Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 33: Superconductivity: Vortex Physics

TT 33.5: Talk

Tuesday, April 1, 2014, 10:45–11:00, HSZ 201

Interference of edge and bulk pinning mechanisms in ultra-thin superconducting NbN and TaN mesoscopic bridges — •Konstantin Ilin and Michael Siegel — Iinstitute of Micro- and Nanoelectronic Systems, Karlsruhe Institute of Technology (KIT), Hertzstraße 16, 76187 Karlsruhe, Germany

Ultra-thin superconducting films are widely used for development of different types of radiation detectors. Usually, the operation conditions of the detectors are very close to the critical ones. Therefore the critical current density jc and its dependence on temperature and magnetic fields B are interesting not only from the fundamental point of view but very important for different applications. We present results on experimental investigations of jc(B) dependencies in thin film bridges made from NbN and TaN ultra-thin films deposited on sapphire substrates. We have found that in bridges with a width much smaller than the Pearl length and with a thickness about the coherence length (5 nm) the jc(B) dependence is non-monotonic. The critical current density oscillates at B = Bs corresponding to transition from the Meissner (B < Bs) to a vortex state. Moreover in the vortex state at B > Bs the jc(B) dependence is weaker than that one expected from the edge pinning mechanism solely. The observed phenomena could be explained by a significant contribution of a bulk pinning mechanism to the critical state of the current carrying superconducting mesoscopic structures.