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TT: Fachverband Tiefe Temperaturen

TT 48: Superconductivity: Heterostructures, Andreev Scattering, Proximity Effect, Vortices

TT 48.8: Talk

Friday, March 30, 2012, 11:30–11:45, H 2053

Characterization and electronic transport properties of nanostructured Pb/Fe point contacts — •Jörg Gramich¹, Gernot Goll¹, Christoph Sürgers², and Hilbert v. Löhneysen^1,2 — ¹DFG-Centrum für Funktionelle Nanostrukturen, KIT Karlsruhe — ²Physikalisches Institut, KIT Karlsruhe

We experimentally investigate the spin-polarized transport through nanostructured Pb/Fe point contacts at low temperatures. All samples are produced by in-situ evaporation of the metals on either side of a Si₃N₄ membrane with a nanostructured hole, resulting in clean metal interfaces. A direct measurement of the nanocontact size allows for the first time a comparison with theoretical models for contact-size estimates of heterocontacts. The ballistic transport regime for contacts with high Knudsen ratio is demonstrated by features in the spectra such as phonon peaks and the critical pair-breaking current of Pb. The spin polarization P of the current through the superconductor-ferromagnet contact is determined by means of Andreev reflection at the S/F interface. The observed systematic dependence on the contact radius a and superconducting transition temperature T_c is compared to previous measurements on Al/Fe nanocontacts.