Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 40: TR: Nanoelectronics III: Molecular Electronics 2
TT 40.5: Talk
Friday, March 26, 2010, 12:30–12:45, H20
Density-functional study of transmission channel degeneracy in biphenyl-based single-molecule junctions — •M. Bürkle1, F. Pauly1, J.K. Viljas1, and G. Schön1,2 — 1Institut für Theoretische Festkörperphysik, KIT, 76128 Karlsruhe, Germany — 2Institut für Nanotechnologie, KIT, 76128 Karlsruhe, Germany
Using density functional theory, we investigate the charge transport for a series of biphenyl molecules [1]. The torsion angle between the two phenyl rings, and hence the degree of π conjugation is controlled by alkyl chains and methyl side groups. Considering different bonding geometries, we find that the conductance can vary by one order of magnitude for the same molecule [2]. We explain this by the different hybridisation of molecular states with those of the electrode. For all molecules, except for those with completely broken conjugation, we observe that the transmission is dominated by one channel, formed from the π electrons. For molecules with D2d point group symmetry at 90∘, two degenerate transmission channels should dominate the transport. However, in the molecular junction the electrodes reduce the symmerty and destroy the channel degeneracy. We show that for bonding geometries with a small degree of hybridisation between the electrode and the molecule, nevertheless, the channel degeneracy presists .
[1] A. Mishchenko, D. Vonlanthen, V. Meded, M. Bürkle, C. Li, I.V. Pobelov, A. Bagrets, J.K. Viljas, F. Pauly, F. Evers, M. Mayor, and T. Wandlowski, Nano Lett. (in press).
[2] M. Bürkle, F. Pauly, J.K. Viljas, V. Meded, A. Bagrets, and G. Schön (submitted).