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The Kondo effect in nanoelectronic devices, e.g. single electron transistors or carbon nanotubes, has attracted attention because tunable model systems allow systematic investigations of complex many-body effects in electronic structure and electron transport. It has also been observed in single-molecule experiments which are used to study electrical transport in the quantum limit. Far reaching tunability of the transport physics on the one hand and optimum structural control of the transport junction on the other are the object of many of these experiments. In the present contribution we present a single-molecule transport experiment in which the combination of tunability and atomic-scale control reaches a very high level. We start with a well-characterized chemical bond between a π-conjugated molecule and a single crystalline metal surface (PTCDA/Ag(111)), because this type of contact is important for organic and molecular electronics, contact the molecule with the STM tip at a distinct functional group, retract the tip and thus mechanically vary the molecule-substrate contact in wide bounds from chemisorption via weak interaction (Kondo regime) to bond cleavage. The tunable electronic transport spectra thus recorded reveal minute details about the bond breaking process itself and the many-body transport physics in the molecular wire [1].
[1] R. Temirov and S. Tautz. cond-mat/0612036.
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