Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 26: Superconductivity: Vortex Dynamics, Vortex Phases, Pinning
TT 26.4: Vortrag
Mittwoch, 27. Februar 2008, 16:30–16:45, H 3010
Self-generated vortices in NbN ultra-thin film structures — •Konstantin Ilin1, Michael Siegel1, Andreas Engel2, Holger Bartolf2, Andreas Schilling2, Alexei Semenov3, and Heinz-Wilhelm Huebers3 — 1Institute of Micro- and Nano-Electronic Systems, University of Karlsruhe, Germany — 2Physics Institute, University of Zurich, Switzerland — 3DLR e.V. Institute of Planetary Research, Berlin, Germany
Detectors of electro-magnetic radiation made from NbN ultra-thin superconducting films find their application in different fields: astronomy, optical and THz spectroscopy, imaging and security. The detecting element of these devices is typically a micrometer or sub-micrometer wide superconducting strip operating at temperatures well below the critical temperature. The bias current required for proper operation of detectors is about the critical value. We present results on study of a current-generated critical state in 3-5 nm thick NbN structures with different width. The critical current of micrometer wide strips of ultra-thin NbN film is almost independent of temperature below 6 K. This is typically caused by de-pinning of self-generated magnetic vortices in current carrying superconductors. A reduction of the strip width leads to an increase of the critical current density approaching the value of de-pairing critical current for 300-400 nm wide stripes, which are much larger than the coherence length in NbN films. We describe the obtained results in term of the three-current model considering an enhancement of the Bean-Livingston edge barrier for vortex penetration with decreasing width of superconducting strip.