1,720,967 research outputs found
Multiband, non-parabolic Wigner-function approach to electron transport in semiconductors
No full textIn this work, we introduce a multiband transport model for quantum electron transport in semiconductors following the Wigner-function approach. By using the Bloch-Floquet decomposition of the density matrix, we obtain the Bloch-Floquet projections of the Wigner function and derive their evolution equations for energy bands of arbitrary shape. The equations of the model are very general and allow (in principle) the investigation of quantum processes in which interband transitions and/or non-parabolicity effects may occur. Finally, we present numerical applications for some particular cases in which the numerical solution can be obtained easily
Numerical simulation of an intervalley transition by the Wigner-function approach
No full textIn this work we present a recently developed transport model, based on the Wigner-function approach and allowing for non-parabolic band profiles. Two scattering mechanismIs are included by means of a Boltzmann-like collision operator, describing the collisions between electrons and polar optical and intervalley phonons. The transport equation for the Wigner function is solved by the splitting-scheme algorithm. We have chosen a one-dimensional model band profile, which exhibits satellite valleys, besides the minimum at the centre of the Brillouin zone, similar to the band profile of GaAs
Non-parabolic electron transport in semiconductors by the Wigner-function approach
No full textThe Wigner function approach to electron transport in semiconductors is commonly used to describe the properties of electronic devices. Until now, this approach was restricted to the description of the conduction band electrons, under the effective-mass approximation. A multi-band, non-parabolic transport model has been introduced; numerical results for multi-band transport have been obtained until now only for very elementary examples and more extensive numerical work is underway; numerical results for non-parabolic, single-band transport have been more numerous and easier to obtain, so this aspect has been studied in more detail. We shall illustrate some of the results in this symposium
NUMERICAL AND ANALYTICAL APPLICATIONS OF MULTIBAND TRANSPORT IN SEMICONDUCTORS
No full textA multiband transport model for electron transport in semiconductors, based on the Wigner-transport approach and allowing for energy bands of arbitrary shape, is presented and applied to two simple examples: a comparison of exact and free streaming solutions of teh Wigner equation in non-parabolic regime and an interband transition in an infinite homogeneous medium
Wigner function for multiband transport in semiconductors
No full textIn this work we present a one-dimensional model of quantum electron transport in semiconductors that makes use of the Wigner function formalism and that takes into account the full band structure of the medium for energy bands of any shape. We introduce a multi-band Wigner function and derive the evolution equations for each component, with and without external fields, by using a Bloch states representation of the density matrix
Wigner-function approach to multiband transport in semiconductors
No full textIn this work we present a one-dimensional, multi-band model for electron transport in semiconductors that makes use of the Wigner-function formalism and that allows for energy bands of any shape. A simplified two-band model is then derived from the general equations, by using the parabolic band approximation
Floquet projections of a Gaussian Wigner function in a Kroning-Penney potential
No full textIn this contribution, we apply the multiband model developed in \cite{ref3} to a Kronig-Penney potential and calculate the Floquet projections of a Gaussian Wigner function in phase space. The Bloch functions are calculated numerically and then used in the expressions of the Wigner projections
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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