Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 8: Posters Transport
TT 8.24: Poster
Freitag, 4. März 2005, 14:00–18:00, Poster TU C
Thermopower of single-molecule devices — •Jens Koch1, Felix von Oppen1, Yuval Oreg2, and Eran Sela2 — 1Institut für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin — 2Department of Condensed Matter Physics, Weizmann Institute for Science, Rehovot 76100, Israel
We investigate the thermopower of single molecules weakly coupled to metallic leads. We model the molecule in terms of the relevant electronic orbitals and phonons corresponding to either internal vibrations or to oscillations of the molecule as a whole. The thermopower is computed by means of rate equations including both sequential-tunneling and cotunneling processes.
The sign of the thermopower reveals whether electronic transport through the molecule occurs via the LUMO or the HOMO. It is found that the thermopower is sensitive to higher-order processes such as cotunneling. Under certain conditions, it allows one to access the electronic and phononic excitation spectrum of the molecule in a linear-response measurement. In particular, we find that phonon features are more pronounced for weak lead-molecule coupling.