Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 53: Scanning Probe Methods II
O 53.1: Talk
Wednesday, March 13, 2013, 16:00–16:15, H31
Driving a Macroscopic Oscillator with the Stochastic Motion of a Hydrogen Molecule — •Christian Lotze1, M. Corso2, K.J. Franke1, F. v. Oppen1,3, and J.I. Pascual2,4 — 1Freie Universität Berlin — 2CIC nanoGUNE, Donostia-San Sebastián, Spain — 3Dahlem Center for Complex Quantum Systems, Freie Universität Berlin — 4IKERBASQUE, Bilbao, Spain
Tuning Fork based STM/AFM is a well-established method combining the advantages of scanning tunneling and dynamic force microscopy, allowing stable imaging with tip oscillation amplitudes below 1 Å. In this way, conductance and Δ f measurements of molecular junctions can be obtained simultaneously [1] with intramolecular resolution [2].
One of the most intriguing aspects of molecular junctions relates to the effect of structural bi-stabilities in the properties of the junction. These lead, for example, to conductance fluctuations, telegraph noise and the possibility of switching the electrical transport through the junction. In this presentation, we characterize H2 molecules on Cu(111), a model bi-stable molecular system, using dynamic force spectroscopy. The effect of current-induced stochastic fluctuations of conductance is correlated with fluctuations in force. In our experiment, we identified the latter from frequency shift and energy dissipation measurements, picturing a regime in which electrical transport and mechanical motion are coupled in a concerted dynamics that drives the system into self-oscillation [3].
[1] Fournier, et al, PRB 84, 035435 (2011) [2] Gross et al, Science 324, 1428 (2009) [3] C. Lotze et al, Science 338, 779 (2012)