K] using the Tight-Binding Linear Muffin-Tin Orbital (TB-LMTO) method. The exchange correlation energy is described within the local density approximation (LDA) using the von Barth and Hedin parameterization scheme. At ambient conditions, these compounds are found to crystallize in the face center cubic antifluorite (anti-CaF₂-type) structure. Ground-state properties such as total energy, equilibrium lattice parameter, and bulk modulus are calculated for these compounds. The calculated equilibrium lattice parameter is in agreement with experimental result. From the electronic structure calculations, we find that Li₂Se, Li₂Te, K₂Se, and K₂Te are indirect bandgap semiconductors, whereas Na₂Se and Na₂Te are direct bandgap semiconductors. The present results are compared with the earlier results of series of alkali-metal sulfides (M₂S) and alkali-metal oxides (M₂O), allowing us to make predictions about the total energy, bulk modulus, valence-band width, and bandgap behavior of the rest of the alkali-chalcogenide crystals.

The single-phase samples of Y_0.9Ca_0.1Ba_2-yLa_yCu₃O_z and Y_1-xCa_xBa_1.5La_0.5Cu₃O_z were synthesized with both x and y from 0 to 0.5, respectively. Structural and superconducting properties have been investigated by X-ray diffraction, Rietveld refinement, and DC magnetization measurement, respectively. Different from the self-compensating compound of Y_1-xCa_xBa_2-xLa_xCu₃O_z, carriers in these two systems of Y_1-xCa_xBa_2-yLa_yCu₃O_z are not compensated as x ≠ y. By careful study of the chemical bond lengths related to Cu(2)–O plane and Cu(1)–O chain, it is demonstrated that the critical temperature (T_c) changes monotonously with the bond lengths of Cu(1)–O(4) and Cu(2)–O(4). The analysis demonstrates that crystalline structure is one of the important factors to high-T_c superconductivity, and its influence is independent of the carrier concentration.

The Wigner distribution function (WDF) for the time-dependent quadratic Hamiltonian system is investigated in the squeezed Schrödinger cat states with the use of Lewis–Riesenfeld theory of invariants. The nonclassical aspects of the system produced by superposition of two distinct squeezed states are analyzed with emphasis on their application into special systems beyond simple harmonic oscillator. An application of our development to the measurement of quantum state by reconstructing the WDF via Autler–Townes spectroscopy is addressed. In addition, we considered particular models such as Cadirola–Kanai oscillator, frequency stable damped harmonic oscillator, and harmonic oscillator with time-variable frequency as practical applications with the object of promoting the understanding of nonclassical effects associated with the WDF.

By using a transfer matrix model, we examined in this paper the extended states of a noninteracting electron in one-dimensional dimer/trimer randomly placed in superlattices (SLs). We study numerically the effects of short-range correlated disorder on the electronic transport properties and intentionally disordered GaAs/Al_xGa_1-xAs SLs. We consider layers having identical thickness where the Al concentration x takes at random two different values with the constraint that one of them appears only in pairs or triply i.e., the random dimer/trimer barrier.

A mixed lyotropic liquid crystalline phase was observed in cationic surfactant (cetyl pyridinium chloride) with increasing concentration in polar solvent (ethylene glycol) at lower surfactant concentration (< 40 wt%). However, at intermediate concentrations, the system exhibits single phase. Morphological, thermal, and structural characterizations of these materials support our observations.

Limitations caused by degeneration of dynamics characteristics may exist in the traditional single chaotic system. The authors propose a method i.e., switch controller chaos and pseudo random bit generator (it is called SCS-PRBG for short), which is based on multiple chaotic systems and switch control. By the theoretic analysis of random key stream and performance of SCS-PRBG, we can see that its digital stream cipher has better randomicity and security. And if using hardware parallel computation, the speed of encryption can be improved sharply. The results of the experiments also present better security of this arithmetic.