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Quantum integrability of 1D ionic hubbard model
, Article Annalen der Physik ; Volume 532, Issue 3 , 2020 ; Jafari, S. A ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
The quantum integrability of the 1D ionic Hubbard model (IHM) is established using two independent numerical methods, namely i) energy level spacing statistics and ii) occupation profile of one-particle density matrix (OPDM) eigen-values. Both methods suggest that the 1D IHM is integrable. The calculations of energy level statistics reproduce the known results for the standard Hubbard model. Upon turning on the the ionic term, the energy level spacing distribution of this model continues to obey the Poissonian distribution. Occupation patterns as extracted from OPDM indicate that quasi-particles are sharpened upon increasing the ionic potential. This is evidenced by a larger jump in the...
Vortex bound states of charge and magnetic fluctuations induced topological superconductors in heterostructures
, Article Physical Review B ; Volume 100, Issue 14 , 2019 ; 24699950 (ISSN) ; Kargarian, M ; Sharif University of Technology
American Physical Society
2019
Abstract
The helical electron states on the surface of topological insulators or elemental bismuth become unstable toward superconducting pairing formation when coupled to the charge or magnetic fluctuations. The latter gives rise to pairing instability in chiral channels dxy±idx2-y2, as has been observed recently in the epitaxial Bi/Ni bilayer system at relatively high temperature, while the former favors a pairing with zero total angular momentum. Motivated by this observation we study the vortex bound states in these superconducting states. We consider a minimal model describing the superconductivity in the presence of a vortex in the superconducting order parameter. We show that zero-energy...
Transition of d -level quantum systems through quantum channels with correlated noise
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 75, Issue 4 , 2007 ; 10502947 (ISSN) ; Golshani, M ; Sharif University of Technology
2007
Abstract
Entanglement and entanglement assisted are useful resources to enhance the mutual information of the Pauli channels, when the noise on consecutive uses of the channel has some partial correlations. In this paper, we study quantum-communication channels in d -dimensional systems and derive the mutual information of the quantum channels for maximally entangled states and product states coding with correlated noise. Then, we compare fidelity between these states. Our results show that there exists a certain fidelity memory threshold, which depends on the dimension of the Hilbert space (d) and the properties of noisy channels. We calculate the classical capacity of a particular correlated noisy...
Time dependence of magnetization in Fe1-xCox fine particles
, Article 4th International Conference on Magnetic and Superconducting Materials, MSM'05, Agadir, 5 September 2006 through 8 September 2006 ; Volume 3, Issue 9 , 2006 , Pages 3220-3224 ; 18626351 (ISSN) ; Seht, S. A ; Akhavan, M ; Sharif University of Technology
2006
Abstract
The change of the applied field in a medium containing anisotropic magnetic grains, makes the number of magnetic moments in the field direction, and in the opposite direction to vary. Near H = Hc, probability of transition between the two minimum energies (SW model) increases strongly and the magnetization of system varies rapidly. We measured the time dependence of magnetization for various Fe1-xCOx samples, in the presence of some step fields. These samples were grown via solving iron, and cobalt salts with borohydride and then, heat treatment was accomplished on them. The results of time measurement of magnetization in step fields reveals a linear proportionality between coercivity and...
Phase-noise measurement using two inter-injection-locked microwave oscillators
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 54, Issue 7 , 2006 , Pages 2993-3000 ; 00189480 (ISSN) ; Banai, A ; Farzaneh, F ; Sharif University of Technology
2006
Abstract
Phase noise in two mutually coupled oscillators is analyzed by the describing function method, and the after-lock phase noise of the oscillators is calculated in terms of their free-running phase noise. A new phase-noise measurement technique based on inter-injection locking of two similar oscillators is proposed. Experimental results are presented, which confirm the theory. It is shown that in the case of zero phase of coupling coefficient, the system is in the optimum state where the only required parameter for the measurement is the locking bandwidth. In this optimum state, as far as the locking bandwidth is measured correctly, imperfections such as the frequency drift, parameters...
A new method in prediction of TCP phases formation in superalloys
, Article Materials Science and Engineering A ; Volume 396, Issue 1-2 , 2005 , Pages 138-142 ; 09215093 (ISSN) ; Bahrami, A ; Sharif University of Technology
2005
Abstract
The purpose of this investigation is to develop a model for prediction of topologically closed-packed (TCP) phases formation in superalloys. In this study, artificial neural networks (ANN), using several different network architectures, were used to investigate the complex relationships between TCP phases and chemical composition of superalloys. In order to develop an optimum ANN structure, more than 200 experimental data were used to train and test the neural network. The results of this investigation shows that a multilayer perceptron (MLP) form of the neural networks with one hidden layer and 10 nodes in the hidden layer has the lowest mean absolute error (MAE) and can be accurately used...
Influence of energy band alignment in mixed crystalline TiO2 nanotube arrays: Good for photocatalysis, bad for electron transfer
, Article Journal of Physics D: Applied Physics ; Volume 50, Issue 50 , 2017 ; 00223727 (ISSN) ; Sharif University of Technology
Abstract
Despite the wide application ranges of TiO2, the precise explanation of the charge transport dynamic through a mixed crystal phase of this semiconductor has remained elusive. Here, in this research, mixed-phase TiO2 nanotube arrays (TNTAs) consisting of anatase and 0-15% rutile phases has been formed through various annealing processes and employed as a photoelectrode of a photovoltaic cell. Wide ranges of optoelectronic experiments have been employed to explore the band alignment position, as well as the depth and density of trap states in TNTAs. Short circuit potential, as well as open circuit potential measurements specified that the band alignment of more than 0.2 eV exists between the...
Anderson Localization of Electromagnetic Waves
, Ph.D. Dissertation Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
The electrons scatter by the impurities during propagation through the media and become localized by increasing the impurities. So the metal insulator transition occurs. This phenomenon was first proposed by W. Anderson and is known as Anderson Localization. In this thesis the Anderson localization of electromagnetic waves is investigated. The disordered media with random dielectric constant is studied by considering Maxwell’s equations. There are different numerical methods to study this phenomenon such as transfer matrix method and level statistics we have used in this thesis. In three dimension, different scaling behavior shows the phase transition from localized states to extended states...
Studying of one Particle Gap and Hubbard Parameter Competition in one Dimension Using the Bethe Ansatz Method
, Ph.D. Dissertation Sharif University of Technology ; Jafari, Akbar (Supervisor)
Abstract
The ionic Hubbard model is an extended version of the Hubbard model in which an ionic potential term is added to the original Hubbard model. This model was proposed to describe the neutral-ionic transition in the charge transfer of salts, and later attention to this model increased due to its potential application in ferroelectric perovskites. Considering the realization of the ionic Hubbard model in cold atoms in the study of the invention of superlattice modulation spectroscopy to investigate the bond order and a very attractive recent study for the realization of the one-dimensional ionic Hubbard model in the twisted GeSe bilayer, existence of an exact solution and accurate results for...
Pressure dependence of effective Coulomb interaction parameters in BaFe2As2 by first-principle calculation
, Article Physica C: Superconductivity and its Applications ; Volume 548 , 15 May , 2018 , Pages 61-64 ; 09214534 (ISSN) ; Hadipour, H ; Akhavan, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Pressure dependence of the onsite Coulomb interactions of the BaFe2As2 has been studied by employing the constrained random phase approximation within first-principle calculations. Analyzing total and projected density of states, a pseudogap is found for dxy band at the energy roughly 0.25 eV higher than the Fermi level. Also, by applying pressure the spectral weight of the dxy orbital vanishes while other orbitals remain metallic. The different screening channels, as discussed in four different models, affect significantly on the Hubbard U while the Hund J remains almost unchanged. The average onsite bare and partially and fully screened Coulomb interactions increase with different rates...
Mimicking the Hadamard discrete-time quantum walk with a time-independent Hamiltonian
, Article Quantum Information Processing ; Volume 18, Issue 5 , 2019 ; 15700755 (ISSN) ; de Oliveira, M. C ; Sharif University of Technology
Springer New York LLC
2019
Abstract
The discrete-time quantum walk dynamics can be generated by a time-dependent Hamiltonian, repeatedly switching between the coin and the shift generators. We change the model and consider the case where the Hamiltonian is time-independent, including both the coin and the shift terms in all times. The eigenvalues and the related Bloch vectors for the time-independent Hamiltonian are then compared with the corresponding quantities for the effective Hamiltonian generating the quantum walk dynamics. Restricted to the non-localized initial quantum walk states, we optimize the parameters in the time-independent Hamiltonian such that it generates a dynamics similar to the Hadamard quantum walk. We...
X-ray photoemission studies of Zn doped Cu1-xTlxBa2Ca2Cu 3-yZnyO10-δ (y = 0, 2.65) superconductors
, Article Physica C: Superconductivity and its Applications ; Volume 453, Issue 1-2 , 2007 , Pages 46-51 ; 09214534 (ISSN) ; Mumtaz, M ; Ahadian, M. M ; Iraji zad, A ; Sharif University of Technology
2007
Abstract
The X-ray photoemission (XPS) measurements of Cu1-xTlxBa2Ca2 Cu3-yZnyO10-δ (y = 0, 2.65) superconductors have been performed and compared. These studies revealed that the charge state of thallium in the Cu0.5Tl0.5Ba2O4-δ charge reservoir layer in Zn doped samples is Tl1+, while it is a mix of Tl1+ and Tl2+ in Zn free samples. The binding energy of Ba atoms in the Zn doped samples is shifted to higher energy, which when considered along with the presence of Tl1+ suggested that it more efficiently directed the carriers to ZnO2 and CuO2 planes. The evidence of improved inter-plane coupling witnessed in X-ray diffraction is also confirmed by XPS measurements of Ca atoms in the Zn doped samples....
Interaction of quantum dot molecules with multi-mode radiation fields
, Article Scientia Iranica ; Volume 17, Issue 1 D , 2010 , Pages 59-70 ; 10263098 (ISSN) ; Naqavi, A ; Khorasani, S ; Sharif University of Technology
2010
Abstract
In this article, the interaction of an arbitrary number of quantum dots behaving as artificial molecules with different energy levels and a multi-mode electromagnetic field is studied. We make the assumption that each quantum dot can be represented as an atom with zero kinetic energy, and that all excitonic effects except dipole-dipole interactions may be. disregarded. We use the. Jaynes-Cummings-Paul model with applications to quantum systems based on a time-dependent Hamiltonian and entangled states. We obtain a system of equations describing the interaction, and present a method to solve the equations analytically for a single mode fi,eld within the Rotating-Wave Approximation. As an...
Leak detection in water-filled plastic pipes through the application of tuned wavelet transforms to Acoustic Emission signals
, Article Applied Acoustics ; Volume 71, Issue 7 , 2010 , Pages 634-639 ; 0003682X (ISSN) ; Sharif Bakhtiar, M ; Sharif University of Technology
2010
Abstract
A new method to detect leakage in a water-filled plastic pipe is proposed. In this method, a leakage signal-signature in time domain is first captured by monitoring the Short Time Fourier Transforms (STFT) of AE (Acoustic Emission) signals over a relatively long time-interval. The captured signal is then used to find a mother wavelet (tuned wavelet) for the best signal localization in time and frequency domains. The technique for AE signal detection using tuned wavelet is then described. Practical application of the method proposed herein is then presented using a water-filled plastic pipe as a case study. Signals generated from this experimental setup are collected to identify leakage...
Recent results of edge plasma parameters measurements in IR-T1 tokamak by probe
, Article Journal of Fusion Energy ; Volume 29, Issue 3 , June , 2010 , Pages 271-274 ; 01640313 (ISSN) ; Emami, M ; Ghoranneviss, M ; Abaspour Tehrani Fard, A ; Sharif University of Technology
2010
Abstract
Langmuir probes (LP) are the most common diagnostics for the local measurement of very important plasma parameters such as plasma density, electron temperature, plasma potential and the electron energy distribution function (EEDF). In this paper the applicability of the first derivative Langmuir probe method in processing the electron part of the current-voltage (I-V) characteristics in IR-T1 Tokamak is reported. The EEDF at different radial positions in the edge region and Scrape off Layer (SOL) are derived and the values of the plasma potential, electron temperature and electron density are estimated. Results comparison between the first derivative method and Stangeby method shows a...
Potential and energy of the monoenergetic electrons in an alternative ellipsoid bubble model
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 81, Issue 2 , 2010 ; 10502947 (ISSN) ; Rahmatallahpur, S ; Sharif University of Technology
Abstract
The electron acceleration in the bubble regime is considered during the intense laser-plasma interaction. The presented ellipsoid cavity model is more consistent than the previous spherical model, and it explains the monoenergetic electron trajectory more accurately. At the relativistic region, the maximum energy of electrons in the ellipsoid model is about 24% more than the spherical model, and this is confirmed by PIC and the measured experimental results reported here. The electron energy spectrum is also calculated, and it is found that the energy distribution ratio of electrons ΔE/E for the ellipsoid model in the here reported condition is about 11% which is less than the one third that...
Optimization of CuIn1-XGaXS2 Nanoparticles and Their Application in the Hole-Transporting Layer of Highly Efficient and Stable Mixed-Halide Perovskite Solar Cells
, Article ACS Applied Materials and Interfaces ; Volume 11, Issue 34 , 2019 , Pages 30838-30845 ; 19448244 (ISSN) ; Marandi, M ; Khosroshahi, R ; Malekshahi Byranvand, M ; Dehghani, M ; Zad, A. I ; Tajabadi, F ; Taghavinia, N ; Sharif University of Technology
American Chemical Society
2019
Abstract
Inorganic hole-transport materials (HTMs) have been frequently applied in perovskite solar cells (PSCs) and are a promising solution to improve the poor stability of PSCs. In this study, we investigate solution-processed copper indium gallium disulfide (CIGS) nanocrystals (NCs) as a dopant-free inorganic HTM in n-i-p type PSCs. Moreover, Cs0.05(MA0.17-FA0.83)0.95Pb(I0.83Br0.17)3 mixed-halide perovskite with proper crystalline quality and long-time stability was utilized as the light-absorbing layer under ambient conditions. To optimize the cell performance and better charge extraction from the perovskite layer, the Ga concentration in the Cu(In1-XGaX)S2 composition was changed, and the X...
Evolution of quantum electronic features with the size of silicon nanoparticles embedded in a sio2 layer obtained by low energy ion implantation
, Article 11th International Autumn Meeting on Gettering and Defect Engineering in Semiconductor Technology, GADEST 2005, 25 September 2005 through 30 September 2005 ; Volume 108-109 , 2005 , Pages 71-76 ; 10120394 (ISSN); 9783908451136 (ISBN) ; Shalchian, M ; Benassayag, G ; Coffin, H ; Bonafos, C ; Dumas, C ; Atarodi, S. M ; Claverie, A ; Pichaud B ; Claverie A ; Alquier D ; Richter H ; Kittler M ; Richter H ; Kittler M ; Sharif University of Technology
Trans Tech Publications Ltd
2005
Abstract
In this paper, we have studied the evolution of quantum electronic features with the size of silicon nanoparticles embedded in an ultra-thin SiO2 layer. These nanoparticles were synthesized by ultralow energy (1 KeV) ion implantation and annealing. Their size was modified using the effect of annealing under slightly oxidizing ambient (N2+O2). Material characterization techniques including transmission electron microscopy (TEM) Fresnel imaging and spatially resolved electron energy loss spectroscopy (EELS) have been used to evaluate the effects of oxidation on structural characteristics of nanocrystal layer. Electrical transport characteristics have been measured on few (less than two...
Minimizing the levelized cost of energy in an offshore wind farm with non-homogeneous turbines through layout optimization
, Article Ocean Engineering ; Volume 249 , 2022 ; 00298018 (ISSN) ; Khorasanchi, M ; Sayyaadi, H ; Sadollah, A ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Minimum cost of energy is the main goal of a wind farm layout optimization. This is achieved by maximizing the total energy while minimizing the total costs of the farm. In this study, two sizes of commercial turbines were considered to investigate the effect of a non-homogenous farm on the layout optimization process. A cost model consisting of turbines, cable, transformers, foundation, and service vehicle routes was developed. Using Genetic Algorithm and Artificial Neural Network, first the superiority of the new algorithm in turbines and cable layout was verified versus previous studies. Next, two cases were investigated, i.e. (1) a farm populated with identical turbines and (2) a farm...
Benchmarking of Monte Carlo model of Siemens Oncor® linear accelerator for 18MV photon beam: determination of initial electron beam parameters
, Article Journal of X-Ray Science and Technology ; Volume 27, Issue 6 , 2 January , 2020 , Pages 1047-1070 ; Hoseini Ghafarokhi, M ; Bolagh, R. S. M ; Haghparast, M ; Zarifi, S ; Nickfarjam, A ; Farhood, B ; Chow, J. C. L ; Sharif University of Technology
IOS Press
2020
Abstract
OBJECTIVE: This study aims to benchmark a Monte Carlo (MC) model of the 18 MV photon beam produced by the Siemens Oncor® linac using the BEAMnrc and DOSXYZnrc codes. METHODS: By matching the percentage depth doses and beam profiles calculated by MC simulations with measurements, the initial electron beam parameters including electron energy, full width at half maximum (spatial FWHM), and mean angular spread were derived for the 10×10 cm2 and 20×20 cm2 field sizes. The MC model of the 18 MV photon beam was then validated against the measurements for different field sizes (5×5, 30×30 and 40×40 cm2) by gamma index analysis. RESULTS: The optimum values for electron energy, spatial FWHM and mean...