Archivio della ricerca dell'Università di Modena e Reggio Emiliahttps://iris.unimore.itIl sistema di repository digitale IRIS acquisisce, archivia, indicizza, conserva e rende accessibili prodotti digitali della ricerca.Tue, 16 Jul 2019 04:41:24 GMT2019-07-16T04:41:24Z101051Effects of scattering resonances on carrier-carrier entanglement in charged quantum dotshttp://hdl.handle.net/11380/612787Titolo: Effects of scattering resonances on carrier-carrier entanglement in charged quantum dots
Abstract: We address the problem of the entanglement generationin an electron-scattering by a 1D double-barrier resonanttunnelling device. In particular we analyze the roleplayed by transport resonances in the appearance of quantumcorrelations between the energy states of the electrons.The entanglement is not sensitive to the presence of Breit-Wigner resonances, while it may be controlled by manipulatingFano resonances. Such a behavior is ascribed tothe different mechanisms characterizing the two types of processes.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/11380/6127872008-01-01T00:00:00ZQuantum transport of electrons in open nanostructures with the Wigner-function formalismhttp://hdl.handle.net/11380/613149Titolo: Quantum transport of electrons in open nanostructures with the Wigner-function formalism
Abstract: A theoretical Wigner-function approach to the study of quantum transport in open systems in presence of phonon scattering is presented. It is shown here that in order to solve the Wigner equation in its integral form the knowledge of the Wigner function at all points of the phase space at an initial time t0 can be substituted by the knowledge of the same function inside the region of interest at t0 and on its boundary at all times t′ less then the observation time t. The theory has been applied to calculate the current associated with electron quantum transport across given potential profiles and in presence of phonon scattering.
Fri, 01 Jan 1999 00:00:00 GMThttp://hdl.handle.net/11380/6131491999-01-01T00:00:00ZWigner transport equation with finite coherence lengthhttp://hdl.handle.net/11380/1006916Titolo: Wigner transport equation with finite coherence length
Abstract: The use of the Wigner function for the study of
quantum transport in open systems is subject to severe criticisms.
Some of the problems arise from the assumption of
infinite coherence length of the electron dynamics outside
the system of interest. In the present work the theory of
the Wigner function is revised assuming a finite coherence
length. A new dynamical equation is found, corresponding
to move the Wigner momentum off the real axis, and a numerical
analysis is performed for the case of study of the
one-dimensional potential barrier. In quantum device simulations,
for a sufficiently long coherence length, the new formulation
does not modify the physics in any finite region of
interest but it prevents mathematical divergence problems.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/11380/10069162014-01-01T00:00:00ZHot-phonon effect on charge-carrier fluctuations in GaAshttp://hdl.handle.net/11380/617675Titolo: Hot-phonon effect on charge-carrier fluctuations in GaAs
Abstract: We present a Monte Carlo investigation on the influence of a non-equilibrium phonon population (hot phonons) on second order transport properties in GaAs. We calculate the velocity and energy correlation functions both for the case with and without phonon perturbation. The results show significant modifications in the correlation functions and consequently an increase of the equivalent noise temperature due to the presence of hot phonons.
Sat, 01 Jan 1994 00:00:00 GMThttp://hdl.handle.net/11380/6176751994-01-01T00:00:00ZCollision duration for polar optical and intervalley phonon scatteringhttp://hdl.handle.net/11380/617455Titolo: Collision duration for polar optical and intervalley phonon scattering
Abstract: The use of fs laser pulses to excite plasmas in semiconductors has become a major method for studying fast processes. The transition times from the Gamma valley to the satellite X and L valleys are comparable to the reciprocal of the frequency of the phonons involved, bringing into question the use of the standard perturbation-theory approaches. Our aim is to evaluate the time required to emit a phonon, either the intravalley LO or the intervalley, by a nearly-free electron in semiconductors. The leading idea of our work is that the so-called ''collision duration'' is related to the time required to build up correlation between the initial and final state, and then to destroy this correlation as the collision is completed. The calculations are developed using e nonequilibrium Green's function formalism, which allows us to evaluate explicitly the effects of the correlations in time.
Mon, 01 Jan 1996 00:00:00 GMThttp://hdl.handle.net/11380/6174551996-01-01T00:00:00ZEntanglement dynamics of electron-electron scattering in low-dimensional semiconductor systemshttp://hdl.handle.net/11380/2680Titolo: Entanglement dynamics of electron-electron scattering in low-dimensional semiconductor systems
Abstract: We perform the quantitative evaluation of the entanglement dynamics in scattering events between two indistinguishable electrons interacting via the Coulomb potential in one- and two-dimensional semiconductor nanostructures. We apply a criterion based on the von Neumann entropy and the Schmidt decomposition of the global state vector suitable for systems of identical particles. From the time-dependent numerical solution of the two-particle wave function of the scattering carriers we compute their entanglement evolution for different spin configurations: two electrons with the same spin, with different spin, and singlet and triplet spin states. The procedure allows us to evaluate the mechanisms that govern entanglement creation and their connection with the characteristic physical parameters and initial conditions of the system. The cases in which the evolution of entanglement is similar to the one obtained for distinguishable particles are discussed.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/11380/26802006-01-01T00:00:00ZQuantum transport calculations for silicon inversion layers in MOS structureshttp://hdl.handle.net/11380/9316Titolo: Quantum transport calculations for silicon inversion layers in MOS structures
Abstract: We evaluate the mobility of inversion layer electrons in silicon MOSFETs using a real-time Green's functions formalism. Simulation results suggest that interface-roughness considerably affects the low-held mobility, even at room temperature. We also find that an exponential model for the surface-roughness autocorrelation function, as well as Ando's model for the surface-roughness matrix element, leads to the best description of this scattering process over a wide range of inversion charge densities and temperatures. Universal mobility behavior is observed when the proper weighting coefficient for the depletion charge density is used in the definition of the effective field.
Mon, 01 Jan 1996 00:00:00 GMThttp://hdl.handle.net/11380/93161996-01-01T00:00:00ZQuantum transport simulation of the DOS function, self-consistent fields and mobility in MOS inversion layershttp://hdl.handle.net/11380/8305Titolo: Quantum transport simulation of the DOS function, self-consistent fields and mobility in MOS inversion layers
Abstract: We describe a simulation of the self-consistent fields and mobility in (100) Si-inversion layers for arbitrary inversion charge densities and temperatures. A nonequilibrium Green's functions formalism is employed for the state broadening and conductivity. The subband structure of the inversion layer electrons is calculated self-consistently by simultaneously solving the Schrodinger, Poisson and Dyson equations, The self-energy contributions from the various scattering mechanisms are calculated within the self-consistent Born approximation. Screening is treated within RPA, Simulation results suggest that the proposed theoretical model gives mobilities which are in excellent agreement with the experimental data.
Thu, 01 Jan 1998 00:00:00 GMThttp://hdl.handle.net/11380/83051998-01-01T00:00:00ZHot phonons in quantum wells systemhttp://hdl.handle.net/11380/421739Titolo: Hot phonons in quantum wells system
Abstract: We present an investigation of non-equilibrium LO-phonon effects in quantum well systems. Phonon confinement is taken into account by considering esplicitly slab modes in the formulation of Fuchs and Kliever. With respect to the “standard” case, where a tridimensional dispersion is used for the LO phonons, the electron-phonon interaction is riduced as result of phonon confinement. We use the Monte Carlo (MC) scheme, which allows the simultaneous study of the coupled electron and phonon dynamics, without requiring any sort of assumption on the respective distribution function. It should be pointed out that the quantization of the phonon wavevector in the direction perpendicular to the interface completely solves the normalization problems of the hot-phonon calculation in 2D-systems. For the case of photoexcitation in AlGaAs-GaAs quantum wells we observe a reduction in the cooling rate due to the reabsorption of hot phonon.
Sun, 01 Jan 1989 00:00:00 GMThttp://hdl.handle.net/11380/4217391989-01-01T00:00:00ZDynamics of electron-electron entanglement in pulsed sinusoidal potentialshttp://hdl.handle.net/11380/625399Titolo: Dynamics of electron-electron entanglement in pulsed sinusoidal potentials
Abstract: The surface acoustic wave (SAW) assisted charge transport represents a highly controllable mean to inject and drive electrons along quasi one-dimensional channels. By means of a numerical approach, here we analyze the effect of the removal of SAW, for a finite time interval, onto the entanglement stemming from the Coulomb scattering between two charged carriers bound in SAW potential itself. We find that the particles get quickly entangled thus confirming that the SAW driven transport in low-dimensional semiconductor structures permits to suppress the effects of electron-electron correlation due to the Coulomb interaction.
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/11380/6253992009-01-01T00:00:00Z