Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 88: Electronic structure II
O 88.5: Talk
Friday, March 30, 2012, 11:30–11:45, MA 043
Low-Energy Scale Excitations in the Spectral Function of Organic Monolayer Systems — •Achim Schöll1,2, Johannes Ziroff1,2, Simon Hame1,2, Mario Kochler1,2, Azzedine Bendounan1,2, and Friedrich Reinert1,2 — 1Experimentelle Physik VII und Wilhelm Conrad Röntgen Research Center for Complex Material Systems, Universität Würzburg, 97074 Würzburg, Germany — 2Gemeinschaftslabor für Nanoanalytik, Karlsruher Institute für Technologie KIT, 76021 Karlsruhe, Germany
Using high-resolution photoemission spectroscopy we demonstrate that the electronic structure of several organic monolayer systems, in particular 1,4,5,8-naphthalene tetracarboxylic dianhydride and Copper-phtalocyanine on Ag(111), is characterized by a peculiar excitation feature right at the Fermi level. This feature displays a strong temperature dependence and is immediately connected to the binding energy of the molecular states, determined by the coupling between the molecule and the substrate. At low temperatures, the line-width of this feature, appearing on top of the partly occupied LUMO (lowest unoccupied molecular orbital of the free molecule), amounts to only ~ 10meV, representing an unusually small energy scale for electronic excitations in these systems. We discuss possible origins, related e.g. to many-body excitations in the organic-metal adsorbate system, in particular a generalized Kondo scenario based on the single impurity Anderson model.