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TT: Tiefe Temperaturen

TT 6: Postersitzung I: Josephsonkontakte und SQUIDs, Supraleitung: Theorie, Korrelierte Elektronen, Niederdimensionale Systeme, Magnetotransport, Quantenhalleffekt, Kohlenstoff-Nanoröhrchen, Quantenflüssigkeiten

TT 6.59: Poster

Montag, 26. März 2001, 14:30–17:00, Rang S\ 3

dc–Electron Transport on Thin Helium Films: IV–Characteristics and Mobility for Different Substrates — •Irena Doicescu, Jürgen Klier,, and Paul Leiderer — Fakultät für Physik, Universität Konstanz, Postfach 5560 M676, D-78457 Konstanz

Electrons above a liquid helium surface exist as a 2–dimensional (2D) layer of charges. If the underlying substrate is an arrangement of in-plane metal electrodes held at ascending potentials, then the electrons move along the x–direction above the helium film. With our configuration of source, split-gate, and drain electrodes (plus an additional pick-up-electrode where the electrons are directly measured), we realize a 2D charge transport in analogy to a FET [1]. The measured dc–current depends on the applied voltage of the split-gate. A negative gate voltage confines the electrons laterally to a narrow channel, so the reduced effective width of the channel leads to a quasi one-dimensional charge transport. The IV–characteristics measured for a metal and a silicon substrate are compared and discussed. The electron current strongly depends on the thickness of the helium film, because the roughness of the substrate plays an important role in case of a thin film. By analyzing the electron current we can conclude about the density and mobility of the electrons. Based on these results we present new theoretical approach and experimental evidence to the so-called dip-problem of the electron current, hence the mobility, on a thin helium film on different substrates.

[1] J. Klier, I. Doicescu, P. Leiderer, J. Low Temp. Phys. 121, (2000).