Regensburg 2000 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 17: Postersitzung II: Pinning und Vortexdynamik (1-8), Supraleitung: Theorie (9-13), Korrelierte Elektronen (14-48), Niederdimensionale Systeme (49-68), Quantenflüssigkeiten (69-75)

TT 17.60: Poster

Mittwoch, 29. März 2000, 14:30–18:00, A

Nanoscale Kondo Metal Point Contacts — •Jian Liu, Hartmut Buhmann und Laurens W Molenkamp — Physikalisches Institut, Universität Würzburg, Am Hubland, 97074 Würzburg

Metallic point contacts having a diameter down to some tens of nanometer have been fabricated in-house using a technology based on silicon nitride membranes, electron-beam lithography (EBL) and reactive ion etching (RIE). Point contacts fabricated from pure Au have been electrically characterised at liquid helium temperature. We use Wexlers’ equation to estimate the size of the point contacts from the low temperature contact resistance. The dc bias dependence of the differential conductance and its derivative (proportional to phonon scattering across the constriction) show a pronounced phonon-induced structure, indicating a good quality of the fabricated point contacts. In addition, Hall-bar-shaped samples of a Au:Fe spin-glass film (deposited by thermal evaporation) with different iron contents have been studied by measuring the Hall effect at 4.2K. The magnetic field dependence of the Hall-resistivity shows an additional non-linear component that is not present in pure Au films, and is a clear signature of the formation of a spin-glass. Combining the progress in lithography and spin-glass deposition, we intend to study the occurrence of possible size-effects on the Kondo temperature in sub-10nm point contacts in Kondo metals.