Jürgen Kötzler

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By means of the linear dynamic conductivity, inductively measured on epitaxial films between 30mHz and 30 MHz, the transition line Tg(B) to generic superconductivity is studied in fields between B=0 and 19T. It follows closely the melting line Tm(B) described recently in terms of a blowout of thermal vortex loops in clean materials. The critical exponents(More)
The linear conductance G' + iG(") parallel to the CuO(2) planes of flat d = 50-600 nm thin films is measured between 30 mHz and 800 kHz. The decay of the phase-coherent superfluid density signals the proliferation of 3D vortex loops which terminates at T*<T(c), where omegaG"(T*) attains 35(5) nH(-1) being independent of d. We ascribe this novel transition(More)
Above the upper critical field we have investigated the field dependences of the surface conductance, G'-iG" and the critical current J(c) of an electropolished pure niobium cylinder. The low frequency limits of G', G", and J(c) display power-law singularities, defining a transition to coherent surface superconductivity at H(c)(c3). The critical exponents(More)
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