Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 41: Inorganic/Organic Interfaces
O 41.30: Poster
Dienstag, 17. März 2015, 18:15–21:00, Poster B
Quantum interference in tunneling through a molecular Kondo system — Isabel Fernandez-Torrente1, •Michael Ruby1, Tobias R. Umbach1, Benjamin W. Heinrich1, Jose I. Pascual2, and Katharina J. Franke1 — 1Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 2CIC nanoGUNE and Ikerbasque, Basque Foundation for Science, Tolosa Hiribidea 78, Donostia-San Sebastian 20018, Spain
The Kondo effect results from a virtual spin scattering process between an unpaired spin of a magnetic impurity and the surrounding spins of the conduction electrons. This leads to a sharp resonance around zero bias in Scanning Tunneling Spectroscopy (STS) spectra at the location of the unpaired spin. Its line-shape depends on the interference between different tunneling pathways in the tip-impurity-surface junction. It is described by a Lorentzian curve for the case of a preferential tunneling into the Kondo state, and shows an increasing asymmetry for higher contributions of direct tunneling paths into the surface.
A prerequisite to study the variation of the line-shape in a molecular network is to have a single electron in a delocalized orbital. An ideal model system for this is a charge transfer monolayer formed by Na atoms and TNAP (tetracyanonaphtoquinodimethane) molecules on an Au(111) surface. The electron donated by the Na atoms is localized in the singly occupied molecular orbital (SOMO) of the acceptor TNAP. We observed intramolecular changes in the shape and intensity of the resonance along the TNAP backbone, with a symmetry change at the nodal planes of the SOMO.