International Journal of Modern Physics B

In order to realize the spin-polarized field-effect-transistor, a controllable spin–orbit interaction is necessary. Two kinds of spin–orbit interaction, Dresselhaus and Rashba spin–orbit interaction, in semiconductor heterostructures have been widely discussed and investigated in terms of both theories and experiments. Dresselhaus and Rashba spin–orbit interaction mainly comes from the lack of inversion symmetry and effective electric field inside the quantum well, respectively. Many experimental investigations show that external voltages affect the carrier concentration of reservoirs, wavefunction distribution in the quantum well and the conduction band profile of the heterostructures. The details of the mechanisms and the efficiency of different effects on the spin–orbit interaction intensity are discussed through different structures and materials. The results show that an increase in carrier concentration or a decrease in gate voltage enhances the Rashba spin–orbit interaction intensity. On the other hand, the wavefunction penetration is the other important mechanism that affects the Rashba spin–orbit interaction intensity. The carrier concentration asymmetry factor strongly affects the efficiency of the external gate voltage on the Rashba spin–orbit interaction intensity.

The phenomenon of stochastic resonance (SR) in a time-delayed bistable system with colored coupling between multiplicative and additive noise terms is investigated. The SR can be induced by the multiplicative noise, the time delay and the coupling strength between noise terms. Meanwhile, the SR is affected by the initial condition of the system.

We study the one-dimensional double-exchange model with L localized spins and one mobile electron. We solve the Schrödinger equation analytically and obtain the energies and wavefunctions for all the eigenstates with spin S = (l-1)/2 exactly. As an application, we compute the single-particle Green's function. We show that, for vanishing exchange interactions between localized spins, the single-particle spectrum is entirely incoherent and the lowest band has an infinite band mass, i.e., the single electron is localized due to its interaction with the spin excitations. For nonvanishing exchange interactions between localized spins, the lower edge of the spectrum acquires a dispersion but the spectrum remains incoherent with no well-defined quasiparticle peak.

Based on the elasticity energy, a magnetic nanowire suspended in a half-space twisted nematic liquid crystal (TNLC) was studied. Using equivalent capacitance, the equilibrium position of the nanowire, the deflexion of its axis from the anchoring direction and the eigenfrequency of the nanowire around its equilibrium position were calculated. The results show that the height of the nanowire increases slowly with increasing H in small magnetic field regime less than 0.01 Gs, and picks up quickly if H is larger than about 0.02 Gs. A calculation of the eigenfrequency of the nanowire shows that it decreases quickly with the increase of H at small magnetic field regime and then levels off towards a lower limit, which is about 170 Hz based on the present parameters under larger field. Moreover, the eigenfrequency also depends on mass with a maximum value which is found to be field-independent when the external field is large enough.

Zinc oxide films were deposited on silicon substrates by reactive pulsed laser deposition of zinc target. The effect of substrate temperatures on the crystal and band edge luminescence was studied using X-ray diffraction, scanning electron microscopy and Raman spectra. All the films deposited in the substrate temperatures range from room temperature to 600°C exhibited strong c-axis orientation. The preferred orientation of crystal changed with substrate temperature increase, due to the preferential nucleation at lower temperatures and surface diffusion at higher temperatures. The detailed micro-structural analysis indicated a tensile stress in all the films using X-ray diffraction and Raman spectra. It is interesting that the film deposited at 350°C, which exhibited best crystallinity quality in the X-ray diffraction, rocking curve and the best stoichiometry, less defects in Raman spectra, does not show the most intense UV emission and weakest visible emission. The most intense UV emission was exhibited in the films deposited at 500°C which had the equiaxed grain size.

Based on the coordinate transformation method, we derived the material parameters for arbitrary N-sided regular polygonal transparent device, which is an important device for antenna protection. The electric field distributions of the device under TE wave and cylindrical wave irradiation are simulated using the finite element solver COMSOL Multiphysics. It shows that although the incident waves are distorted in the transformation region, they return to the original wavefronts when passing through the transformation region. The results of full-wave simulations validate the material parameters for the N-sided regular polygonal transparent device we derived.

In a partially blind signature scheme, the signer explicitly includes pre-agreed common information in the blind signature, which can improve the availability and performance. We present a new partially blind signature scheme based on fundamental properties of quantum mechanics. In addition, we analyze the security of this scheme, and show it is not possible to forge valid partially blind signatures. Moreover, the comparisons between this scheme and those based on public-key cryptography are also discussed.

The modulational instability (MI) of Bose–Einstein condensates based on a modified Gross–Pitaevskii equation (GPE) which takes into account quantum fluctuations and a shape-dependent term, trapped in an external time-dependent complex potential is investigated. The external potential consists of an expulsive parabolic background with a complex potential and a gravitational field. The theoretical analysis uses a modified lens-type transformation which converts the modified GPE into a modified form without an explicit spatial dependence. A MI criterion and a growth rate are explicitly derived, both taking into account quantum fluctuations and the parameter related to the feeding or loss of atoms in the condensate which significantly affect the gain of instability of the condensate. Direct numerical simulations of the modified GPE show convincing agreements with analytical predictions. In addition, our numerical results also reveal that the gravitational field has three effects on the MI: (i) the deviation backward or forward of solitons trains, (ii) the enhancement of the appearance of the MI and (iii) the reduction of the lifetime of pulses. Moreover, numerical simulations proved that it is possible to control the propagation of the generated solitons trains by a proper choice of parameters characterizing both the loss or feeding of atoms and the gravitational field, respectively.

In this paper, the concepts of the photon escape probability and the transmission factor are reviewed and the photon escape probabilities for infinite plane-parallel slab and spherical geometries are discussed. The photon escape probabilities using the transmission factor, for Lorentzian profile and Holtsmarkian profile, are discussed. Finally, the photon escape probabilities we calculated are compared with that calculated using before method for Lorentzian profile and Holtsmarkian profile, and some useful conclusions are drawn.

In this paper, a nonlinear state observer control strategy is developed for projective self-synchronization of the fractional-order chaotic attractors of a permanent magnet synchronous motor (PMSM) system. The mathematical model of PMSM system in a smooth fractional-order form is derived by using the fractional derivative theory. A state observer control design can achieve the full-state projective synchronization of the fractional-order PMSM (FO-PMSM) system without the limitation of partial-linearity. Global stability and asymptotic synchronization between the outputs of drive system and response system can be obtained. Simulation results are provided to demonstrate the effectiveness of the approach.

Within the limits of the uniform approach with the assistance of the vacancy mechanism the description of melting and surface roughening of both free nanoparticles and nanoparticles deposited on the surface of solid body under conditions of thermodynamic equilibrium is offered. Surface roughening of a spherical particle is represented as a phase transition in vacancy subsystem, in which supersaturation is formed by reducing the particle size. It is shown that interaction between vacancies result in to the unification of vacancies on a surface in vacancy clusters, that can be regarded as the appearance of a surface roughness of nanoparticles. It is shown that increasing concentration of vacancies caused by the modification of effective vacancy formation energy with decreasing sizes of nanoparticles result into a modification of shear modulus of material. By vanishing the shear modulus (Born criteria of melting) the dependence of temperature of fusion of nanoparticles of different metals on radius was determined.

This study describes structural, electronic and optical properties of Mg_xCd_1-xX (X = S, Se, Te) alloys in the complete range 0≤x ≤1 of composition x in the zinc-blende (ZB) phase with the help of full-potential linearized augmented plane wave plus local orbitals (FP-LAPW+lo) method within density functional theory (DFT). In order to calculate total energy, generalized gradient approximation (Wu–Cohen GGA) has been applied, which is based on optimization energy. For electronic structure calculations, the corresponding potential is being optimized by Engel–Vosko GGA formalism. Our calculations reveal the nonlinear variation of lattice constant and bulk modulus with different concentration for the end binary and their ternary alloys, which slightly deviates from Vegard's law. The calculated band structures show a direct band gap for all three alloys with increasing order in the complete range of the compositional parameter x. In addition, we have discussed the disorder parameter (gap bowing) and concluded that the total band gap bowing is substantially influenced by the chemical (electronegativity) contribution. The calculated density of states (DOS) of these alloys is discussed in terms of contribution from various s-, p- and d-states of the constituent atoms and charge density distributions plots are analyzed. Optical properties have been presented in the form of the complex dielectric function ε(ω), refractive index n(ω) and extinction coefficient k(ω) as function of the incident photon energy, and the results have been compared with existing experimental data and other theoretical calculations.

Synchronization is a powerful basic rule in nature that regulates a large variety of complex processes, and global synchronization phenomena have been extensively studied for modeling and analyzing the dynamic of systems. Distinct from the existing studies, the work presented here explores the notion of local synchronization phenomenon and their intrinsic properties from the dynamics of a stochastic model defined on a complex network. The relationship between the hierarchical community structure of the network and the local synchronization properties of such a stochastic model has been established based on the famous Kuramoto Model. Critical topological information regarding to the community structures of the network can be inferred from their spectral signatures. Utilizing a novel dynamic system, we have developed an efficient two stages model which can efficiently uncover natural communities hidden in networks in a scalable manner. The effectiveness and efficiency of the algorithm have been theoretically analyzed as well as experimentally validated and it overcomes the inefficiency of the existing methods.

In this paper, we investigate the fractal pattern in spatial structure of urban road networks. By introducing sub-domain, an improved box-counting algorithm is proposed to obtain the fractal pattern. Numerical experiments explore the realistic urban road network at Dalian city in China. In order to clearly show the performance of our proposed box-counting algorithm, two other measures for urban road networks, i.e., density pattern and accessibility pattern are introduced, compared and discussed.

In this paper, an image encryption algorithm based on couple multiple chaotic systems is presented. It made the one-dimensional Coupled Map Lattice (CML) formed by Skew Tent map as spatiotemporal chaotic system and made its output sequence as the initial value of logistic and meanwhile did iterative of specific times to get the final key sequence, and then did XOR operations with corresponding pixels to finish the encryption. Numerical analysis expresses that this algorithm has large enough space and high security.

Based on the stability theory of fractional order systems and the pole placement technique, this paper designs a synchronization scheme with the state observer method and achieves the projective synchronization of a class of fractional order chaotic systems. Taking an example for the fractional order unified system by using this observer controller, and numerical simulations of fractional order Lorenz-like system, fractional order Lü system and fractional order Chen system are provided to demonstrate the effectiveness of the proposed scheme.

In this letter, hierarchies of super Kaup–Newell equation are derived, including positive nonisospectral and negative nonisospectral super Kaup–Newell hierarchy, the integrable coupling positive nonisospectral and negative nonisospectral super Kaup–Newell hierarchy.

The properties of a strong-coupled bound magnetopolaron in an asymmetric quantum dot (QD) have been investigated by using the Tokuda modified linear combination operator and the unitary transformation methods on the basis of the Huybrechts' strong-coupled model. We derive the expressions of the ground-state energy as function of the transverse and longitudinal confinement lengths, the magnetic field. Numerical calculation is performed and the results show that the ground-state energy of the bound magnetopolaron splits into two branches, taking into account the spin influences. And the ground-state energy decreases with increasing the transverse and longitudinal confinement lengths and increases with the rising of the magnetic field.