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On the non-orthogonality problem in the description of quantum devices
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. (Condensed Matter Theory group)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. (Condensed Matter Theory group,)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. (Condensed Matter Theory Group)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. (Condensed Matter Theory Group)
1999 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 272, no 1-4, p. 28-30Article in journal (Refereed) Published
Abstract [en]

An approach which allows to include the corrections from non-orthogonality of electron states in contacts and quantum dots is developed. Comparison of the energy levels and charge distributions of electrons in 1D quantum dot (QD) in equilibrium, obtained within orthogonal (OR) and non-orthogonal representations (NOR), with the exact ones shows that the NOR provides a considerable improvement, for levels below the top of barrier. The approach is extended to non-equilibrium states. A derivation of the tunneling current through a single potential barrier is performed using equations of motion for correlation functions. A formula for transient current derived by means of the diagram technique for Hubbard operators is given for the problem of QD with strongly correlated electrons interacting with electrons in contacts. The non-orthogonality renormalizes the tunneling matrix elements and spectral weights of Green functions.

Place, publisher, year, edition, pages
1999. Vol. 272, no 1-4, p. 28-30
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-90019DOI: 10.1016/S0921-4526(99)00343-9OAI: oai:DiVA.org:uu-90019DiVA, id: diva2:162039
Available from: 2002-10-11 Created: 2002-10-11 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Non-Orthogonality and Electron Correlations in Nanotransport: Spin- and Time-Dependent Currents
Open this publication in new window or tab >>Non-Orthogonality and Electron Correlations in Nanotransport: Spin- and Time-Dependent Currents
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The concept of the transfer Hamiltonian formalism has been reconsidered and generalized to include the non-orthogonality between the electron states in an interacting region, e.g. quantum dot (QD), and the states in the conduction bands in the attached contacts. The electron correlations in the QD are described by means of a diagram technique for Hubbard operator Green functions for non-equilibrium states.

It is shown that the non-orthogonality between the electrons states in the contacts and the QD is reflected in the anti-commutation relations for the field operators of the subsystems. The derived forumla for the current contains corrections from the overlap of the same order as the widely used conventional tunneling coefficients.

It is also shown that kinematic interactions between the QD states and the electrons in the contacts, renormalizes the QD energies in a spin-dependent fashion. The structure of the renormalization provides an opportunity to include a spin splitting of the QD levels by polarizing the conduction bands in the contacts and/or imposing different hybridizations between the states in the contacts and the QD for the two spin channels. This leads to a substantial amplification of the spin polarization in the current, suggesting applications in magnetic sensors and spin-filters.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2002. p. 101
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 756
Keywords
Physics, non-orthogonality, non-equilibrium, transport, nanosystem, quantum dot, spin-dependent, renormalization, Green function, diagram technique, many-body states, Hubbard operator, electron correlations, time-dependent, Fysik, icke-ortogonal, icke-jämvikt, transport, nanosystem, kvantprick, spinberoende, renormering, Green-funktion, diagramteknik, mångkropparstillstånd, Hubbadoperator, elektronkorrelationer, tidsberoende
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-2687 (URN)91-554-5418-6 (ISBN)
Public defence
2002-11-01, Polhemssalen, Uppsala, 10:15
Opponent
Available from: 2002-10-11 Created: 2002-10-11 Last updated: 2012-03-18Bibliographically approved

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Fransson, JonasEriksson, OlleJohansson, Börje

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