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Regensburg 2000 – scientific programme

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TT: Tiefe Temperaturen

TT 14: Wachstum und Transport in dünnen Filmen

TT 14.7: Talk

Wednesday, March 29, 2000, 16:15–16:30, H19

Surface resistances R(T ≤ 0.9 Tc, Hrf, f) of YBCO by weak links and indications for point defects — •Alexander Dierlamm, Ermile Gaganidze, and Juergen Halbritter — Forschungszentrum Karlsruhe, IMF 1, Postfach 3640, D-76021 Karlsruhe, Germany

YBa2Cu3O7−x contains nets of weak or strong links, point defects and other extrinsic and intrinsic reasons for rf residual losses. HTS-in-plane weak links show very much reduced jcJ(T) ≃ jcJ(0)(1−T/Tc)-values compared to theory and a large leakage current jbl of the order of jcJ ∝ 1/Rbl due to a high density of intermediate states in disordered HTS junction material. The finite residual losses Rres(T,Hrf,f) are due to the finite normal conducting leakage current of weak links with Rbl(T ≤ 0.9 Tc) ≃ const. in distances aJ. Quantitative agreement experiment - model in T and frequency dependence is obtained by measured values of aJ(≃ 0.2−20 µ m), of Rbn(≃ 1000 −1 nΩcm2) and of jcJ(≃ 102 − 107 A/cm2) with jcJRbl2 ≃ 5× 10−122 cm2. The observed scaling Rres(Hrf) ∝ 1/jcJ3/2(Hrf) indicates Josephson fluxon penetration in long weak links. The effect of point defect on T, Hrf and f dependence is discussed.

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