Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 14: Symposium Molecular Electronics

TT 14.2: Hauptvortrag

Dienstag, 28. März 2006, 10:00–10:30, HSZ 02

Three-terminal transport through molecular junctions — •Herre van der Zant — Kavli Institute of Nanoscience, Lorentzweg 1, 2628 CJ Delft, The Netherlands

With electrochemical etching and electromigration, nanogaps on an aluminum gate have been made and small organic molecules of different lengths have been trapped between the electrode pairs. Temperature-dependent transport measurements as a function of gate voltage show that the molecules are weakly coupled to the leads. Samples with the same molecule share common features. For some molecular systems, we find that at low temperatures smaller molecules are worse conductors than longer ones. Asymmetric junctions with a sulphur-gold bonding only on one side, exhibit current-voltage characteristics with steps that are absent for symmetric ones. Coulomb blockade measurements on OPV-3 and OPV-5 show excited states and Kondo behavior. The excitations are associated with vibrational modes and a very good correspondence with Raman spectra is found. Excitations in the single-molecule magnet Mn-12 (S = 10 ground state) are related to non-degenerate spin states. Negative differential resistance and complete current suppression at low bias are explained by a new kind of spin blockade.