نشریه پژوهش سیستم های بس ذره ای
سال هشتم شماره 4 (پیاپی 19، زمستان 1397)

In this study, we have obtained a parametric relationship for the entanglement measurement between each pair of qubits for graphs with more than four qubits. We have also calculated the value of entanglement in five-qubit entangled graphs. Analysis of our results shows that the total of 1024 five-qubit entangled graphs based on the maximum entanglement between each pair of qubits, categorizes into 31 groups and if we consider the number of graph edges and degrees of vertices then these states are classified in 40 classes. Also based on the numerical results obtained from multipartite entanglement measures such as generalized concurrence, global measurements, and Meyer-Wallach measurements, we show that 1024 graphs of the five-qubit system are in 24, 32 and 23 categories, respectively. As well as we conclude that the maximum amount of entanglement belongs to the cycle graph and the minimum value belongs to the one-edge graph. While the maximum amount of entanglement between each pair of qubits is in the one-edge graph and the minimum value is in the complete graph.

In this study the effect of different polymers (PVA, PVP, PEG and EG) on the structural and magnetic properties of the cobalt ferrite with general formulae CoFe2O4 have been investigated. The structural, morphological and magnetic properties of the samples have been studied by X- ray diffraction (XRD), Fourier transform infrared (FT-IR), Field emission scanning electron microscopy (FE- SEM) and Vibrating sample magnetometer (VSM). X-ray diffraction measurements along with Rietveld refinement confirmed the crystalline structure for all the ferrites prepared. The magnetic properties of samples indicated that maximum (71 emu/g) and minimum (50emu/g) amount of saturation magnetization was achieved for samples prepared using PEG and PVP, respectively. Moreover, maximum (1200 Oe) and minimum (904 Oe) amount of coercivity was achieved for samples prepared using PVA and PEG, Respectively. Our results indicate that it is possible to tune magnetic properties of ferrites by using different polymers during the preparation process.

Silicon carbide (SiC) is an attractive ceramic for most industries due to its unique mechanical, physical, thermodynamical and chemical properties. In this research, the mechanical, and thermodynamical properties of 3C silicon carbide were estimated by molecular dynamics and density functional theory in high temperature and pressure. The results were compared and validated by valid theoretical and experimental results. The molecular dynamics calculations were carried out by Tersoff, and Vashishta interatomic potentials. The results indicated that both potentials the have high capability in optimizing SiC structure. The estimated mechanical properties of 3C silicon carbide including elastics constants, Bulk, Young, and Shear moduli and Poisson ratio in high temperature and pressure (50 GPa and 1000 K, respectively) which were calculated by Tersoff potential were in good agreement with experimental results. The thermodynamic properties including melting point, Debye temperature, specific heat capacities at constant volume and pressure, linear thermal expansion coefficient, and thermal conductivity in ambient and high pressure were calculated by molecular dynamic and functional theory.

The effect of size scintillator on the shape of the response function for cylindrical NE213 and NE102 organic scintillation detectors have been studied. The response function of scintillators with different size when exposed to 137Cs, 60Co and 22Na gamma sources have been simulated using MCNPX-PHOTRACK hybrid code and then measured. Using the simulated and experimental response functions, the influence of the size of scintillator on the shape of the response function, efficiency, energy resolution and energy resolution function of NE102 and NE213 detectors have been calculated. The comparison confirms that the simulated efficiencies and energy resolutions of scintillators represents a promising agreement with experimental data and previously published experiments.

The adsorption of h-BN monolayer on WS2 nano sheet was studied in the framework of density functional theory using Quantum ESPRESSO package. First-principle calculations with different exchange-correlation functionals including LDA, GGA, semi-empirical and ab-initio van der Waals in the forms of DFT-D2, vdW-DF2B86R and vdW-DF2 have been performed to evaluate the performance of different functionals in describing bonding mechanism, adsorption energy and interlayer distance of WS2 monolayer on h-BN layer. In order to include the van der Waals (vdW) interactions in our calculations, we used the DFT-D2 and vdW methods and found the vdW-DF2B86R seems to be the most qualified approach. Both vdW and semi-empirical methods predict a physical adsorption with no net charge transfer between the WS2 layer and the corresponding substrates. In addition, we investigated the electronic and structural properties and density of states of WS2 and h-BN heterolayers by vdW-DF2B86R functional. Based on our calculations, WS2/h-BN heterostructure show a direct band gap at the K-point, which has been experimentally observed.

In this paper, by applying strain and magnetic barrier simultaneously in gapped graphene which has been located between two ferromagnetic electrodes, the transmission of the coefficient and conductance of the junction have been studied and the condition has been provided to reach giant magnetoresistance. The results show that the valley gap cannot be achieved in graphene only by using strain and it comes into being in strain graphene with magnetic barrier and it is controllable by changing substrate mass gap. Also, it is found that the MR strongly depends on the strain, magnetic barrier, magnetization configuration of the ferromagnetic regions, and substrate mass gap in a way that by applying appropriate values for these parameters, the MR can reach up to 100%. Specially, for K valley, by changing the configuration magnetization from parallel to antiparallel, the antiparallel conductance reduces to zero faster than the parallel conductance for the above parameters. So, the junction is transparent only for parallel conductance leading to an increase of MR to 100%. Tunability of the MR reveals the potential application of the proposed junction for future spin-electronics devices.

There are several methods to synchronize chaotic systems. In this work, we have proposed the adaptive synchronization to study the three interesting systems. These systems are Rössler-Rössler, Liu-Liu, and Liu-Rössler. We have simulated the synchronization of the systems under different circumstances. A numerical simulation of synchronization between the proposed systems demonstrates that the systems can synchronize with this method perfectly even in the presence of unknown parameters. We have deduced that the synchronization speed in the first system (Rössler-Rössler) is faster than the rest. Also, the second system (Liu-Liu) is synchronized faster than the third system. According to the results obtained in this paper, we can say that the adaptive synchronization works better on similar systems such as Rössler-Rössler and Liu-Liu.

Based on the theory of periodically driven quantum systems, a new pathway can be created to find topological phases by applying light on solid state systems. Here, we theoretically apply a linear laser beam to a one-dimensional lattice as a quantum wire. Using Floquet theory we study the quasi-energy of the system in a geometry with either finite or periodic boundary conditions. Topologically, the system has distinct phases depending on the laser intensity significantly. The results show that for different values of hopping dimerization and laser intensity the system hosts zero, one, two or three pairs of edge states. Furthermore, we evaluate appropriate topological invariants that for one, two, and three pairs of edge states take the values of 1, 2, and 3, respectively. Also, symmetry arguments show that there are time-reversal, particle-hole, chiral and parity symmetries. We also find that by breaking the parity symmetry, the edge states disappear resulting in this symmetry plays a key role.

In this research, we study quark confinement by dyons as the vacuum structures of QCD theory and apply the particle mesh Ewald’s (PME) method – the generalization of Ewald’s method - on non interacting and interacting ensembles of dyons. As the result, we represent the linear functionality of the free energy of the quark-antiquark pair versus their separation in both non interacting and interacting simulations near the deconfinement temperature. We also show that adding the interaction of dyons to the system increases the string tension and decreases the temperature of the system. In other words, dyonic interaction increases the gluonic field strength.

In this research, the synthesis of strontium aluminate nanoparticles (SrAl2O4) by using of combustion method assisted by microwave and doping them with dysprosium (SrAl2O4:Dy) have been investigated. Characterization of nanoparticles was performed by XRD, FT-IR, EDS, FESEM, UV-Vis and PL. In the synthesis stage, the data of XRDs confirmed the formation of the monoclinic phase of strontium aluminate with space group P1211, in the sample with the fuel to nitrate ratio of 3 to 1, pH value of 5.5, and microwave irradiation time of 5 minutes, calcination time of an hour and calcination temperature of 600 °C. By using the X-ray powder diffraction data and Scherrer's formula, the average size of nanocrystallites was obtained about 26 nm. In the substitution stage, in order to optimize the luminescence of SrAl2O4 nanoparticles, different percentages of doping were investigated. Among the synthesized nanoparticles, the sample of Sr0.9Al2O4: Dy0.1 nanoparticles with the average nanoparticles size 34±3 nm; most frequent distribution of nanoparticles between 30 and 35 nm; optical gap energy equal to 4.21 ± 0.01 eV and with the highest emission intensity in photoluminescence spectrum, was chosen as an optimal sample in terms of the structural and optical properties.

Among the different surface plasmon-based measurement techniques, the detection of phase of surface plasmon is one of the most accurate and sensitive methods. The phase can be measured accurately in different interference based techniques. In this study, the phase and intensity of the surface plasmon was simulated and then the phase shift of surface plasmon wave was experimentally measured by heterodyne polarization interferometry. The response of sensing head to the refractive index change of surrounding medium were obtained. According to the obtained results, the average sensitivity of the phase in the solution of water/alcohol was 0.4426 degree/%gr/ml and for the solution of water/glucose was 1.4765 degree/%gr/ml. The detection limit for solution of water/alcohol and the solution of water/glucose were measured 0.49 %gr/ml and 0.14 %gr/ml, respectively.

In this work, a combined cation of Cesium and Rubidium (RbCsI2) was injected to the main Perovskite solution. The main formulation of the cells was MA0.17FA0.83Pb (I0.83Br0.17)3, hence it contains“ MA” and “FA” cations and also “Br” and “I” anions, which are Halide. The Cesium-Rubidium iodide (RbCsI2) was added to the main solution of Perovskite, while in the control sample only cesium iodide (CsI) was added to the main solution. The two types of fabricated cells were compared according to the current-voltage characteristic (I-V), SEM and XRD tests. Regarding the current-voltage measurements, it was found that the cell efficiency of the cation containing Rubidium-Cesium is higher (0.4 percent) than that of the cell containing just Cesium. SEM images also showed that samples containing Rubidium-Cesium cation have fewer pinholes than Cesium cation on their surface layer. This lead to higher charge transfer and lower trapping of charge carriers, which ultimately increases the cell efficiency. The XRD patterns also show that the precipitate crystallization of the cation containing Rubidium-Cesium is higher than that of cesium cation, which also results in higher transfer rates and thus higher efficiency.

In this paper we intend to determine valence quarks distribution functions u ,d in a wide ‎range of x and Q‏2‏‎, with using experimental data groups such as CCFR, NuTeV, CHORUS ‎and CDHSW , and‏ ‏determine their correlated errors using xFitter framework. We ‎extracted‎ the results for valence quarks distribution functions‎‏ ‏with their uncertainties‎ and ‎compared them with other models. Our results are in agreement with the results of other ‎various models and recent PDG results for strong coupling‏ ‏constant in two approximations ‎NLO and NNLO. The extracted results for valence-quark distributions are in good ‎agreement with available theoretical models.‎

In this paper, the propagation of microwave pulse with Gaussian profile is investigated in the rectangular waveguide filled with plasma in the presence of constant external magnetic field. For this purpose, by using the Maxwell’s equations and the hydrodynamic fluid equations, the differential equation is calculated for the wake potential in the plasma waveguide. In the following, the differential equation is solved by the fourth order Runge-Kutta method, the distribution of the wakefield in the plasma waveguide is simulated by assuming that the pulse duration is equal to the plasma wave duration and the effect of pulse intensity and frequency, waveguide width, plasma density and the magnitude of the external magnetic field are investigated on the pulse propagation in the plasma waveguide and on the wakefield generation. The numerical results show that the microwave wakefield is amplified by increasing the pulse intensity, pulse width and external magnetic field, and decreasing by increasing the plasma density, the pulse frequency and the wavelength. Therefore, by optimizing parameters related to Gaussian pulse and plasma waveguide, creating a strong wakefield can be possible to accelerate the charged particles.

In this paper TiO2 Nanostructures with two different morphologies of naosheet and nanotube are synthesized using chemical vapor deposition and anodize methods. Physical properties of these structures such as morphological, structural and optical are studied using field emission scanning electron microscopy (FESEM), X-ray diffractometer (XRD) and Diffusive reflection spectroscopy (DRS). It is found that TiO2 structures with two different morphologies of nanosheets and nanotubes lead to different optical responses which makes TiO2 nanostructures promissing candidate for possible applications. Therefore, morphological control is obtained using optimum experimental conditions with two different methods, which leads to achieving TiO2 nanostructures with desired physical properties.

In This paper, the production of ZnO nanorods and ZnO/ZnS core/Shell nanorods are reported. The fabricated nanostructures are characterized and studied using different methods including; X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Field Emission Scanning Microscopy (FESM), UV-Visible (UV-Vis) and Photoluminescence (PL) spectroscopy. Results of XRD spectrums clearly show a hexagonal Wurtzite crystal structure for ZnO nanorods and for grown-coated ZnS nanoparticles on ZnO nanorods a cubic Zinc blende crystal structures. The morphology studies of these structures by SEM and FESM have shown the diameters of ZnO nanorods, ZnS nanoparticles, and core/Shell ZnO/ZnS nanorods to be 70, 20 and 120 nanometers, respectively. The absorption spectra of ZnO/ZnS core/Shell compared to ZnO and ZnS structures have clearly shown a shift of absorption band of core/shell structure towards longer wavelengths. This is due to a reduction of efficient band gaps of core/shell structures, as predicted. Results of PL studies have also shown that the coating of zinc oxide nanorods by ZnS nanoparticles decreases some of the structural defects and, consequently, reduces the visible radiation resulting from the structural defect.

Density functional theory (DFT) and many body perturbation theory at the G0W0 level were used to investigate the change of the electron properties of Polythiophene (PT) polymer in the vicinity of graphene. The result of the analysis of the change in the density of the load compared to the pre-mutual interaction indicates a strong electric bipolarity and an absorption of the physical type at the surface. The change in the calculated electrical potential indicates the change in the work function to the value of its initial value . The results from the DFT do not show a change in the polymeric energy gap, while graphene energy gap changes from the isolated chain obtained from the results of the many body perturbation theory at the G0W0 level.

In thid paper, we have investigated numerically optical properties of a periodic array of linked dimer disks based on InSb, in the THz range, by FDTD (finite difference time domain) method. Simulation results show two THz plasmonic modes; charge transfer plasmon mode (CTP) and bonding dipole plasmon (BDP) mode. The CTP mode originates from the conductive junction of linked dimer disks and the BDP mode is due to the coupling of plasmons. It has shown that optical properties of the proposed structure are highly tunable by varying the geometric parameters of the conductive junction. The length reduction of the bridge between dimer disks increases the localized electric field intensity, and the width enhancement of the path way between dimer disks results in the decrement and increment of the amplitudes of the CTP and BDP modes, respectively. The proposed structure is sensitive to polarization angle of incident light in the frequency range of 0.1 to 2.2 terahertz that can be used as polarization switch in THz range. This plasmonic structure can be have significant applications in the field of security, imaging, and spectroscopy in the THz range.

In this research, the thermodynamic stability, Energy of Gap and Electrical conductivity of nano structures of C20 bowl, C20-nSin (n=1-5) and C20-nGen (n=1-5) were investigated at the level of Quantum calculations of LSDA/6-31G of Density Functional Theory (DFT) at the room temperature. We have studied the application of these structures in solar cells. The most stable structures are C15Ge5 and C17Si3 at 300 K. The results show that the substitutes decrease gap of energy and increase the electrical conductivity, but the number of Silicon or Germanium substitute does not have the regular effect on the gap of energy. The C17Ge3 and C16Si4 have the lowest gap of energy and also have more conductivity. The gap of HOMO and LUMO energy levels of the electron donor and electron acceptor components is the most important factor for the electron transfer with photovoltaic application potential. The two structures of C17Si3 as electron acceptor and C15Ge5 as electron donor with the maximum voltage of 1.93 volt can be used in producing solar cell.

In this research, a cost-effective magnetic field sensor with high sensitivity was designed based on thinned optical fiber covered with magnetic fluid. Nano ferrofluid characterized through X-ray diffraction analysis and scanning electron microscopy. The magnetic sensor was prepared by placing the ferrofluid around optical fibers with the same length and different diameters. The effect of fiber diameters on the sensor properties was investigated experimentally. Fiber optic with 0.4 mm in diameter exhibited the highest sensitivity 0.0189 mT/dbm and the widest range of field detection from 2.5 mT to 122.5 mT. The Sensor illustrated linear response around 99% in its optimal performance mode.