International Journal of Modern Physics B

In the present paper, we have investigated SmAlO₃ for their thermodynamic properties under effect of pressure and temperature by employing density functional theory (DFT) and quasi-harmonic Debye model. The various thermodynamic properties like Bulk Modulus, entropy, internal energy, Helmholtz free energy, Debye temperature, coefficient of thermal expansion, Grüneisen parameter and heat capacities of the ternary alloy are calculated. We found that Bulk Modulus, Debye temperature and Helmholtz free energy have decreasing trend with rise of temperature while their values have increasing behavior with rise of pressure. The internal energy of the system almost remains same with variation in pressure but temperature effectively increasing it. Our results are in good agreement with available data at low-temperature limit.

The structural, electronic, elastic and mechanical properties of ZrNiPb half-Heusler alloy under pressure ranging from 0 to 25 GPa have been studied using the density functional theory within the generalized gradient approximation (GGA). The results of ambient condition were in good agreement with the available theoretical and experimental data. Our electronic structure and density of state results show that ZrNiPb is an indirect bandgap semiconductor half-Heusler alloy with a narrow energy gap of 0.375 eV. Based on the calculated elastic constants (C${}_{11}$, C${}_{12}$ and C${}_{44}$), Young’s modulus (E), Poisson’s ratio ($\nu$), Shear modulus (G), Zener anisotropy factor (A) and brittle-ductile behaviors under pressure have been discussed. The calculated Poisson’s ratio shows that ZrNiPb undergoes a relatively small volume change during uniaxial deformation. We show that the chemical bonds in ZrNiPb are stronger due to the high value of C${}_{11}$.

We present ultrasonic measurements on the rare earth tritelluride HoTe₃ compound. Different anomalies are observed at the upper and lower charge density wave phase transition T${}_{\mathrm{\text{CDW1}}}$ = 284 K and T${}_{\mathrm{\text{CDW2}}}$ = 120 K. A striking T² temperature dependence of the velocities of the longitudinal C${}_{11}$, C${}_{33}$ and shear C${}_{55}$ modes is observed in the ordered phase below the lower CDW phase transition T${}_{\mathrm{\text{CDW2}}}$. Such a behavior is related to the temperature dependence of the CDW order parameter.

A quantum model for the interaction between asymmetric two two-level atoms and an electromagnetic field is presented. The $k$-photon processes and atom–atom interaction are considered in this quantum model. The wavefunction for asymmetric case of the proposed model is obtained analytically. While, the explicit analytical formula of the wavefunction for symmetric case was calculated in previous works. Initially, the electromagnetic field is in the coherent state and two two-level atoms are identical in the excited states. For the proposed model, some statistical aspects are obtained, such as the linear entropy, atomic population inversion, entropy squeezing, atomic variance and von Neumann entropy. The evaluations of these statistical properties are discussed for the variation in the detuning parameters. Moreover, the nonclassical effects for atom–atom interaction are observed.

In this paper, we study a new type of immunization strategy which is applied to weighted networks. It helps us in maintaining the necessary network efficiency by limiting the transmission (lowering the weight of edges) while suppressing the spread of the epidemic. It is similar to the inflammation around the infected parts of our body, which can not only prevent the disease spreading but also protect the function of the body. First, we set the rate of transmission to be proportional to the edge weight based on the S-I epidemic spreading model. Then, we show the detailed dynamic evolution of the infected nodes which facilitates an effective epidemic control. Theoretical analysis and simulation results indicate that the new immunization strategy can be used to prevent the epidemic spreading effectively, while maintaining the high efficiency of the network.

Real Space Renormalization Group (RSRG) treatment of Ising model for square and simple cubic lattice is investigated and critical coupling strengths of these lattices are obtained. The mathematical complications, which appear inevitable in the decimated partition function due to Block-spin transformation, is treated with a relevant approximation. The approximation is based on the approximate equivalence of $ln(1+f(K,\{{\sigma }_{n\cdot n}\}))\simeq f(K,\{{\sigma }_{n\cdot n}\})$ for small $f(K,\{{\sigma }_{n\cdot n}\})$, where K is the nearest neighbor coupling strength and $\{{\sigma }_{n\cdot n}\}$ is the nearest neighbor spins degrees of freedom around a central spin. The values of the critical coupling strengths are obtained as 0.4830 for square lattice and 0.2225 for simple cubic (SC) lattice. The corresponding critical exponents values $\alpha$ and $\nu$ are also calculated within very acceptable agreement with those values obtained from numerical works.

A tunable transverse electric (TE) and transverse magnetic (TM) wave splitter using one-dimensional plasma dielectric photonic crystal which consists of plasma arranged periodically in a host dielectric medium is proposed. We performed a detailed study to explore the phenomena of reflection and transmission that occurs on obliquely incident electromagnetic wave propagating in the proposed plasma dielectric photonic crystal. We exactly calculated the transmittance based on the transfer matrix method. We find that if the parameters are selected appropriately, in the TE-stop or TM-stop frequency region, the other polarized component TM or TE wave is totally transmitted. The results also show that the dielectric constant, plasma thickness, incident angle and the applied magnetic field have significantly changed the properties of the TE/TM wave splitter. Moreover, the external magnetic field can be used as a kind of tunable method once the splitter is fabricated. Parameter dependence of the effects for the TE/TM wave splitter is calculated and discussed.

We investigate a Bose–Einstein condensate held in a 1D tilted bichromatical optical lattice potential by constructing its Poincaré sections in phase space. We explore dynamic of the system based on the relations between the system parameters and the solution behaviors. It is demonstrated that the system exhibits shock-wave like dynamic. The power spectrum graphs, bifurcation and Lyapunov exponents of BEC system are also presented.

The phase diagrams and the magnetizations in a graphene-like two-dimensional nanoparticle described by the transverse Ising model are investigated by the use of the effective-field theory with correlations. We have found some characteristic behaviors especially for the system with a small transverse field and a small surface exchange interaction, such as the reentrant phenomena.

We investigate the dispersion relation and decay rate of plasmon modes in a double-layer system made of bilayer graphene (BLG) and infinite GaAs quantum well at zero-temperature within the generalized random-phase-approximation and taking into account the 2DEG layer-thickness and inhomogeneity of the background dielectric. We illustrate that the acoustic plasmon dispersion curve of the considered system differs significantly from that of monolayer graphene (MLG)–GaAs heterostructure and BLG–GaAs without layer-thickness. Calculations also demonstrate that meanwhile the optical plasmon curve is affected slightly by spacer width and exchange-correlation, the acoustic one depends remarkably on the interlayer distance, inhomogeneity of the background dielectric, carrier densities, spacer dielectric constant, quantum well width and exchange-correlations.

In the correlated electron system with the pseudogap, full-gapped domains and Fermi-arced domains coexist. These domains are created by the quantum-fluctuated antiferromagnetic correlation that generates the short-ranged attractive potential to produce the Fermi arcs and the superconductivity. In the full-gapped domains, s-wave or $(d_{x^2-y^2}\pm i{d}_{xy})$-wave symmetry of the electron pairs is favored. In the Fermi-arced domains, only $d_{x^2-y^2}$-wave symmetry of pairs is stable. Superconductivity of different pairing symmetry coexists in different domains as well. Different from the Cooper pairs, the correlated electrons pair up in the real space with an energy gap. Gapless states, on the contrary, hinder the development of superconductivity.

By introducing multiple-site correlation functions, we propose a hierarchical Green’s function approach, and apply it to study the characteristic properties of a two-dimensional (2D) square lattice Hubbard model by solving the equation of motions of a one-particle Green’s function and related multiple-site correlation functions. Under a cut-off approximation and taking the Fourier representation of multiple-site correlation functions, we obtain an analytical expression of one-particle Green’s function with static correlation functions. Then we calculate the spectral density function of electrons, and obtain that besides two main peaks corresponding to the lower and upper Hubbard bands in the spectral density function, there emerge some novel states between these two main peaks, and the total spectral weight of these emerged states is proportional to the hole doping concentration $\delta$. Meanwhile, there also emerge some collective modes related to possible charge/spin density wave and/or electronic pairing density wave ordering states. This calculation is completely consistent with the spectroscopy observations of the cuprate superconductors in normal states. On the other hand, the appearance of the static correlation functions in the one-particle Green’s function can be used to describe the intertwined orders observed in the normal state of the cuprate superconductors.

To investigate the configurations and the electrical performance of the Pb–I films, the geometries and electronic properties of the Pb${}_n$I and Pb${}_n$I₂ (n = 1–6) clusters are calculated by density functional theory at the GGA/PBE functional. The results reveal that I atoms prefer to occupy the symmetrical positions which are far from the centers of the Pb${}_n$ clusters. The Pb₂I₂ clusters are more structurally stable than the neighbors by the average binding energy. The PbI, Pb₃I, PbI₂, Pb₄I₂ and Pb₆I₂ clusters are more dynamically stable than their neighbors by the HOMO–LUMO gaps. The adsorption capacity of an I atom on the Pb₂ cluster is the strongest compared to those of the other Pb${}_n$ (n = 1–6) clusters. NBO analysis reveals that the 5p orbital of I atoms in the Pb–I clusters acquires more electrons than the 5s orbital loses.

With the help of the transfer-matrix method, we theoretically investigate the effect of the $\delta$-doping on the magnetoresistance (MR) effect in a magnetic nanostructure, which can be realized by depositing two ferromagnetic strips on the top and bottom of a nanostructure and using the atomic layer doping technique. It is shown that an obvious MR effect can be obtained in this device, and it can be tuned by the position and weight of the $\delta$-doping. This device can be used as a $\delta$-doping-dependent MR device for magneto electronics applications.