Modern Physics Letters B

In this paper, general description of a cellular structure formation in a system of interacting particles has been proposed. Analytical results are presented for such structures in colloids, systems of particles immersed into a liquid crystal and gravitational systems. It is shown that physical nature of formation of cellular structures in all systems of interacting particles is identical. In all cases, a characteristic of the cellular structure, depending on strength of the interaction, concentration of particles and temperature, can be obtained.

Complex networks are widely used to model the structure of many complex systems in nature and society. Recently, fractal and self-similarity of complex networks have attracted much attention. It is observed that hub repulsion is the key principle that leads to the fractal structure of networks. Based on the principle of hub repulsion, the metric in complex networks is redefined and a new method to calculate the fractal dimension of complex networks is proposed in this paper. Some real complex networks are investigated and the results are illustrated to show the self-similarity of complex networks.

In this paper, we have provided a systematic measurement of the longitudinal resistance R_xx of quantum Hall transition in a two-subband two-dimensional electron system. The data shows that the standard scaling behavior with single critical point remains unchanged even with strong Landau level degeneracy. There is no definite evidence to support the recent prediction that the width of transition region becomes finite when extrapolated to zero temperature, resulting from Landau level mixing.

In this paper, we report strong variations in the Raman spectra of different carbon allotropes samples, for temperatures ranging from 83 K to 1123 K. The temperature dependence of D and G peak frequencies in the Raman spectrum of diamond, graphite, graphene, and carbon nanoparticles (CNPs) with 20 nm dot-size were investigated. These effects caused by temperature can be estimated from the changes in position and in linewidth of peak full width at half maximum (FWHM) G in the Raman spectrum of each sample. The broadening for each allotrope under the same conditions of temperature were: diamond ~ 4 cm^-1, graphite ~ 50 cm^-1, graphene ~ 5 cm^-1 and nanoparticles ~ 7 cm^-1. We also used scanning electron microscopy (SEM) to study the morphology and determine the size of the samples. According to the experimental data, the residual structural disorder and stress present in the samples are enhanced with temperature and responds for the observed changes in the Raman spectra. We present a systematic study of the temperature-dependent Raman spectra of four carbon allotropes.

In this paper, the electronic structures and magnetic properties of the Cu-doped ZnO monolayer are investigated by means of first-principles methods based on density functional theory. Numerical results show that the Cu dopant can induce the half-metallic ferromagnets in the ZnO monolayer due to the strong p–d coupling. In addition, the semiconductor band gap is also decreased when Zn atom is substituted by Cu atom in the ZnO monolayer. Moreover, the formation energy calculations also indicate that it is energy favorable and relatively easier to incorporate Cu atom into the ZnO monolayer under Zn-rich experimental conditions.

In this paper, using first-principles calculations the electronic and magnetic structure of trans- and cis-polyacetylene based magnetic tunnel junctions is investigated. Energy minimization calculations are performed to obtain the equilibrium bonding length at the metal/polymer interfaces. Magnetic proximity-induced spin polarization across the polymeric chains is calculated and it is shown that irrespective of the parallel or anti-parallel magnetic configuration of the electrodes the carbon atoms attaching the Fe electrodes get oppositely polarized. Local density of states calculations reveal that, as a result of being attached to the ferromagnetic leads, states are induced in the energy gap region of molecule's p_x and p_y orbitals which infers their contribution in electronic transmission of the device.

In this paper, a proposal for how to store and retrieve the quantum state of a nonstationary photon wave packet in quantum dots is presented. Here, the input photon with two central frequencies is different from the usual photon. In order to store the quantum state of the input photon more stably, we control the magnetic field to transfer the coherence from electronic spins to nuclear spins. In this paper, we also suggest one method to produce a photon with two central frequencies, and point out a possible way to code quantum information.

The glasses of compositions xFe₂O₃⋅ (40 - x)Bi₂O₃⋅60B₂O₃⋅2V₂O₅ have been prepared by the standard melt-quenching technique. Amorphous nature of these samples is ascertained by XRD patterns. The presence of BO₃ and BO₄ units is identified by IR spectra of glass samples. The absorption edge (λ_cut-off) shifts toward longer wavelengths with an increase in Fe₂O₃ content in the glass matrix. The values of optical band gap energy for indirect allowed and forbidden transitions have been determined and it is found to decrease with increase in transition metal ions. The Urbach's energy is used to characterize the degree of disorder in amorphous solids.