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Öğe Comment on "Electric field effect on the second-order nonlinear optical properties of parabolic and semiparabolic quantum wells"(AMER PHYSICAL SOC, 2005) Karabulut, I; Atav, U; Safak, HZhang and Xie [Phys. Rev. B 68, 235315 (2003)] presented their results for the second harmonic generation (SHG) susceptibility in electric-field-biased parabolic and semiparabolic quantum wells (QW's). In this Comment, we demonstrate that the results presented for the SHG coefficient in a parabolic QW with an applied electric field are not physically sound and they contradict with well-established properties of the Hermite polynomials which just happen to be the wave functions describing such a system. It is shown that in a parabolic QW with an applied electric field intersubband transitions contribute to neither second nor any higher order harmonic generation.Öğe Electronic properties of a large quantum dot at a finite temperature(ELSEVIER SCIENCE BV, 2005) Gulveren, B; Atav, U; Tomak, MThe physical properties of a two-dimensional parabolic quantum dot composed of large number of interacting electrons are numerically determined by the Thomas Fermi (TF) method at a finite temperature. Analytical solutions are given for zero temperature for comparative purposes. The exact solution of the TF equation is obtained for the non-interacting system at finite temperatures. The effect of the number of particles and temperature on the properties are investigated both for interacting and non-interacting cases. The results indicate that the effect of e e interaction on the density profile shows different temperature dependencies above and below a certain temperature T-c. (c) 2005 Elsevier B.V. All rights reserved.Öğe A parabolic quantum dot with N electrons and an impurity(ELSEVIER SCIENCE BV, 2005) Gulveren, B; Atav, U; Sahin, M; Tomak, MGround-state properties of a two-dimensional quantum dot composed of N electrons and an impurity are investigated by the Thomas-Fermi (TF) method at T = 0. The changes induced by the impurity in electron density, chemical potential and total energy are calculated. Calculations are also performed for different number of particles and strength of confinement. The results indicate that Thomas-Fermi approximation is applicable even when the system contains only a few particles. (c) 2005 Elsevier B.V. All rights reserved.Öğe Quantum genetic algorithm method in self-consistent electronic structure calculations of a quantum dot with many electrons(WORLD SCIENTIFIC PUBL CO PTE LTD, 2005) Sahin, M; Atav, U; Tomak, MIn this study, we have calculated energy levels of an N-electron quantum dot. For this purpose, we have used two different techniques, matrix diagonalization and quantum genetic algorithm, to obtain simultaneous solutions of the coupled Schrodinger and Poisson equation in the Hartree approximation. We have determined single particle energy levels, total energy, chemical potential and capacitive energy. We have also compared the results, demonstrated the applicability of QGA to many-electron quantum systems and evaluated its effectiveness.Öğe VMC calculations of the ground state properties of nuclear matter(WORLD SCIENTIFIC PUBL CO PTE LTD, 2005) Manisa, K; Atav, U; Ogul, RA Variational Monte Carlo method (VMC) is described for the evaluation of the ground state properties of nuclear matter. Equilibrium properties of symmetric nuclear matter and neutron matter are calculated by the described VMC method. The Urbana v(14) potential is used for the nucleon-nucleon interactions in the calculations. Three- and more-body interactions are included as a density dependent potential term. Total, kinetic and potential energies per particle axe obtained for nuclear and neutron matter. Pressure values of nuclear and neutron matter are also calculated at various densities. The binding energy of nuclear matter is found to be -16.06 MeV at a saturation density of 0.16 fm(-3). The results obtained are in good agreement with those obtained by various authors with different potentials and techniques.
