Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 14: Transport: Nanoelectronics III - Molecular Electronics

TT 14.8: Talk

Tuesday, February 26, 2008, 11:30–11:45, H 3010

Current switching in single molecule transport and contact — •Velimir Meded, Alexej Bagrets, Andreas Arnold, and Ferdinand Evers — Institute of Nanotechnology, Research Centre Karlsruhe, Hermann-von-Helmholtzplatz 1, 76344 Eggenstein-Leopoldshafen, Germany

Two experiments measuring the current-voltage characteristics (IV) of the bipyridine-dinitro-dithiole-system found that the molecule can be controllably switched between two states exhibiting significantly different IV curves [1,2]. To better understand the nature of the bistable state we have performed ab initio calculations. They indicate, that molecular charging/uncharging does not lead to bistability in the presence of electrodes. By contrast, two (or more) energy minima can arise with conformational changes of the molecule alone or in the molecule-contact region (possibly combined with structural relaxations in a larger contact area). As a prototypical example of such a mechanism, we consider rotations of the molecule about the axis defined by the two anchoring Au-atoms. From an extensive analysis of possible contact structures, we conclude that bistable configurations can indeed arise for slightly disordered, i.e. realistic, contacts -- though they do not appear to be generic. A scenario will be proposed, how in this light experimental findings might be understood. (We are indebted to E. Loertscher, H. Riel and M. Ruben for instructive discussions.)

[1] Z. K. Keane, J. W. Ciszek, J. M. Tour, and D. Natelson, Nano Lett., Vol. 6, No. 7, 2006. [2] E. Lörtscher, J. W. Ciszek, J. Tour, and H. Riel, Small 2, 973 (2006).