JOURNAL OF RESEARCH ON MANY BODY SYSTEMS
Year:2020 | Volume:9 | Issue:4 (23)|Papers Count:9

Using density functional theory, this study investigated the electronic and optical properties of bilayer h-BN under in-plane biaxial strain. The total energy calculations show that the AB stacking configuration is more stable than AA stacking configuration. Besides, the strain-free bilayer h-BN has an indirect band gap of 4/33 eV along the K  M direction. By applying the compressive strain, the conduction band minimum at the M point moves upward, while the conduction band edge at the  point moves downward. The optical spectra of bilayer h-BN, including the dielectric function and electron energy loss spectrum, move to lower (higher) energies under tensile (compressive) strain.

Sources of renewable energy are a major global concern for researchers. In recent years, the generation of thermoelectric power from waste heat has appeared as a green and clean energy competitor. Beyond the linear response regime, nonlinear thermoelectric phenomena such as negative differential thermoelectric resistance (NDTER) and thermoelectric rectification constitute a new area of research, anticipated to enhance thermoelectric response. Organic thermoelectric materials (TM) have emerged as superior TMs, since they are non-toxic, ecofriendly, and low-cost. Herein, bio-organic materials provide a unique opportunity in developing bio-degradable, flexible and smart TM. In this work, we describe nonlinear phononthermoelectric DNA-based nano devices driven by temperature biases. Remarkably, we found that by applying a temperature difference between the source and the drain, the sensible electric current is generated. The temperature of hot thermostat and the temperature bias are considered as a control parameter. By modulating the temperature bias, NDTER phenomenon can be achieved. NDTER is used to refer to a phenomenon in which the charge current decreases by increasing the temperature bias. Moreover, by fixing the temperature bias between cold and hot reservoirs and varying the temperature of hot reservoir, the charge currents are different for the forward and reverse direction of ∆ T. This is what is called a thermoelectric rectification.

In this study, the modulational instability growth rate of solitary waves due to the interaction of high-intensity laser with relativistic electron-positron plasma is investigated. The relativistic factor and the density of plasma particles are derived analytically as a function of the scalar and vector potentials, plasma temperature, plasma fluid velocity and soliton velocity. Using this factor, the governing equation of vertical component of electromagnetic wave is derived. The dispersion relation of the system is obtained and the variations of the modulational instability growth rate are investigated numerically. It is shown that the modulational instability depends on the wave number and the amplitude of the solitary wave and the unperturbed plasma temperature. Moreover, it is observed that depending on the relative velocity of the plasma fluid and the solitary wave, modulational instability shows opposing behaviors.

In this research, using CORSIKA simulation code with QGSJETII04 and GHEISHA2002d as high and low energy interaction models respectively, proton and iron cosmic ray primaries with 10 17 eV energy and 20-60 o zenith angle are simulated at Tehran observation level (1200m above sea level). By using azimuth angle, arrival time and local coordinates of the muon and electron secondaries as well as rise times of received pulses are calculated. By investigating the rise time as a function of the distance to the Shower Core for different azimuth angle, it is shown that there is an azimuthal asymmetry in the rise time distribution which can be used for mass discrimination of primary cosmic rays.

Graphene is a two-dimensional carbon-arranged structure in the hexagonal lattice, each cell of which is non-Bravais and consists of two A, B substructures of atoms that can be maintained in (from one to several layers maximum of its) two-dimensional properties. Trilayer graphene has been studied due to its stability and abundance over other structures. Considering the type and number of layers and how they are placed in relation to each other in the properties of the material, causing a different dispersion spectrum, we will see different transport properties in the structures. Thus, in the study of trilayer graphene, the three distinct AAA, ABA and ABC– stacked layers were introduced and then analyzed by the Hamiltonian analysis and the Bernal strip structure. Investigations were carried out once in normal conditions and again in the presence of two types of potentials since in the analysis of electrical transport, we consider a piece of trilayer graphene in the presence of a potential sandwiched between two normal these are without potential. The electrical transport properties by analyzing the flow diagram, derived from the Landaure-Buttiker approach, indicate the applicability of trilayer graphene in the production and construction of transistors.

Based on the transfer-matrix method, we theoretically investigate the spin-dependent transport properties in silicene superlattice with extrinsic Rashba spin-orbit interaction (RSOI) in the presence of strain. Due to the RSOI coupling, spin-inversion can be achieved. The spin resolved conductance and spin-inversion effect can be efficiently tuned by RSOI and strain strength. In addition, for particular values of RSOI strength, electrons with perfect spin-inversion transmit through the silicene superlattice. It is found that the spin conductance can be efficiently controlled by the number of barriers. As the number of barriers increases, spin conductivities decrease. The results indicate that for the armchair direction strain, unlike the zigzag direction, the spin polarization can be observed and it increases with increasing the RSOI strength. The magnitude and sign of spin polarization can be adjusted by strain strength. The spin polarization in silicene superlattice for any number of barriers reaches a maximum value at 2% strain.

In this paper, we study the analytical capabilities of photothermal lens spectroscopy technique for detection of trace amounts of contaminants in water. We use an experimental setup with two continuum lasers as pump and probe beams. Different concentrations of iron ions diluted in solvents with relative proportions 4: 1 of water: ethanol is studied. To increase the technique sensitivity, lock-in amplifier and intensity modulation of the pump beam have been used. Additionally, the photothermal signal dependence on modulation frequency is investigated and the best working frequency according to signal enhancement and the lowest standard deviation is found to be 6 Hz. The obtained Limit of detection for doubly ionized iron at the optimum frequency is 20 ng/L.

In this paper, Tetraquark is considered as a bound state of 4-quark systems containing two heavyheavy antiquarks and two light-light quarks ss. Tetraquark is also assumed as a 2-body system consisting of two mesons, each containing a light quark and a heavy quark. Born-Oppenheimer approximation could be employed due to the heavy weight mesons. Hence, the Schrö dinger equation may be solved by replacing the ensuing potential from lattice QCD. Having solved the equations, the binding energy and tetraquark wave function are then obtained in scalar ss channel. Finally, obtained values for binding energy are compared with those reported in the literature, and considering the wave function diagrams for the particle, its tetraquark radius is estimated.

Spin tunneling effect in Single Molecule Magnet Mn12 is studied by instanton calculation technique, using SU(2) spin coherent state in real parameter as a trial function. For this SMM, tunnel splitting (steps in hysteresis loop) arises due to the presence of a Berry phase in action, which causes interference among tunneling trajectories (instantons). In the analytical calculation, the assumption of the linearity of the instanton solution in terms of applied magnetic field is used. It is observed that the number of quenching points of magnetic tunneling and the number of steps in hysteresis loop are equal to the number of points obtained from numerical calculation. Of course, the position of the points (the magnitude of the field in which the tunneling amplitude is zero) is different.