Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 14: Transport: Nanoelectronics III - Molecular Electronics

TT 14.10: Vortrag

Dienstag, 26. Februar 2008, 12:00–12:15, H 3010

Symmetry effects in transport properties of benzene quantum dots — •Georg Begemann, Dana Darau, Andrea Donarini, and Milena Grifoni — Theoretische Physik, Universität Regensburg

We investigate electronic transport through a benzene molecule quantum dot. In particular, we investigate the influence of the contacts' position and find qualitative and quantitative differences between the para- and the meta configurations.

The Hamiltonian of the interacting isolated molecule is diagonalized and its eigenstates are classified according to their particle number, spin and symmetry representation.

Treating the coupling to the leads perturbatively, a generalized master equation for the reduced density matrix in the benzene's eigenbasis is derived, which includes coherences between degenerate eigenstates. We explicitly demonstrate that the coherences do not contribute to the linear transport, but become essential for the meta-configuration in the nonlinear regime.

Analytic expressions for the linear conductance and the current in the low bias regime agree with numeric calculations, where we are not restricted to small voltages. Interesting features appear over a wide range of gate and bias voltages, for example, due to the reduced symmetry of the problem, negative differential conductance is present in the meta-configuration, while it is absent in the para-configuration.