International Journal of Modern Physics B

Fluctuation theorems establish deep relations between observables away from thermal equilibrium. Until recently, the research on fluctuation theorems was focused on time-reversal-invariant systems. In this review we address some newly discovered fluctuation relations that hold without the time-reversal symmetry, in particular, in the presence of an external magnetic field. One family of relations connects nonlinear transport coefficients in the opposite magnetic fields. Another family relates currents and noises at a fixed direction of the magnetic field in chiral systems, such as the edges of some quantum Hall liquids. We review the recent experimental and theoretical research, including the controversy about the microreversibility without the time-reversal symmetry, consider the applications of fluctuation theorems to the physics of topological states of matter, and discuss open problems.

We propose a structure of 2D photonic crystal waveguide composed of hexagonal lattices of air holes in high index materials. Frozen mode regime can be observed within the photonic band gap. Light incident into the waveguide is coupled into two modes. One mode has enhanced amplitude and the other one has slow group velocity. Finite-different time-domain (FDTD) simulation is used to demonstrate the propagation of the slow mode.

Lag synchronization of bursting neuron systems is explored when the system is subjected to stochastic perturbation. An adaptive feedback control scheme is presented when the parameters of the neuron systems are unknown. At the same time, an adaptive control law is obtained via theoretical derivation so that two slightly mismatched chaotic systems achieved asymptotically lag synchronization. The effectiveness of the proposed scheme is not only confirmed by theoretical analysis, but also verified by numerical simulations.

The high-dimensional chaotic systems (HDCS) have a lot of advantages as more multifarious mechanism, greater the key space, more ruleless for the time series of the system variable than with the low-dimensional chaotic systems (LDCS), etc. Thus, a novel encryption scheme using Lorenz system is suggested. Moreover, we use substitution–diffusion architecture to advance the security of the scheme. The theoretical and experimental results show that the suggested cryptosystem has higher security.

A novel carbon nanotube field-effect transistor with stepwise doping profile channel (SDC-CNTFET) is introduced for short-channel effects (SCEs) improvement. In SDC-CNTFET, the channel is divided into five sections of equal length. Impurity concentration was reduced from 0.8 nm^-1 to zero from the source side to the drain side of the channel, with stepwise profile. The devices have been simulated by the self-consistent solution of two-dimensional (2D) Poisson–Schrödinger equations, within the nonequilibrium Green's function (NEGF) formalism. We demonstrate that the proposed structure for CNTFETs shows considerable improvement in device performance focusing on leakage current and ON–OFF current ratio. In addition, the investigation of SCEs for the proposed structure shows the improved drain-induced barrier lowering (DIBL) and subthreshold swing (SS). Moreover, we will prove that the proposed structure has acceptable performance at different values of channel impurity concentration in terms of delay and power-delay product (PDP). All these investigations introduce SDC-CNTFET as a more reliable device structure in short-channel regime.

The present article proposes a measure of correlation for multiqubit mixed states. The measure is defined recursively, accumulating the correlation of the subspaces, making it simple to calculate without the use of regression. Unlike usual measures, the proposed measure is continuous additive and reflects the dimensionality of the state space, allowing to compare states with different dimensions. Examples show that the measure can signal critical points (CPs) in the analysis of Quantum Phase Transitions (QPTs) in Heisenberg models.

This paper aims to investigate the impact of moisture on mechanical properties of insulation paper. According to the molecular modeling approach proposed by Theodorou, the amorphous cellulose models of insulation paper with different moisture contents were built up to calculate mechanical parameters and hydrogen bond networks. And relevant conclusions could be drawn through further analysis on these calculation results: water molecules can destroy hydrogen bond network between the neighboring cellulose molecules, which might be responsible for the significant decrease of Young's modulus and other mechanical parameters, while no appreciable effect of intramolecular hydrogen bonds on mechanical properties was detected. Thus tensile tests were also carried out to study the moisture influence on the Young's modulus, by which the result of the simulation was approved.

In this paper the design and simulation of an all-optical three-input exclusive-OR (XOR) gate based on semiconductor optical amplifier-Mach–Zehnder interferometer (SOA-MZI) configuration is presented. This gate is constructed of three semiconductor optical amplifiers placed at the arms of the two coupled Mach–Zehnder interferometers. The outputs of these two MZIs are combined at the output port to form the final signal. The proposed scheme does not need a continuous wave (CW) laser for its operation and is designed so that the minimum number SOAs are employed. Theoretical analyses and simulations show that this structure acts as an all-optical three-input XOR logic gate which has many applications in optical data communications.

In the present work, we have studied the second-harmonic generation (SHG) and third-harmonic generation (THG) in a pyramid quantum dot. For this purpose, we first obtain the energy levels and wavefunctions of this system. Then, we have used an analytic expression for the SHG and THG by a compact density matrix approach and an iterative procedure. The SHG and THG enhance and shift to lower energies by increasing the height (h) and vertex angle (φ). According to the results, it is found that the structural parameters have great influence on the SHG and THG of a pyramid quantum dot.