Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 35: Postersession Transport: Nanoelectronics, Quantum Coherence and Quantum Information, Fluctuations and Noise
TT 35.21: Poster
Mittwoch, 25. März 2009, 14:00–18:00, P1A
Electron induced heating and molecular phonon cooling in single C60 junctions — Gunnar Schulze, Katharina J. Franke, and •Jose Ignacio Pascual — Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
The functionality of single molecules as electronic devices relies on its stability against large current densities. Electronic current generates heat in the molecular junction due to coupling of electrons with molecular vibrations. Using a scanning tunnelling microscope operated at 5 K, we thermally decompose single C60 molecules on a metal surface by passing current through them, and investigate the response of the degrading current (and power) to changes in electron energy. The power for decomposition results from the balance between heating and cooling efficiencies [1]. We find that heating varies with electron energy and reflects the molecular resonance structure participating in the transport. Through inelastic electron spectroscopy measurements, we identify those vibrations which are mostly excited when tunneling through the LUMO state, confirming that symmetry selection rules apply here. Cooling, on the other hand, is a non-resonant process, dominated by the decay of molecular vibrations into electron-hole pair excitations. We find that the partial occupation of molecular states enhance the molecular cooling due to an enhancement of density of states at the molecule-metal interface [2].
[1] G. Schulze, et al., Phys. Rev. Lett. 100, 136801 (2008)
[2] G. Schulze, et al., N. J. Phys. 10, 065005 (2008)