International Journal of Modern Physics B

Using effective-field theory with correlations, we investigate the effects of interfacial pseudo-spin coupling fluctuations on the susceptibility and polarization of ferroelectric superlattices within the framework of transverse Ising model. It is found that the interfacial coupling fluctuations increase the susceptibility in the low temperature region. For a strong interfacial coupling, the phase transition temperature decreases with the strength of fluctuations of the interfacial coupling. The dependence of the susceptibility on the superlattice period of BaTiO₃/SrTiO₃ are plotted for different interfacial coupling fluctuations strength. At room temperature, when the interfacial coupling fluctuation increases, the peak position of the susceptibility will shift to a large superlattice period.

Numerical simulations have been used to investigate the synchronization behavior of a unidirectionally coupled pair of double-well duffing oscillators (DDOs). The DDOs were simulated in their structurally stable chaotic zone and their state variables were found to completely synchronized. The essential feature of the transition to the synchronous state is shown to correspond to a boundary crisis in which the cross-well chaotic attractor is destroyed.

The Gibbs free energy of two highly charged plates immersed in an electrolyte solution in a finite container is investigated using mean field theory. Adiabatic potential of the charged plates, which is derived from the Gibbs free energy, has a long-range weak attractive part and medium range strong repulsive part under the Dirichlet boundary condition. From comparison with the Helmholtz adiabatic potential, it is proved that the two adiabatic potentials have qualitatively the same structure of a repulsive component and an attractive component and that the Gibbs adiabatic potential shows the stronger attractive effect.

We investigate the superconducting transition temperature, T_c in the presence of the magnetic field, H in CeCoIn₅. It is shown that phonon-enhanced spin fluctuations drive this superconductivity once more as suggested by us (Phys. Rev.B61, 4289). We know the magnetic dependence of our transition temperature is in good correspondence with experimental data. It is elucidated that the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) superconducting states are closely related to the temperature gradient contributed by the external magnetic field.

In this paper, we numerically investigate the chaotic behaviors of the fractional-order Chua's circuit with a piecewise-linear nonlinearity. We find that chaos exists in the fractional-order Chua's circuit with order less than 3. The lowest order we find to have chaos is 2.7 in the homogeneous fractional-order Chua's circuit and 2.8 in the unhomogeneous fractional-order Chua's circuit. Our results are validated by the existence of a positive Lyapunov exponent. A chaos synchronization method is also presented for synchronizing the homogeneous fractional-order chaotic Chua's systems. The approach, based on stability theory of fractional-order linear systems, is simple and theoretically rigorous. It does not require the computation of the conditional Lyapunov exponents. Simulation results are used to visualize and illustrate the effectiveness of the proposed synchronization method.

We present a systematic simple method for constructing non-local quantum conditional rotation with single target and multiple targets operations. We firstly show how a non-local conditional rotation with single target operation can be implemented with unit fidelity and unit probability by using a maximally entangled pair as quantum channel. We also put forward a scheme for probabilistically implementing the operation with unit fidelity by employing a partially entangled pair as quantum channel. The required physical resources for implementation of the non-local operation in these two cases are discussed. We further consider non-local conditional rotation with multiple targets operations on N spatially distributed systems, and show that the number of possible distinct operations increases here exponentially, with the available number of entangled pairs that are initially distributed between systems. We also point out that the non-local conditional rotation operation can be used to generate multiparticle entanglement between particles belonging to distant users in a communication network and distributed quantum computer.

We report effects of heat treatments on physical properties and finding optimal heating condition to add value to Thai blue sapphires. The color of sapphire arises from the presence of trace 3d-transition ions in its crystal lattice. For blue sapphire, the color is due to a charge transfer mechanism between Fe²⁺ and Ti⁴⁺ ions. However, iron may adopt both Fe³⁺ and Fe²⁺ due to oxygen vacancies. Fe³⁺ and Fe²⁺ yield sapphire yellow and green colors, respectively. Therefore, we have to convert as many as possible of Fe³⁺ to Fe²⁺ by heating the blue sapphire in N₂ atmosphere for 12 h. Experimental results reveal that the ratio of lattice parameter c/a increases with the heating temperature and reaches maximum at 1700°C, which can be caused by displacement of Fe³⁺ ions or more Fe³⁺ ions being converted to Fe²⁺. ESR signals show that the number of Fe³⁺ ions decreases roughly linearly with the heating temperature. The intense sky blue color was achieved after the 1500°C heat treatment, having the ratio ~0.78. The optimal heat treatment should therefore be at 1500°C in flowing N₂ atmosphere for Thai blue sapphires which yield intense sky blue color and good crystal clarity. The blue sapphires exhibited good clarity but light sky blue due to the increase in lightness after the treatment at 1700°C. A monoclinic distortion of the corundum structure has been found to start at the 1600°C treatment by ESR spectrometer. This is also clearly evident from low angle shifts of XRD peaks after heating at 1700°C. We can therefore conclude that the color change of Thai blue sapphires arises from the conversion of Fe³⁺ to Fe²⁺ and thus the change in crystal field. The monoclinic distortion of the crystal structure may also play an important role in coloring the sapphires after the heat treatment at 1600–1700°C.

We examine in terms of exact solutions of the time-dependent Schrödinger equation, the quantum tunnelling process in Bose–Einstein condensates of two interacting species trapped in a double well configuration. Based on the two series of time-dependent SU(2) gauge transformations, we diagonalize the Hamilton operator and obtain analytic time-evolution formulas of the population imbalance and the berry phase. The particle population imbalance of species A between the two wells is studied analytically.

Structural changes induced by temperature rising in binary silico-bismuthate glasses are investigated by differential thermal analysis. Several exothermic peaks are recorded for all samples. Progressive substitution of Bi₂O₃ by SiO₂ contributes to the structural relaxation of vitreous network and leads to diminishing of the melting temperature, even as SiO₂ content reaches 40 mol%. Glass stability is enhanced by addition of silicon dioxide.

The effect of tube geometry on quantum transport in carbon nanotube electron resonators is studied analytically by developing a transfer matrix method. The conductance of metallic chiral nanotubes not only shows oscillating variations as a function of gate voltage with rapid and slow periods, but also exhibits a conductance gap and some resonance conductance peaks in the gap region. These features depend on to a high degree on both tube diameter and chirality and thus provide an experimental means for structure appraisal of the nanotube devices.