Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 21: Transport: Fluctuations and Noise

TT 21.5: Talk

Tuesday, March 24, 2009, 15:30–15:45, HSZ 304

Phonon assisted noise in molecular junctions — •Federica Haupt¹, Tomas Novotny², and Wolfgang Belzig¹ — ¹Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany — ²Department of Condensed Matter Physics, Charles University, Ke Karlovu 5, CZ-121 16 Praha 2, Czech Republic

Effects due to electron-phonon scattering in molecular junctions are relevant not only because they ultimately affect the characteristics and the stability of the device, but also because they can be used to extract information on the junction itself. In particular, inelastic transport spectroscopy is an important investigation tool for atomic- and molecular devices, and more information is expected to be provided by noise measurements.

In this work we investigate the effects of phonon scattering on the current noise through nanojunctions. Using the extended Keldysh-Green’s function formalism we derive an expression for cumulant generating function in the case of weak electron-phonon coupling. We present analytic results for the case of a single broad level and identify, both in the inelastic current and in the noise, physically distinct contributions based on their voltage dependence. We apply our theory to an experimentally relevant set-up [1] and predict the inelastic contribution to current noise in the presence of phonon heating effects.

[1] R. H. M. Smit, Y. Noat, C. Untied, N.D. Lang, M.C. van Hemert, and J.M. van Ruitenbeek, Nature 419, 906 (2002).