International Journal of Modern Physics B

The generalized Floquet approach is developed to study memory effect on electron transport phenomena through a periodically driven single quantum dot in an electrode–multi-level dot–electrode nanoscale quantum device. The memory effect is treated using a multi-function Lorentzian spectral density (LSD) model that mimics the spectral density of each electrode in terms of multiple Lorentzian functions. For the symmetric single-function LSD model involving a single-level dot, the underlying single-particle propagator is shown to be related to a 2×2 effective time-dependent Hamiltonian that includes both the periodic external field and the electrode memory effect. By invoking the generalized Van Vleck (GVV) nearly degenerate perturbation theory, an analytical Tien-Gordon-like expression is derived for arbitrary order multi-photon resonance d.c. tunneling current. Numerically converged simulations and the GVV analytical results are in good agreement, revealing the origin of multi-photon coherent destruction of tunneling and accounting for the suppression of the staircase jumps of d.c. current due to the memory effect. Specially, a novel blockade phenomenon is observed, showing distinctive oscillations in the field-induced current in the large bias voltage limit.

oActive sliding mode control is one of the effective methods to synchronize chaotic systems in the presence of uncertainties. Use of the method, however, requires decision making on how to choose the control parameters for a specific performance. In this paper we propose an algorithm to determine the best control parameters for which the minimum control efforts are required to synchronize two identical or non-identical chaotic systems. We have also determined the maximum range of the uncertainties on which the selected control parameters to work properly. The effectiveness of the proposed method has been verified through numerical simulations.

This paper proposes a new method of controlling quantum systems via probability density function (PDF) control. Based on the quantum model from the PDF perspective, two specific control algorithms are proposed for the general case and limited input energy, respectively. Unlike traditional quantum control methods, this method directly controls the probability distribution of the quantum state. It provides an alternative method for quantum control engineering.

An analysis on the chaotic dynamics of a six-dimensional nonlinear system which represents the averaged equation of an axially moving viscoelastic belt is given in this paper for the first time. We combine the theory of normal form and the global perturbation method to investigate the global bifurcations and chaotic dynamics of the axially moving viscoelastic belt. Firstly, the theory of normal form is used to reduce six-dimensional averaged equation to the simpler normal form. Then, the global perturbation method is employed to analyze the global bifurcations and chaotic dynamics of six-dimensional nonlinear system. The analysis results indicate that there exist the homoclinic bifurcations and the single-pulse in six-dimensional averaged equation. Finally, numerical simulations are also used to investigate the nonlinear dynamic characteristics of the axially moving viscoelastic belt. The results of numerical simulations demonstrate that there exist the chaotic motions and the jumping orbits of the axially moving viscoelastic belt.

In this paper, starting from a lattice model of topological insulators, we study the quantum phase transitions among different quantum states, including quantum spin Hall state, quantum anomalous Hall state and normal band insulator state by calculating their topological properties (edge states, quantized spin Hall conductivities, and the number of zero mode on a π-flux). We find that at the topological quantum phase transitions (TQPTs), the topological "order parameter" — spin Chern number will jump. And since the masses of the nodal fermions will change sign, the third derivative of ground-state energy is nonanalytic. In addition, we discuss the finite temperature properties and the stability of the TQPTs.

A Monte Carlo simulation was presented to describe the electrons and heavy particles transport behaviors in the nitrogen glow discharge which happened between the two drilled electrodes of the plasma ion source. The probability of various electron-molecule collision process, the average energy and exit angle distribution of outgoing particles were calculated in different E/N. The results showed that they followed Boltzmann distribution approximately. Along with E/N increasing, the electron and the heavy particle average energy and the probability of electric excitation, dissociation, ionization, dissociative ionization collisions were increased. Comparing to the uniform electric field distribution, the ionization rate and the electron average energy would be enhanced obviously in the nonuniform electric field.

We have used the lowest order constrained variational (LOCV) method to calculate some of the ground state properties of the polarized liquid ³He by inclusion of the three-body cluster energy contribution. It is shown that the contribution of the three-body cluster term for the ground state energy of this system is substantial, especially at high densities. It is also shown that the inclusion of the three-body energy contribution improves our result for the binding energy of the liquid ³He. It is seen that the magnitude of the three-body cluster energy decreases by increasing the polarization. The magnetic susceptibility of the liquid ³He has also been computed, showing no spontaneous ferromagnetic phase transition.

A novel measurement method of parallel-plate waveguide (PPW) system is introduced to detect the characteristics of left-handed metamaterials (LHMs). A sample of LHM composed of triangular open-loop resonator plus wire structures is proposed and measured by using this PPW system. The measurement results are in good agreement with the simulation results. Furthermore, the parametric retrieval algorithm, the calculated negative phase shift and the simulated subwavelength imaging result are given to validate the authenticity of PPW measurement system, which effectively demonstrates the measured transmission passband is indeed a left-handed passband.

Modeling and amplification of erbium–ytterbium co-doped phosphate glass waveguide amplifier with a cascaded multilayer medium thin film filter is investigated theoretically. This proposed filter consists of some different filtering unit cells with different central wavelength and bandwidth, and each cell can suppress certain peak gain at a specific wavelength. The intrinsical gain spectrum of amplifier is obtained by solving a set of rate and power propagation equations, the effect of transmittance spectrum of thin film filter on flattening gain is discussed, and the transmission function of cascaded multilayer medium thin film filter is obtained.

In He's frequency–amplitude formulation, two trial functions are chosen, which are, respectively, the solutions of linear oscillators. In this paper, an alternative choice of trial function is given: a trial function is a solution of a nonlinear oscillator whose frequency is known. The Duffing equation is used to show the effective of the method.

An electron spin resonance (ESR) study of the effects of pulverization on non-irradiated crystalline sugar was performed. It indicated that the crystalline sugar before being ground did not give any ESR signal but an ESR signal was found in pulverized sugar. These results implied that free radicals were produced by pulverization. Moreover, the free radical density increased as the particle size decreased. From high-performance liquid chromatography analysis and the ESR spectrum of non-irradiated powdered sucrose, it can be inferred that the pulverization-induced free radical in sugar is a sucrose radical. Recently, many researchers have reported that sugar irradiated with ⁶⁰Co γ-rays at different doses produced stable sucrose radicals. This may imply that the process of sucrose radical formation by mechanical stress is similar to that for irradiation.