International Journal of Modern Physics B

We study the three-dimensional antiferromagnetic Ising model in both uniform longitudinal $(H)$ and transverse $(\mathrm{\Omega })$ magnetic fields by using the effective-field theory (EFT) with finite cluster $N=1$ spin (EFT-1). We analyzed the behavior of the magnetic susceptibility to investigate the reentrant phenomena that we have seen in the same phase diagram previously obtained in other papers. Our results shows the presence of two divergences in the susceptibility that indicates the existence of a reentrant behavior.

We have studied the effect of applying an external magnetic field on the characteristics of iron oxide (IO) nanoparticles (NPs) synthesized by pulsed laser ablation in dimethylformamide (DMF). The NPs synthesized with and without applying of magnetic field were characterized by Fourier transformation infrared spectroscopy (FT-IR), UV–Vis absorption, scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray diffraction (XRD). SEM results confirmed that the particle size was decreased after applying magnetic field.

The probability distribution of Brownian particles moving in an overdamped complex system follows the generalized Smoluchowski equation, which can be rigorously proven that the exact time-dependent solution for this equation follows Tsallis form. Time-dependent escape rate in overdamped system with power-law distributions is then established based on the flux over population theory. The stationary state escape rate in overdamped system with power-law distribution which has been obtained before based on mean first passage time theory is recovered from time-dependent escape rate as time toward infinity.

Based on the basic principles of stability theory and Lyapunov function, the condition of complete synchronization in coupled Morris–Lecar (ML) neuronal system with chemical synapses is studied in this work. The boundedness of the model solution is proved by analytical approach, the sufficient condition of the complete synchronization is proposed based on the quadratic of the constructed Lyapunov function and the result is verified by simulations.

${\mathrm{\text{Cu}}}_{0.5}{\mathrm{\text{Tl}}}_{0.5}{\mathrm{\text{Ba}}}_2({\mathrm{\text{Ca}}}_{2-y}{\mathrm{\text{Sr}}}_y){\mathrm{\text{Cu}}}_3{\mathrm{\text{O}}}_{10-\delta }(y=0$–$0.4)$ samples have been synthesized at normal pressure at 860${}^{\circ }$C. The main objectives of these experiments to study the role of inter-plane decoupling in suppressing the superconductivity of high temperature superconductors (HTSC). These samples have shown orthorhombic crystal structure and the $c$-axis length increases with increased Sr-doping. All the samples have shown metallic variations of resistivity $(\rho )$ from room temperature down to the onset of superconductivity. The magnitude of the superconductivity is suppressed and the apical oxygen modes are hardened with Sr-doping. These studies have shown that Sr-doping promotes decoupling of conducting ${\mathrm{\text{CuO}}}_2$ planes which suppress the superconducting properties of final compound. The excess conductivity analyses have shown increases in the width of two-dimensional (2D) Lawrence–Doniach (LD) regime with Sr-doping. The coherence length along the $c$-axis ${\xi }_{\mathrm{\text{c}}(0)}$, the inter-layer coupling $J$, the phase relaxation time of the carriers ${\tau }_{\phi }$ and the Fermi velocity $v_F$ of superconductor carriers is suppressed. The underlying reason for the suppression of superconductor properties is the decrease in the density of carriers in the superconductor planes. However, the values of $B_{c0}(T)$, $B_{c1}(T)$ and $J_c(0)$ have been found to increase with the increased Sr-doping, which is suggested to be originating from the enhancement in the flux pinning character which is induced by Sr-doping. The values of magnetic field penetration depth ${\lambda }_{\mathrm{\text{p.d}}}$ and the Ginzburg–Landau (GL) parameter $\kappa$ decrease with Sr-doping and it is also suggested to be originating from the increase of flux pinning character of the samples with Sr-doping.

First-principles calculations are employed to investigate the structural and elastic properties, formation enthalpies and chemical bonding features as well as hardness values of chromium tetraboride $({\mathrm{\text{CrB}}}_4)$ with different structures. The lattice parameters, Poisson’s ratio and $B/G$ ratio are also derived. Our calculations indicate that the orthorhombic structure with Pnnm symmetry is the most energetically stable one for CrB₄. Except for ${\mathrm{\text{WB}}}_{4}P{6}_3/mmc$ structure with imaginary frequencies, another six new structures are investigated through the full phonon dispersion calculations. Their mechanical and thermodynamic stabilities are also studied by calculating the elastic constants and formation enthalpies. Our calculations show that the thermodynamic stabilities of all these ${\mathrm{\text{CrB}}}_4$ phases can be enhanced under high pressure. The large shear moduli, Young’s moduli and hardness values indicate that these ${\mathrm{\text{CrB}}}_4$ phases are potential hard materials. Analyses of the densities of states (DOSs) and electron localization functions (ELFs) provide further understandings of the chemical and physical properties of these ${\mathrm{\text{CrB}}}_4$ phases. It is observed that the large occupations and high strengths of the B–B covalent bonds are important for the stabilities, incompressibility and hardnesses of these ${\mathrm{\text{CrB}}}_4$ phases.

Disorder effects in the thermodynamic properties of an ideal Bose gas confined in a semi-infinite multi-layer structure within a box of thickness $L$ and infinite lateral extent, are analyzed. The layers are first modeled by a periodic array of $M$ Dirac-delta functions of equal intensity. Then, we introduce structural and compositional disorder, as well as a random set of layer vacancies in the system to calculate the internal energy, chemical potential and the specific heat for different configurations. Whereas structural and compositional disorder do not reveal a significant change, a dramatic increase in the maximum of the specific heat is observed when the system is depleted a fraction of the order of 0.1–0.2 of random layers compared to the original, fully periodic array. Furthermore, this maximum, which is reminiscent of a Bose–Einstein condensation for an infinite array, occurs at higher temperatures.

The existence and properties of quantum breathers in a one-dimensional XXZ ferromagnetic Heisenberg spin chain with single-ion easy-plane anisotropy are investigated analytically in the Hartree approximation. We show that the system can support the appearance of quantum breathers, and discuss their existence conditions and properties. In addition, our results show that, for quantum breathers in this system, both the corresponding energy and magnetic moment are quantized.

In previous researches it is demonstrated that reactivity and sensitivity of boron nitride nanotubes (BNNTs) toward gas molecules can be modified by impurity. In this work, oxygen defect for three nitrogen sites was used to study the adsorption of NO molecule through the surface of boroxol ring of oxygen doped BNNT (7,0) with different adsorption patterns, including side-on and end-on. All calculations are performed using the DFT-B3LYP/6-31G${}^{\ast }$ level of theory, and their electronic energies are corrected by gCP and D3 correction terms. High binding energies indicate that NO molecule undergoes chemical adsorption with large charge transfer from the tube which can significantly change electronic properties of the tube. Density of state (DOS) and partial DOS (PDOS) analyses revealed that adsorption of NO molecule on the boroxol ring position is covalent in nature with significant effect on the electronic properties of tube. The Laplacian of electron density, Lagrangian kinetic energy density, Hamiltonian kinetic energy density and potential energy density at bond critical points between the tube and NO indicate that the interaction between the tube and NO molecule is covalent in nature. Topological analysis of the electron localization function shows that electrons in the new formed bonds are approximately localized, meaning that the nature of adsorption process is chemical covalent. The studied nanotube is a suitable candidate to filter and eliminate NO gas molecule.

The stability analysis of a Beddington–DeAngelis (B–D) type predator–prey model driven by symmetric trichotomous noises is presented in this paper. Using the Shapiro–Loginov formula, the first-order and second-order solution moments of the system are obtained. The moment stability conditions of the B–D predator–prey model are given by using Routh–Hurwitz criterion. It is found that the stabilities of the first-order and second-order solution moments depend on the noise intensities and correlation time of noise. The first-order and second-order moments are stable when the correlation time of noise is increased. That is, the trichotomous noise plays a constructive role in stabilizing the solution moment with regard to Gaussian white noise. Finally, some numerical results are performed to support the theoretical analyses.

In this work, we have calculated analytically the energy spectra of electrons and holes in V-grooves quantum wires. To modify wire structure, we have used the equations which suggested in the work of Inoshita et al. We introduce a new effective potential scheme which is applicable and matchable with actual interface geometry of this groove of ridge quantum wires. By applying this effective potential and considering a suitable transformed coordinate that allows the decoupling of the two-dimensional wave functions, we have calculated eigen values of the charge carriers in three states as well as the wave functions. We found that by increasing the curvature at the top of quantum wire $(b)$ the energy eigen value decreases. Our results are in good agreement with the earlier investigations.