مجله پژوهش فیزیک ایران
سال نوزدهم شماره 3 (پاییز 1398)

In this article, we present a brief and elementary review of quantum thermodynamics and its achievements and challenges. This review includes an introduction to some fundamental concepts such as internal energy, heat, work, entropy, entropy production, thermal equilibrium, second law of quantum thermodynamics, relation between thermodynamics and information theory, as well as a discussion of how quantum effects such as entanglement and correlations affect performance of quantum heat engines.

In this paper, we have studied the photonic band structure of function photonic crystals in which the dielectric constant of the scattering centers (rods) is a function of space coordinates. The under-studied lattice is hexagonal and cross section of rods has a circular symmetry embedded in the air background. Photonic band structures for both electric and magnetic polarizations of the electromagnetic waves are calculated. The obtained results show the existence of the forbidden frequency region (photonic band gap). It is considered that the dielectric rods are made of the Kerr type materials. Therefore, by considering different distributions of light intensity, different function forms will be obtained for the dielectric constants of rods, which are called function photonic crystals. The influence of the function coefficient (corresponding to the Kerr coefficient) on photonic band structures has been theoretically investigated. The results show that the width and number of photonic band gaps are more controllable than the conventional photonic crystals. These results can be very useful in designing the optical devices.

Quantum fisher information of a parameter characterizing the sensitivity of a state with respect to parameter changes. In this paper, we study the quantum fisher information of the W state for four, five, six and seven particles in decoherence channels, such as amplitude damping, phase damping and depolarizing channel. Using Krauss operators for decoherence channels components, we investigate the quantum fisher information quite analytically. We observe that for the W state, the amount of the quantum fisher information and consequently, the amount of entanglement are reduced by applying the quantum noises, which affect each particle in the same way. In some cases, a relative increase appears in the quantum fisher information for certain values of the decay strength p. We also show that the phase damping channel vanishes the value of the quantum fisher information for the W state.

The Elko spinor field is a spin 1/2 fermionic quantum field with a mass dimension introduced as a candidate of dark matter. In this work, we study the localization of Elko fields on a de Sitter thick brane constructed by a canonical or phantom scalar field. By presenting the mass-independent potentials of Kaluza-Klein (KK) modes in the corresponding Schrödinger equations, it is shown that the Elko spinor field with a five- dimensional mass term can be localized on de Sitter branes. Also, by using a Yukawa type coupling term, we find that the Elko spinor field can be localized on this brane with a particular coupling constant. Furthermore, it is shown that the zero mode of the  Elko field is localized on the de Sitter brane through a Yukawa geometrical coupling term.

Nowadays, nuclear instruments are being widely used in various scientific and industrial fields. Different types of nuclear radiations (alpha, beta, and gamma) can be used in the construction of these gauges. Gamma based densitometers, as non-contact and non-destructive test tools, are favorably being used for process monitoring in various industries, such as oil and petrochemical industries. Design and construction of a gamma ray density gauge and measurement of temperature dependence of water density via this gauge have been reported in this study. The results indicate that the designed device can measure the temperature dependence of water density with good accuracy.

The Random Deposition model is the simplest model for surface growth, where there is no correlation between the neighbor sites of the lattice. In the Ballistic deposition model, the particles stick to the first neighbor particle; thus it is used to describe the deposition of the sticky particles. However, in many true-life phenomena involving surface growth, there is no adhesion. Instead, the friction between the particles leads to interlocking particles and the formation of porosity inside the growing bulk. Presenting a discrete 1+1 dimensional model, we study this case. In this model, if a particle is trapped between two other particles from right and left, it will stay in that position, as an equivalent for friction. The growth and roughness exponents are calculated, close to the Ballistic model, although there is no lateral growth.

The possibility of inserting an optical klystron on the storage ring of an Iranian Light Source Facility as a Synchrotron Radiation Free electron Laser for coherence harmonic generation in the soft x-ray spectrum has been studied. The study has been performed using the 3D FEL simulation code GENESIS 1.3 and in accordance with the available characteristic parameters of ISLF. Different potential schemes together with their output and characteristics are discussed.

A major source of energy dissipation and surface wear is the kinetic friction at the interfaces of sliding bodies. Traditionally, on a macroscopic scale, this undesirable effect is reduced with lubricating the surfaces by introducing oil into their interface. An interesting phenomenon, called superlubricity, has been reported on a nanometer scale where dry (without lubricant oil) fruition and wear become very low. In contrast, interlocking between the crystalline surfaces at such length scales may lead to a high frictional state called stick-slip motion. We study the transition between these two frictional states by modeling the surface of one object as a chain of particles coupled harmonically to each other and to the object body and interacting with the other object via a sinusoidal potential. The amplitude of the sinusoidal potential corresponds to the normal load at the interface. Our calculations show that the transition takes place at some critical amplitude of the potential which, like the average contribution of each particle to the kinetic friction force, is practically independent of the contact size.

In the present work, the triple and double cross sections of atomic hydrogen ionization in collision with the proton are  calculated. The potential of the interaction is considered as a Coulombic;  also,  the first and second order Born approximations have been used. The singularity of the Green operator in the second order approximation has been removed for the analytical solution of the scattering amplitude and the triple cross section calculation. Finally, the results for triple and double cross sections have been compared with the available theoretical and experimental results. The first and the second Born approximations are usually applied at intermediate and high impact energy ranges. However, it is  shown that it could be successfully applied at lower energies as well.

In this paper, we introduce ubergravity based on the idea of the ensemble average theory of f (R) gravity models. This model has interesting properties including its universality. Another property of this model is its curvature dependency: In high curvatures, ubergravity is reduced to standard Einstein-Hilbert action, while in low curvatures, it vanishes. This transition happens at a scale of R0. It is possible to show that this dimensionful scale plays the role of the cosmological constant at late times. To consider the behavior of the non-linear structure formation, we need to start with the spherical collapse; hence, here we study the spherically symmetric solutions. We show that the radius dependency of these solutions is totally different from the Schwarzchild solution. Interestingly, the solutions looks like the Reissner-Nordstrom in the absence of any electrical charge.

In this work, a (ZnO)/(Cu-doped ZnO) core/shell nanorods array was fabricated by a two-step ZnO hydrothermal synthesis followed by encapsulation via a dip-coating process. The effects of the Cu dopant concentration on the structural, electrical and optical properties of the nanorods were studied. The SEM images showed that the encapsulation increased the nanorods average diameter from ~40 to ~60 nm. All ZnO core/shell nanorods showed a hexagonal wurtzite structure with no trace of a Cu oxide phase. A peak shift was observed in the XRD pattern, indicating the better Cu+ substitution into the Zn sites. The I–V measurements also showed that Cu doping up to 4.5 at.% decreased the samples resistance, which could be attributed to the +1 valance state of the Cu ions. It was also found that Cu doping increased the UV photoresponsivity of the photodetectors made by Cu:ZnO.

The interaction between two ring polymer chains located in the area between two dimensional channel walls is investigated using molecular dynamics simulation. One monomer of each chain is fixed at an equal distance from each of the channel walls. The simulations show that the force between the two polymers is repulsive; on average, irrespective of the channel thickness, it decreases with the increase of the distance between the two fixed monomers. In addition, the force applied to the channel walls by the geometrical fluctuations of the polymers is also repulsive, regardless of the distance between the two fixed monomers, such that, on average, it is decreased with the cubic inverse of the channel thickness.

The effects of the inhomogeneous magnetic field on the quantum discord of the thermal state of a two-qubit isotropic Heisenberg system is investigated. The results show that the inhomogeneity of the magnetic field could remove the degeneracy of the left and right quantum discord. The results of this paper are important for the process of quantum state preparation

Harmonic oscillator is significantly important in quantum gravity for its dynamical properties. Dynamics of the harmonic oscillator can be modified by inserting a modified uncertainty relation considered in quantum cosmology models such as string theory and quantum loop gravity theory. In this paper, the equation of damped quantum harmonic oscillator has been solved with respect to the modified uncertainty relation and the effects of this modification have been probed in the case of the damped oscillating system.

In this research, a new algorithm is proposed to automatically extract the effective parameters on the radial velocity curves of the binary stars systems using the Wilson-Devnney (WD) 2007 code. In this regard, a binary star which has the proximity effect and its parameters are also announced by astronomers, is selected as the sample system. To avoid scattering of data and also to have more data point, the radial velocity curve of the sample binary stars is first made using the WD code. Then, the code output data is introduced to the proposed MATLAB algorithm to find the effective parameters on the radial velocity curve, including the eccentricity e, the product of a semi-major axis and orbital inclination asini, center of mass radial velocity VCM, the longitude of periastron ω, And surface parameters of stars such as surface potentials Ω, temperatures T, albude A, gravitational darkening coefficients g, and limb darkening coefficients x. After testing the algorithm on the sample binary stars system, the proposed algorithm is also exploited to analyze the radial velocity data of some other binary stars such as U Peg, AB And, and BD+422782. Comparison between the results obtained from the proposed approach and the results reported by other astronomers demonstrates the ability of the proposed approach in extracting the parameters effective on the radial velocity curves.

The cold spot is one of the observed CMB anomalies proposed to be produced by various primary and secondary effects. In this work, we study the gravitational lensing of some of the candidates that could produce the cold spot, namely a huge void and a cosmic texture, on the various components of CMB random field. Our results demonstrated that the signal to noise ratio of gravitational lensing effect on the CMB temperature field is higher than that of on CMB polarization. We found that for a cylindrically symmetric void at z_Void=0.8 with σ=-1.0   a thousand minute observation would detect the gravitational lensing signal while for a cosmic texture at z_Texture=6.0 a longer observation is required. We expect the future high resolution surveys can put strong constraints on the amplitudes of the template of these models.

The interaction of ionizing radiations with living tissues could result in simple and complex single- and double-strand breaks in the cell DNAs, due to the physical and chemical processes that such radiations initiate. Monte Carlo simulation of the interaction between radiations and DNA renders valuable information about damage types, which can be very useful in cancer therapy and radiation protection. In this study, in order to calculate the initial DNA damage caused by the primary electron beam and the produced secondary particles, Geant4-DNA has been employed to simulate the physical, physico-chemical, and chemical interactions. Using the simulation results for the direct electron interactions and indirect hydroxyl radical reactions with the DNA, the probability of different types of breaks in the cell DNAs as well as the distribution of the breaks as a function of the deposited energy have been investigated.

In this study, the aim has been the interpretation of the measured x-ray spectrum for kaonic atoms (Z>2) in various elements and compounds. Initially, kaon capture probability in the compounds is calculated and compared by different atomic models. By using Mont-Carlo method, the atomic cascade dynamic of atoms is simulated and the yield of each transition is obtained. By using the fitting method for each atom, the optimum parameters of the two models for the initial angular momentum distribution are extracted. The Z-dependence of these parameters confirms the Condo' hypothesis concern regarding the correlation between the size of atom and the initial angular moment of atom that lead to the periodic behavior of X-ray yields. By comparing the yields and its ratios with the measured values, a good agreement in the most of cases is obtained.

In this paper, high-order harmonic generation by a bicircular field, which consists of two coplanar counterrotating circularly polarized fields of frequency ω and 3ω, is investigated for bromine (Br2) molecule. This field possesses dynamical symmetry, which can be adapted to the symmetry of the highest occupied molecular orbital (HOMO) and used to investigate the molecular symmetry. An accurate three dimensional(3D) calculation of molecular dynamics through time dependent density- functional theory (TDDFT)is considered to explore broad harmonic plateau with high efficiency. We show that an attosecond pulse with a pulse duration of 349as  from the superposition of several optimum harmonics is generated.  Furthermore, in order to study of the quantum trajectory of electrons, time-frequency analysis is utilized. This work is proved to be a potential way for applications in coherent imaging and photoelectron spectroscopy.

This paper studies the structural, optical and ultraviolet photodetection of rutile titanium dioxide nanorods (TiO2). A regular array of relatively vertically aligned TiO2 nanorods has been grown on fluorine doped tin oxide (FTO) coated glass substrate by using one step hydrothermal synthesis method. The morphology and crystal structure were studied by scanning electron microscopy and X- ray diffraction, respectively. Photoluminescence (PL) and diffuse reflectance spectroscopy were used as experimental methods for band gap energy estimation of nanostructures. The room temperature Photoluminescence spectra were measured under two different excitation energies of 4.13 and 3.82 eV. The results indicate the dependence of the PL spectrum to excitation energy. Thus, the band gap energy of nanorods is approximately equal to 3.04 eV and observed in the PL spectrum under 4.13 eV excitation energy. Comparing the applied reported methods for calculating the band gap energy by using diffuse reflectance spectra and Kubelka- Munk method shows that the most relevance to PL data exist with application of  equation. The ultraviolet photodetection performance of TiO2 nanorods in  Au/TiO2/Au device structure under 365 nm illumination is evaluated by determining resposivity, sensivity and rise and decay tims.

We calculated the drag force for asymptotically Lifshitz space times in (d+ 2)-dimensions with the arbitrary dynamical exponent z. We find that at zero and finite temperature, the drag force has a non-zero value. Using the drag force calculations, we investigate the DC conductivity of the strange metals.

In this paper, we investigate the entanglement teleportation of a two-qubit state under XYZ Heisenberg interaction in a cavity using the Jaynes-Cummings model. We analyze the channel entanglement, output entanglement and fidelity as a function of decoherence rate and spin coupling constant. We find that the teleportation is more effective if we take the proper initial input state.

In this study, CdS films prepared using the technique of pyrolysis spray at the glass and Si wafer with a thickness of 300 nm using Cadmium Acetate Cd (CH3COO)2·2H2O with purity of 99.6% and Thiourea (CS(NH2)2) with purity 99.6%. These compounds are used as the sourced materials of Cd+2 and S-2 ions, respectively for the CdS films formation. The films were annealed at different temperatures (400, 500, and 600 0C), then the effect of annealing on its properties was studied. The high-quality films were obtained as evident using XRD analysis. X-ray diffraction analysis for all CdS films was polycrystalline with cubic and hexagonal wurtzite structure with preferential orientation in the H (002) and C (111) direction. It is difficult to distinguish between them, after high-temperature process from 400 0C to 6000C, new peaks of the hexagonal structure appeared. This phenomenon was thought to be the phase change of CdS thin film by heat treatment as well as the increasing of intensity of H (002) and decreases in full width at half maxima (FWHM) the grains size with annealing. The CdS photodetector and the spectral response of CdS/Si junction was studied. The maximum value of responsivity occurred at a wavelength of 500 nm to 560 nm. The maximum values of D* and η at Ta equal to 500 0C. Whereas, they increase and shift to higher wavelength with the increase of Ta. It has been observed that the best spectral response occurs when the annealing temperature equal to 500 0C, therefore, is essential to say that this value of Ta was the optimum condition for prepared CdS photoconductive detector.

Tungsten oxide (WO3) thin layers were prepared on Fluorine Tin Oxide glass by electrodeposition method. WO3 layers were evaluated as a function of the deposition time (480s, 600s, 660s and 720s).SEM results show that by increasing the deposition time, gradual decrement in cracks on their surface will occur. The electrochromic properties of the WO3 thin layers were investigated in a nonaqueous LiClO4–PC electrolyte by means of optical transmittance, cyclic voltammogram (CV) measurements. The WO3 thin layer with deposition time 600s exhibits a noticeable electrochromic performance with a variation of transmittance up to 58.26% at 633nm. The CV measurements reveal that the WO3 thin layer with deposition time 600s has high electrochemical reaction activity and reversibility due to its highly porous structure.