Modern Physics Letters B

Using density functional theory, we investigated the stability, magnetism and band structures of hexagonal boron nitride (h-BN) monolayer with graphene domains (h-BNC heterostructure). The number of the carbon atoms in the graphene domain is fixed with shapes and locations in the h-BN monolayer different. We found that these h-BNC heterostructures exhibit different stability, magnetism and energy band gap. Our results show that the stability of the system is related to the number of C–C/C–N/C–B bonds and unpaired sublattices in the graphene domains. Some h-BNC heterostructures are magnetic with the magnetic moment equal to the difference of the nonequivalent sublattices in graphene domains, which obeys Lieb's theorem. Because of the spin splitting of the mid-gap states, the band gaps of the magnetic heterostructures are smaller than that of the nonmagnetic ones.

We find that in optical fields' diffusion process, the l-photocounting probability formula at time t = 0 should be generalized to a new formula at time t, where ρ(0) is the initial density operator of the field, L_l is the Laguerre polynomial, : : denotes normal ordering, and ξ is the quantum efficiency of the photocounting detector. This new formula brings much convenience for different ρ₀, because for deriving there is no need to derive the corresponding ρ(t) in the diffusion channel.

The relationship between quantum entanglement and non-locality is studied in a two-qubit system for pure states and Werner states. It is found that Werner states are more entangled than pure states if one compares the negativity for a given degree of non-locality. Furthermore, we also find that the entanglement produces sudden death for pure states but reaches to a fixed value for Werner states if the non-locality is not satisfied.

A new technique for designing the crystal shape and orientation of single crystalline hematite (α-Fe₂O₃) nanoparticles was developed. By thermal decomposition of FeCO₃ single crystals, a novel micro-scale core–shell structured α-Fe₂O₃/Fe₃O₄ crystals were obtained. The shape of the crystal remained unchanged when single crystals of FeCO₃ phase changed into α-Fe₂O₃ at 450°C. The rhombohedral α-Fe₂O₃ unit cell had the same orientation with the parent rhombohedral FeCO₃. The α-Fe₂O₃ single crystal nanoparticles were formed continuous and intricate network in the core of Fe₃O₄ thin shell, and its temperature dependence of cell dimensions show non-linearity.

In this paper, a statistical theory of N-soliton systems with antisymmetric wave functions is presented. As such, the wave functions of the soliton waves have equal but opposite amplitudes. In the wave function representation, the governing energy and continuity conditions are found to be linear, admitting a linear superposition of the soliton waves functions. This property is used to form the combined wave function for the system hence to calculate its total (macroscopic) energy. The statistical theory is applied to model phase transitions in ferromagnetic materials, and used for the case of common ferromagnetic substances, such as iron (²⁶Fe), cobalt (²⁷Co) and nickel (²⁸Ni). The estimated first phase transitions are found to correspond to the respective Curie temperatures of these substances. Based on the energy calculations, the general hysteresis behavior of ferromagnetic materials is derived as a consequence of the model. The statistical theory is useful in the study of ferromagnetic phase transitions, for estimating the Curie point temperature, and an exact determination of the heat capacity of magnetic materials.

To minimize the critical dimension of resistive switching random access memory (RRAM), good anisotropy and selectivity with diblock copolymer are required for silicon dioxide etching. Inductively coupled plasma (ICP) etcher using CHF₃/H₂ mixture is used for effective etching of SiO₂. In this paper, a commercial software CFD-ACE+ was used to simulate reactor scale and feature scale model of SiO₂, diblock copolymer and Pt. Etch properties of SiO₂ at different chamber conditions were discussed. It was found that etch rate increased at the expense of selectivity as ICP power increased, which was the opposite trend for pressure. Selectivity and anisotropy are achieved at neutral to ion flux ratio 100:1. Moreover, the appropriate overetch time for SiO₂ layer to Pt layer was discussed.

We study the Cooper pairs configuration, the magnetic induction and the magnetization in a superconducting nanoscopic square with a central square tower embedder in a uniform applied magnetic field. We study the vortex configurations for a superconductor in two scenarios; in the vicinity of the Bogomolny point and with . We also considered the Neumann and Dirichlet boundary conditions via deGennes length penetration. We show that the critical fields depends both on the boundary conditions and Ginzburg–Landau parameter.

The characteristics of the plasma with difference between the electron temperature and gas temperature were investigated and the relationship between the plasma ionization degree and the internal energy of a system was obtained. A group of equations included the chemical reaction equilibrium equation, the chemical reaction rate equation and the energy conservation equation were adopted to calculate the electron density, the electron temperature and the atom temperature with a given internal energy. These equations combined with Navier–Stokes (N–S) equations is solved by a smooth particle hydrodynamic (SPH) code. The charges generated in hypervelocity impacts with five different velocities are calculated and verified with the empirical formulas. The influence of a critical velocity for plasma generation is considered in the empirical formula and the parameters are fitted by the numerical results. By comparing with the results in reference, the fitted new empirical formula is verified to be reasonable and useful for a wide range of impact velocity.