Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 24: Symposium Nanomechanics

TT 24.3: Fachvortrag

Dienstag, 8. März 2005, 11:25–12:00, TU H104

Some Quantum Phenomena in Nanoelectromechanical Systems — •Jörg P. Kotthaus — Department für Physik and Center for NanoScience, LMU München

In an effort to create a single electron shuttle we study a nanoelectromechanical system (NEMS) etched out of Si and containing a metallic island which driven by Coulomb forces mechanically oscillates and transfers charge between two contacts. With increasing ac bias we find in the dc current a transition from charge transport via normal tunneling to transport via field emission from the isolated nanoscale island. It deviates in a characteristic fashion from the usual Fowler Nordheim description of field emission [1]. GaAs-based NEMS containing a low-dimensional electron gas are fabricated suitably to enable the definition of an individual quantum dot within a suspended beam. The low temperature electron transport through such a suspended quantum dot is found to exhibit a new characteristic gap in the diamond-like conductance spectra caused by Coulomb blockade. It is interpreted as a phonon blockade [2] caused by coherent transfer of electronic energy to a quantized thickness vibration of the thin suspended cavity, in analogy to the Franck-Condon principle in molecular systems [3].

[1] A. D. V. Scheible, C. Weiss, J. P. Kotthaus, and R. H. Blick, Phys. Rev. Lett. 93, 186801 (2004)

[2] E. M. Weig, R. H. Blick, T. Brandes, J. Kirschbaum, W. Wegscheider, M. Bichler, and J. P. Kotthaus, Phys. Rev. Lett. 92, 046804 (2004)

[3] J. Koch and F. von Oppen, cond-mat/0409667