Dresden 2009 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 23: Transport: Nanoelectronics III - Molecular Electronics
TT 23.1: Talk
Wednesday, March 25, 2009, 09:30–09:45, HSZ 105
Length-dependent conductance and thermopower in single-molecule junctions of dithiolated oligophenylene derivatives: A density functional study — •Fabian Pauly1,2, Janne Viljas1,2, and Juan Carlos Cuevas3 — 1Institut für Theoretische Festkörperphysik, Universität Karlsruhe, Germany — 2Forschungszentrum Karlsruhe, Institut für Nanotechnologie, Germany — 3Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Spain
We study theoretically the length dependence of both conductance and thermopower in metal-molecule-metal junctions made up of dithiolated oligophenylenes contacted to gold electrodes [1]. We find that while the conductance decays exponentially with increasing molecular length, the thermopower increases linearly as suggested by recent experiments [2]. We also analyze how these transport properties can be tuned with methyl side groups. Our results can be explained by considering the level shifts due to their electron-donating character as well as the tilt-angle dependence of conductance and thermopower. Qualitative features of the substituent effects in our density functional calculations are explained using a tight-binding model. In addition, we observe symmetry-related even-odd transmission channel degeneracies as a function of molecular length.
[1] F. Pauly, J. K. Viljas, and J. C. Cuevas, Phys. Rev. B 78, 035315 (2008).
[2] P. Reddy, S.-Y. Jang, R. A. Segalman, and A. Majumdar, Science 315, 1568 (2007).