Regensburg 2007 – wissenschaftliches Programm

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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 7: Single Molecule Contacts

SYOE 7.1: Hauptvortrag

Dienstag, 27. März 2007, 16:30–17:15, H32

Electronic spectrum and spin states of a single organic molecule — •Herre van der Zant — Kavli Institute of Nanoscience, Delft, The Netherlands

With electromigration nanogaps on an aluminum gate electrode have been made and single molecules have been trapped between the electrode pairs. Three-terminal measurements on samples with the same molecule (OPV-5, Co4L4 grid molecule, Mn-12, single-metal atom complexes) share common features showing Coulomb blockade and Kondo physics at low temperature. Of crucial importance is the observation of molecule-specific properties as deduced for example from the interaction between electronic transport and vibrational modes or spin states in the molecule. Transport through an individual thiol end-capped oligophenylenevinylene molecule with five benzene rings (OPV-5) has been studied in great detail and displays more than fifteen excitations in the differential low-temperature conductance map. Their energies agree with the ones from optical measurements and are attributed to vibrational modes of the molecule. A consistent set of measurements shows that the spin states, the charging energies and the electronic spectrum are completely renormalized by the presence of the gold electrodes. In case of the doubly charged molecule the data indicate delocalized orbitals with an antiferromagnetic ground state and an exchange of 1.7 meV.

Molecules are provided by Thomas Bjørnholm (OPV-5, single-metal atom complexes), M. Ruben and J.-M. Lehn (Co4L4 grid molecules) and A. Cornia (Mn-12).