Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 8: Superconductivity - Poster Session

TT 8.30: Poster

Montag, 26. März 2007, 14:00–17:45, Poster A

0 and π phase Josephson coupling through an insulating barrier with magnetic impurities — •O. Vávra^1,2,3, Š. Gaži², I. Vávra², D. S. Goluboviś¹, J. Dérer², and V. V. Moshchalkov¹ — ¹Nanoscale Superconductivity and Magnetism Group, Laboratory for Solid State Physics and Magnetism, K. U. Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium — ²Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, SK-841 04 Bratislava, Slovak Republic — ³Institut für experimentelle und angewandte Physik, Universität Regensburg, D-93025 Regensburg, Germany

We present the experimental evidence of the existence of the π state in the Josephson junction with magnetic impurities in the insulating barrier. We have studied temperature and field dependencies of the critical current I_C in the Nb-Fe_0.1Si_0.9-Nb Josephson junction with tunneling barrier formed by paramagnetic insulator. We demonstrate that in these junctions the co-existence of both the 0 and the π states within one tunnel junction takes place which leads to the appearance of a sharp cusp in the temperature dependence I_C(T) similar to the I_C(T) cusp found for the 0−π transition in metallic π junctions. This cusp is not related to the 0−π temperature induced transition itself, but is caused by the different temperature dependencies of the opposing 0 and π supercurrents through the barrier.