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HL: Halbleiterphysik
HL 48: Quantenpunke und -dr
ähte: Transporteigenschaften III
HL 48.3: Talk
Thursday, March 27, 2003, 15:45–16:00, BEY/81
Conductance control in carbon based molecular junctions — •Frank Grossmann, Rafael Gutierrez, and Rüdiger Schmidt — Institute for Theoretical Physics, Technical University of Dresden, D-01062 Dresden, Germany
Electron transport across pure carbon devices is studied in the Landauer formalism combined with a density-functional based approach. Two molecular junctions are discussed. In the first junction a C60 molecule is placed between two semi-infinite metallic carbon nanotubes (CNT). We show that the conductance can be tuned within orders of magnitude by changing the orientation of C60 wrt the CNT surface. Additionally, by closing the CNT surfaces with caps, quasilocalized surface states show up in the conductance spectrum as pronounced resonances within the molecular gap. This can be used for conductance control via e.g., a gate voltage. In the second system, electronic transport through cis/trans isomers of stilbene molecules bridging the CNTs is investigated. It is demonstrated that by manipulation of the electrode-molecule interface complete conductance blockade can be attained for both isomers. The effect can be explained by interference of the electronic wave function propagating along different paths on the molecular frame. It suggests a straightforward conductance control mechanism in such molecular systems.