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TT: Fachverband Tiefe Temperaturen

TT 32: Transport: Nanoelectronics III - Molecular Electronics 1

TT 32.4: Vortrag

Mittwoch, 28. März 2012, 15:45–16:00, BH 334

Vibrationally dependent electron-electron interactions in single-molecule junctions: A mechanism for asymmetric gate-voltage dependence of the current in symmetrically coupled junctions — •Rainer Härtle, Andre Erpenbeck, and Michael Thoss — Institut für Theoretische Physik, Friedrich-Alexander-Universität, Erlangen-Nürnberg, Staudtstr. 7/B2, D-91058, Germany

The influence of non-adiabatic effects due to vibrationally dependent electron-electron interactions on the transport characteristics of single-molecule junctions is investigated. Non-adiabatic effects in single-molecule junctions result from the dependence of the electronic states of the molecular bridge on the nuclear coordinates. This includes a direct coupling between electronic states, which is important, for example, in the presence of avoided level-crossings or conical intersections, but involves also vibrationally dependent electron-electron interactions. We demonstrate that the latter gives rise to an effective electronic-vibrational coupling, which depends on the population of the electronic states. As a result, the current-voltage characteristics of a single-molecule junction can be asymmetric with respect to a gate voltage, even if the molecular bridge is symmetrically coupled to the leads. To describe these effects, we employ a master equation approach that is based on a second-order expansion in the coupling between the molecule and the leads.