14 research outputs found
Low-Energy Scale Excitations in the Spectral Function of Organic Monolayer Systems
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 immediatly
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 lowest
unoccupied molecular orbital of the free molecule, amounts to only
meV, 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.Comment: 6 pages, 3 figures, accepted as PRB Rapid Communication