Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 26: Transport - Poster Session

TT 26.28: Poster

Mittwoch, 29. März 2006, 14:30–18:30, P1

Molecular conductance from ab initio calculations: self energies and absorbing boundary conditions — •Andreas Arnold¹ and Ferdinand Evers² — ¹Institut für Theorie der kondensierten Materie, Universität Karlsruhe, 76128 Karlsruhe, Germany — ²Institut für Nanotechnologie, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany

Calculating an exact self energy for ab initio transport calculations relevant to Molecular Electronics can be troublesome. Errors or insufficient approximations made at this step are a frequent reason why many molecular transport studies become inconclusive. We propose a simple and efficient approximation scheme, that follows from interpreting the self energy as an absorbing boundary condition of an effective Schroedinger equation. Our approximation is controlled by a small parameter, which essentially is the inverse number of electrode atoms, that are kept in the ab initio calculation.

The method is illustrated using a tight binding wire as a toy model, for which an analytical solution is available, against which we can check our numerical results. Also more realistic applications for transport calculations based on the density functional theory have been performed. They yield results in very good agreement with the conventional way to set up the electronic self energy.