International Journal of Modern Physics B

Hall viscosity is a dissipationless transport coefficient whose value is quantized in units of the density in some topological phases and may be used as a measure of topological order. I give an overview of the Hall viscosity, its relation to Hall conductivity in Galilean invariant theories and its realization in effective theories.

The microstructure and nonohmic properties of SnO₂–Ta₂O₅–TiO₂-CuO varistor system were investigated. The proposed samples were doped with different contents of CuO (0–6 mol%) and sintered at 1400°C for 2 h with conventional ceramic processing method. In all the samples, the commonly identified phase was SnO₂ (rutile); however, with increasing doping amount of CuO, the peaks of CuO phase emerged in the X-ray diffraction (XRD) patterns. Scanning electron microscopy (SEM) examination on the fractured surfaces of the samples revealed that a minor amount of CuO dopant can facilitate the sintering of the varistor ceramics, but excessive CuO would mainly segregate at grain-boundaries. The doped CuO may also act as a modifier in the SnO₂ based varistors. The measured electric-field versus current-density characteristics of the samples indicated that both nonlinear exponent and varistor voltage increased with increasing doping amount of CuO up to 3 mol% and then decreased with excessive CuO.

Inspired from the connection between Lie symmetries and two-dimensional materials, we propose a new statistical lattice model based on a double hexagonal structure appearing in the G₂ symmetry. We first construct an Ising-1/2 model, with spin values σ = ±1, exhibiting such a symmetry. The corresponding ground state shows the ferromagnetic, the antiferromagnetic, the partial ferrimagnetic and the topological ferrimagnetic phases depending on the exchange couplings. Then, we examine the phase diagrams and the magnetization using the mean field approximation (MFA). Among others, it has been suggested that the present model could be localized between systems involving the triangular and the single hexagonal lattice geometries.

The thermal properties of TiN-based nitrides are studied using first-principles calculations. Bulk modulus, thermal expansion, heat capacity, vibrational entropy and melting point for TiN–X compounds are computed, considering all possible transition-metal solute species X. The calculated properties show clear trends as a function of d-band filling. The results indicate that the largest increase of melting point of TiN is caused by alloying element W. Computed thermal properties for pure TiN are in good agreement with the available experimental and theoretical data.

Shallow traps play a significant role in influencing charge dynamics through organic molecular thin films, such as pentacene. Sandwich cells of pentacene capped by gold electrodes are an excellent specimen to study the nature of underlying charge dynamics. In this paper, self-consistent numerical simulation of I–V characteristics is performed at various temperatures. The results have revealed negative value of Poole Frenkel coefficient. The location of trap energy level is found to be located at 0.24 eV above the highest occupied molecular orbit (HOMO) level of pentacene. Other physical parameters related to trap levels, such as density of states due to traps and effective carrier density due to traps, have also been estimated in this study.

The dynamics of quantum state transfer through a thermal spin chain with Heisenberg interaction is discussed by numerically calculating the maximal fidelity in a finite transfer time for the chains with several numbers of sites. We find that the maximal fidelity does not decrease monotonously with the increase in the temperature, but depends on the maximal allowed transfer time. Finally, we compare the results of thermal channel with the transfer through ground state channel.

Ba₄LaTi_0.3Sn_0.7O₁₅ ceramic was prepared through conventional solid state mix oxide route followed by characterization using X-ray diffraction (XRD) and scanning electron microscope (SEM) for phase and microstructural investigation. The dielectric properties at low and microwave frequencies were measured using LCR meter and vector network analyzer. XRD results revealed single phase ceramics and the microstructure was comprised of compact grains with size ranging from 4–12 μm. The lattice parameters refined by the least squares method were a = b = 5.7680(2) Å, c = 11.7491(6) Å, V = 337.81 ų and Z = 1. Optimum properties i.e., ε_r~44.6, Q_uf_o~15, 500 GHz and τ_f~2.05 ppm/°C were achieved for Ba₄LaTi_0.3Sn_0.7 Nb₃O₁₅ ceramic sintered at 1475°C for 4 h.

The bending vibration band structure of phononic crystal (PC) beam is solved by a unified formulation of the modified transfer matrix (MTM) method in this paper. The improvement of MTM method is the introduction of constitutive matrix U and matrix of derivative functions V, which standardizes and simplifies the deduction by the matrix operation. The band structure of an epoxy-aluminum PC Timoshenko beam is calculated by both MTM method and plane wave expansion (PWE) method. The results show that the present MTM method has a great advantage in the precision of the result. In addition, the formulation of transfer matrix derived from Timoshenko beam condition is a general form which is also suitable for other general beam structures just by replacing corresponding matrices.

Collective behavior in animal groups such as schools of fish, swarms of insects or flocks of birds, although a phenomenon widely studied in biological systems, is subject of great interdisciplinary interest. An important tool to describe the dynamics of collective motion and ordered live organisms is the concept of self-propelled particles. Proposed by Vicsek and collaborators, it was considered in this model only as an (single) interaction rule, set as alignment, where particles align to motion the nearest neighbors. In this paper, we have considered a variant of this model by adding a second rule called repulsion zone, where particles repel each other at short distances, in order to investigate the influence of this zone on directional order of the particles.