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TT: Fachverband Tiefe Temperaturen

TT 21: TR: Nanoelectronics III - Molecular Electronics 2

TT 21.8: Talk

Tuesday, March 15, 2011, 12:30–12:45, HSZ 301

How Vibrations Generate Electrical Current: Decoherence in Single-Molecule Junctions — •Rainer Härtle, Michael Butzin, and Michael Thoss — Theoretische Festkörperphysik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 7/B2, D-91058 Erlangen, Germany

Employing a nonequilibrium Green’s function approach [1,2], we analyze quantum interference effects and decoherence mechanisms in single-molecule junctions. Quantum interference effects have been found to be of importance in coherent electron transport for different types of nanostructures [3,4], in particular for single-molecule junctions [5]. These effects may result in a suppression of the electrical current due to destructive interference. In the presence of electronic-vibrational coupling, however, this suppression may not fully develop or completely disappears, especially if the vibrational degrees of freedom are highly excited. This is demonstrated for a generic model system and for a realistic model of a biphenyl-acetylene-dithiolate molecular junction, where strong dephasing results from a multitude of vibrational modes. The currents are significantly larger than without electronic-vibrational coupling. In other words, vibrations generate electrical current by quenching of desctructive interference.

[1] R. Härtle et al., Phys. Rev. B 77, 205314 (2008).

[2] R. Härtle et al., Phys. Rev. Lett. 102, 146801 (2009).

[3] B. Kubala, J. König, Phys. Rev. B 65, 245301 (2002).

[4] A. Donarini et al., Phys. Rev. B 82, 125451 (2010).

[5] G. C. Solomon et al., Nano Lett. 6, 2431 (2006).