Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 17: Postersitzung II: Transport, Quantenkoh
ärenz, Quantenflüssigkeiten

TT 17.6: Poster

Dienstag, 9. März 2004, 14:30–19:00, Poster A

Coulomb blockade in benzol-dithiol: DFT calculations — •M. Koentopp, F. Evers, and F. Weigend — Institut für Nanotechnologie, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany

For the development of future molecular-electronics devices an important prerequisite is the ability to realize molecular switches, i.e. changing the conductance properties of a molecule in a controlled fashion. A major recent achievement has been the observation of Coulomb blockade in single organic molecules by applying a gate voltage (S. Kubatkin et al., Nature 425, 698-701 (2003)).

Here, we report theoretical calculations on the Coulomb blockade for a paradigmatic system, namely the molecule 1,4 benzol-dithiol. We use the nonequilibrium Green’s function formalism in combination with density functional calculations with the program package TURBOMOLE. The number of atoms in the simulated electrodes is large enough to ensure that Fermi level mismatch does not occur. The gate is realized by point charges distributed homogenously on a square grid in a plane parallel to the C-atoms. Charging effects are included in a manner that in principle is exact. Screening of the gate by the electrodes (charge neutrality) is thereby taken fully into account.

We observe the expected shift of the transmission resonances with increasing gate voltage. These shifting levels lead to spikes in the transmission when they cross the Fermi energy.