Dresden 2003 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 6: Postersitzung I (Amorphe- u. Tunnelsysteme, Niedrigdimensionale Systeme, Supraleitung: Elektronenstruktur, Phononen, Tunneln, Ordnungsparameter)
TT 6.27: Poster
Montag, 24. März 2003, 14:30–19:00, P2c, P2d
Magnetotransport in Nb-InAs stripe arrays: proximity effect and edge channels — •J. Eroms1, D. Weiss1, J. De Boeck2, and G. Borghs2 — 1Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg — 2IMEC, Kapeldreef 75, B-3001 Leuven, Belgium
We have studied magnetotransport and differential current voltage characteristics of arrays of niobium stripes in contact with a 2DEG in a high-mobility InAs/AlGaSb heterostructure. At fields up to a few millitesla the stripes are Josephson-coupled and the array is superconducting. In an intermediate field range up to 200 mT the magnetotransport curves are strongly temperature dependent, which we ascribe to proximity induced superconductivity. At higher fields the magnetotransport curves taken at different temperatures lie on one of two branches, depending on whether the niobium stripes are superconducting or normal conducting. At high magnetic fields the longitudinal resistance in the superconducting state is higher than in the normal state. Therefore, the longitudinal resistance traces taken above Tc and below Tc intersect at a magnetic field position which depends on the spacing between the niobium stripes. This behaviour is only found in samples with a high transparency of the Nb-InAs contact. We assume that Andreev-reflected holes moving in the same direction as electrons at the sample edge reduce the conductivity of the edge channels and therefore the resistance is increased.