Browsing by Author "Kulik, Igor O."

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Open Access
ABC: a double-conversion compiler/solver for nanoscience calculus
(Computational Publications, 2003) Kulik, Igor O.
"CompLab" ("Compiler Laboratory") or "ABC" ("Advanced Basic-C") is a double conversion compiler working in two parallel regimes (A and B) one of which is similar to that of MATLAB while the other is a professional compilation routine similar to C and FORTRAN languages. Double-conversion scheme of compilation allows making advantage of both the simplicity of used code (program, commands) and at the same time of the power of C language in speed and in the capacity of CPU memory usage. The "A" regime allows for on-line calculation of multidimensional integrals, eigenvalues of large matrices, roots of nonlinear equations, plotting functions and their derivatives, etc. The "B" regime is an exportable program of conversion from the pseudobasic input code to C-code, compilation and solution. The C-code is fit for usage in any computational platform including Windows, OS/2, Linux and Unix machines.
Open Access
Aharonov-Bohm effect induced by light
(Springer, Dordrecht, 1998) Kulik, Igor O.; Shumovsky, Alexander S.; Hunter, G.; Jeffers, S.; Vigier, J. -P.
The quantum interferometry of normal metallic loops based on the Aharonov-Bohm effect is usually applied to measurements at low temperatures in the case of static or slowly time-varying magnetic fields (e.g., see [1]). Recently, an important case of an ac field of high frequency ω » v F /R (v F is the Fermi velocity and R is the radius of the metallic ring) has been considered [2]. This consideration is based on the assumption that the position dependent time-varying electromagnetic field produces the static electron energy minibands in the ring which appear due to electron motion in a time-averaged electrostatic potential periodic with coordinate along the ring circumference, produced by the square of an ac electric field [3]. it should be noted that, in the quantum case, an electron reflection from an oscillating potential causes a time-dependent phase shift, resulting in an effective chaotization of the phase of electron wave function, except at energy multiples of ħω.
Open Access
Non-decaying currents in normal metals
(Springer, 2000) Kulik, Igor O.; Kulik, Igor O.; Ellialtioğlu, Recai
In a present paper, we review cases when stable, time-independent currents may flow in normal metals, both single-connected or multiple-connected, in presence of magnetic field or the field of vector potential. These include the spatially oscillating currents in narrow metallic stripes originating due to Landau diamagnetism (the Landau persistent currents), the currents in hollow normal-metal or semiconducting cylinders and rings induced by the Aharonov-Bohm flux threading the conducting loop (the Aharonov-Bohm persistent currents), and currents in hollow cylinders subject to radial flux and existing even in the absence of the longitudinal, or Aharonov-Bohm flux (the “transverse” persistent currents), as well as the non-decaying currents in axial magnetic field, modulated via the Berry phase effect by the transverse or azimuthal components of the field and oscillating as a function of the latter.
Open Access
Nonlinear phenomena in metallic contacts
(Springer, 2000) Kulik, Igor O.; Kulik, Igor O.; Ellialtioğlu, Recai
We review and extend theoretical approaches to nonlinear and nonequilibrium effects in metallic microcontacts ranging in their dimension from the atomic to macroscopic sizes. Atomic contacts are shown to quantize their conductance in units of 2e2/h provided the charge redistributes near the constriction to establish the maximal electron transmittivity through the orifice. Ballistic semiclassical contacts are treated both from the Landauer point of view and from the Boltzmann transport theory. The J-V nonlinearity in contacts is related to the inelastic scattering near the narrowest part of the constriction and permits for spectroscopic investigation of phonons in solids (the point-contact spectroscopy).The effects of phonon emission and reabsorption in contacts are taken into consideration. Phonon relaxation is shown to determine the frequency dependence of the nonlinear contact conductivity. Thermal contacts develop specific nonequilibrium states with hot spots in the center of metallic constriction whose temperature is much in excess of the ambient contact temperature and is uniquely related to voltage.
Open Access
Persistent current and persistent charge in nanostructures
(Springer, 1997) Kulik, Igor O.; Hakioğlu, Tuğrul; Shumovsky, Alexander S.
Quantúm effects in the interaction of electromagnetic field with small, but not microscopically small, metallic particles and rings are investigated. The aspects of mesoscopic systems related to time-independent (or magnetic) Aharonov-Bohm effect, time-dependent (electric) Aharonov-Bohm effect, and to quantum high-frequency effects in a coupled system: optical fiber+ mesoscopic conducting loop are discussed.
Open Access
Persistent current in a mesoscopic ring with strongly coupled polarons
(Springer, 2000) Bayındır, Mehmet; Kulik, Igor O.; Kulik, Igor O.; Ellialtıoğlu, Recai
We investigate influence of the electron-phonon interaction on persistent current in a mesoscopic ring threaded by a Aharonov-Bohm flux Φ. We find that all thermodynamic quantities are still periodic in Φ with a period Φo = hc/e. In both cases, weak- and strong-coupling, effective mass of the electrons is increased and amplitude of persistent current is suppressed. In the latter case the amplitude decreases exponentially as a function of the electron-phonon coupling constant.
Open Access
Persistent currents in mesoscopic loops and networks
(TÜBİTAK, 2003) Kulik, Igor O.
The paper describes persistent (also termed "permanent", or "non-decaying") currents in mesoscopic metallic and macromolecular rings, cylinders and networks. The current arises as a response of system to Aharonov-Bohm flux threading the conducting loop and does not require external voltage to support the current. Magnitude of the current is periodic function of magnetic flux with a period of normal-metal flux quantum Φ 0 = hc/e. Spontaneous persistent currents arise in regular macromolecular structure without the Aharonov-Bohm flux provided the azimuthal periodicity of the ring is insured by strong coupling to periodic background (a "substrate"), otherwise the system will undergo the Peierls transition arrested at certain flux value smaller than Φ 0. Extremely small (nanoscopic, macromolecular) loop with three localization sites at flux Φ = Φ 0/2 develops a Λ-shaped energy configuration suitable to serve as a qubit, as well as at the same as a "qugate" (quantum logic gate) supporting full set of quantum transitions required for universal quantum computation. The difference of the Aharonov-Bohm qubit from another suggested condensed-matter quantum computational tools is in the radiation free couplings in a qubit supporting the scalable, long-lived quantum computation.
Open Access
Preface
(Springer, 2000) Kulik, Igor O.; Ellialtıoğlu, Recai; Kulik, Igor O.; Ellialtıoğlu, Recai
Open Access
Quantum computation with persistent-current Aharonov-Bohm qubits and qugates
(Computational Publications, 2003) Kulik, Igor O.
We analyse the possibility of employing mesoscopic or nanoscopic rings of a normal metal in a double degenerate persistent-current state in the presence of the Aharonov-Bohm flux equal to the half flux quantum as entangled quantum bits of information (qu-bits). The third level in a three-state qubit can be effectively used to coherently couple the qu-bit to logical gates for the reversible NOT (in a single qu-bit) and CNOT (in two coupled qu-bits) operations. Further we suggest that a (hypothetic) crystal implementing conducting ring-shaped molecules, or triples of anionic vacancies (similar to F 3-centers in alkali halides) with one trapped electron, in crossed magnetic and electric fields satisfies the requirements of the proposed mechanism and may serve as a new kind of device for universal quantum computation.
Open Access
Superconductivity in ultrasmall metallic particles
(Springer, 2000) Boyacı, Hüseyin; Gedik, Zafer; Kulik, Igor O.; Kulik, Igor O.; Ellialtıoğlu, Recai
Recent single electron transport experiments in nanometer size samples renewed the question about the lower limits of the size of superconductors, and the crossover from superconducting to normal state. In order to give answers to these questions, a pairing Hamiltonian for fixed number of particles is studied including the degeneracy of levels around the Fermi energy. For d-fold degenerate states we find that the ratio of two successive parity parameters Δ p is nearly 1 + l/d.