International Journal of Modern Physics B

First experiments on the growth of oxypnictide F-doped LaFeAsO thin films indicated an incomplete normal-to-superconducting transition and offered a work programme challenging to overcome possible difficulties in their fabrication. In this regard the possibility of an all in-situ epitaxial growth appeared to be a matter of time and growth parameters. The following review clarifies that F-doped oxypnictide thin films are extremely difficult to grow by in-situ PLD due to the formation of very stable impurity phases such as oxyfluorides (LaOF) and oxides (La₂O₃) and the loss of stoichiometry possibly due to incongruent evaporation of the target or re-evaporation of volatile elements at the substrate surface. However, the review also demonstrates that the employed two-step fabrication process for oxypnictide thin films has been successfully applied in the preparation of clean polycrystalline as well as of epitaxial thin films. Fundamental investigations on the upper critical field, its temperature dependence and its anisotropy contributed to an understanding of multiband superconductivity in oxypnictides.

A new class B_k(α, ρ, γ) of analytic functions defined in the unit disc is introduced. This class contains generalized Bazilevic functions of type α. Arclength problem, coefficient and distortion results are studied and also discussed the rate of growth of Hankel determinant for these functions.

Time-reversal had always been assumed to be a symmetry of physics at the fundamental level. In this paper we will explore the violations of time-reversal symmetry at the fundamental level and the consequence on thermodynamic systems. First, we will argue from current physics that the universe dynamics is not time-reversal invariant. Second, we will argue that any thermodynamic system cannot be isolated completely from the universe. We then discuss how these two make the dynamics of thermodynamics systems very weakly irreversible at the classical and quantum level. Since time-reversal is no longer a symmetry of realistic systems, the problem of how macroscopic irreversibility arises from microscopic reversibility becomes irrelevant because there is no longer microscopic reversibility. At the classical level of a thermodynamic system, we show that the H theorem of Boltzmann is still valid even without microscopic reversibility. We do this by deriving a modified H theorem, which still shows entropy monotonically increasing. At the quantum level, we explicitly show the effect of CP violation, small irreversible changes on the internal states of the nuclear and atomic energy levels of thermodynamic systems. Thus, we remove Loschmidt's objection to Boltzmann's ideas.

Dynamics of a pinned dislocation kink controlled by the acting DC and AC forces is studied analytically. The motion of the kink, described by sine-Gordon (sG) equation, is explored within the framework of McLaughlin–Scott perturbation theory. Assuming weakness of the acting AC force, the equation of motion of the dislocation kink in the pinning potential is linearized. Based on the equations derived, we study stochastic behavior of the kink, and determine the probability of its depinning. The dependencies of the depinning probability on DC and AC forces are analyzed in detail.

First-principles calculations have been conducted to study the electronic structures and optical properties of 2Al- and 2Ca-doped β-Si₃N₄. Calculated formation energies of 2Al- and 2Ca-doped systems are 5.9745 eV and 18.9376 eV, respectively, indicating the former has a stable structure than the latter. The band gaps of two systems are 3.1573 eV and 2.0155 eV, respectively, reveals that the band structures of them behave like semiconductors. The static dielectric constants of two systems are 40 and 37, respectively, which denotes their potential applications in electronics and optics. The strong absorption bands ranging from 4 eV to 16 eV become much sharper and show a red-shift after doping. The offset of 2Al-doped system is larger than that of 2Ca-doped system. The absorption coefficient can be remarkably modulated by doping. In calculated frequency-dependent electron energy loss spectra (EELS) of doping systems, the host peaks all locate at about 15 eV.

In this report, the synthesis of zinc ferrite (ZnFe₂O₄) by co-precipitation method has been presented along with its subsequent characterization by using X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and electron spin resonance (ESR) techniques. The obtained XRD results of as-synthesized sample indicates the cubic spinel phase formation, which was confirmed from the XRD data of the above calcined sample at 1000°C. By using VSM, a complex magnetic structure was observed with substantial change on calcined sample. The ESR result of zinc ferrite sample studied at room temperature was found to be significantly different from that of the low temperature results, especially after heat-treatment.

In this paper, we studied a generalized Bose–Hubbard model on a checkerboard lattice with topologically nontrivial flat-band. We used mean-field method to decouple the model Hamiltonian and obtained phase diagram by Landau theory of second-order phase transition. We further calculate the energy gap and the dispersion of quasi-particle or quasi-hole in Mott insulator phase and found that in strong interaction limit the quasi-particles or the quasi-holes also have flat-bands.

We explore the charge transfer in the telomere G-Quadruplex (TG4) DNA theoretically by the nonequilibrium Green's function method, and reveal the topological effect of the charge transport in TG4 DNA. The consecutive TG4 (CTG4) is semiconducting with 0.2 ~ 0.3 eV energy gap. Charges transfer favorably in the CTG4, but are trapped in the nonconsecutive TG4 (NCTG4). The global conductance is inversely proportional to the local conductance for NCTG4. The topological structure transition from NCTG4 to CTG4 induces abruptly ~ 3nA charge current, which provide a microscopic clue to understand the telomerase activated or inhibited by TG4. Our findings reveal the fundamental property of charge transfer in TG4 and its relationship with the topological structure of TG4.

The doping effects of low melting-point nonmagnetic Sb³⁺ ions on the microstructure and electromagnetic properties of Mn–Zn ferrites were studied. All the samples were prepared by traditional ceramic technique. According to the investigation on the microstructure, it was found that all the samples consisted of ferrite phases with typical spinel cubic structure, and with increasing doping content of Sb³⁺ ions, the lattice constant of the ferrites decreased but the grain size increased; the elemental analysis taken on the ferrite grain and grain boundary indicated that a portion of Sb³⁺ ions entered into the ferrite lattice. Through the measurement of magnetic properties, it was revealed that, the saturation magnetization and initial permeability of the samples rose with small doping content of Sb³⁺ ions but decreased with additional Sb³⁺ doping; the Curie temperature decreased monotonously with Sb³⁺ doping; and the coercivity rose with increasing doping content of Sb³⁺ ions. The analysis of dielectric properties indicated that the dielectric constant of the doped Mn–Zn ferrites increased with increasing doping content of Sb³⁺ ions.