Jan M. van Ruitenbeek, Kamerlingh Onnes Laboratorium

Jeudi 31 Janvier 2013, 14h
Amphi Howleck, Esc C, 1ème etage

The Noise is the Signal : Shot Noise as a Tool for Investigating Atomic and Molecular Nanowires

Jan M. van Ruitenbeek
Kamerlingh Onnes Laboratorium, Universiteit Leiden, PO Box 9504, 2300 RA Leiden, The Netherlands

Shot noise is the intrinsic noise in an electron current arising from the discrete character of the electron charge. It carries information on the quantum mechanical electronic structure of nanoscale conductors. In atomic wires shot noise can be exploited for obtaining information on the number of conductance channels and their transmission probability. We have applied shot noise analysis to single-molecule junctions.
The outstanding property that distinguishes a molecule from a quantum dot is its floppy character. This leads to the observation of electron scattering on vibration modes of the molecule, known as Inelastic Electron Tunneling Spectroscopy (IETS). While IETS is now being exploited by many groups for the study and characterization of metal-molecule junctions, the influence of inelastic scattering is expected to affect electron transport more deeply. The conductance can be viewed as the first moment in the probability distribution of a charge q being transmitted through the junction during a given period of time. The second moment is the shot noise in the current. For bias voltages above the vibration mode energy corrections to shot noise have been predicted. We present the first experimental confirmation of these predictions [1] and we argue that the results can be understood in terms of two-electron effects.

[1] M. Kumar, R. Avriller, A. Levy Yeyati, and J.M. van Ruitenbeek, Phys. Rev. Lett. 108, 146602 (2012).

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