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Friday, 23 January 2015

Dr. Richard Korytar presented an ICN2 Seminar about metal-organic interfaces for molecular electronics

The speaker reviewed two interesting experiments that shed light on the complexity of metal-organic interfaces, in a talk offered at ICN2 on January 16. Dr. Nicolas Lorente, from the ICN2 Theory and Simulation Group, presented the Seminar.

One of the intriguing features of molecular electronics is the invasive character of electrodes on the atomic scale. Therefore, it is often necessary to backup experimental studies by theoretical insights. Dr. Richard Korytar, from the Universität Regensburg (Germany), reviewed two interesting experiments that shed light on the complexity of metal-organic interfaces, in a talk offered at ICN2 on January 16. Dr. Nicolas Lorente, from the ICN2 Theory and Simulation Group, presented the Seminar.

Dr. Korytar talked about single-molecule (vinylenedipyridine) junctions bonded by either silver or gold electrodes. The results of the calculations he presented show how band-structure differences between the two electrode materials influence the width of molecular resonances.

The second study was motivated by silver break-junction experiments with copper phthalocyanine, a spinfull molecule. Here, spin fluctuations give rise to a Kondo resonance in the differential conductance. The calculations he explained establish the connection of the inelastic signal to the vibrational excitation (breathing mode) of the molecule. A comparison with earlier studies with phthalocyanines on silver surfaces reveals that the way the molecule is contacted (on-surface vs in a junction) has a crucial role: the molecular spin and low-lying excitations are entirely different.

In the last part, Dr. Korytar focused on the spectra of oligoacenes. These molecules are one of the simplest realization of carbon-based nanowires or zig-zag terminated graphene nano-ribbons. The speaker demonstrated that the optical gap as a function of the molecular length shows surprising oscillations with period approx. 11 rings. By using state-of-the-art exact many-body analysis the speaker proposed that these oscillations can be measured for molecules adsorbed on metallic surfaces.