Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 29: Superconductivity: Tunnelling, Josephson Junctions, SQUIDs 1
TT 29.5: Vortrag
Mittwoch, 28. März 2012, 16:00–16:15, H 2053
Subgap density of states in the superconductor Aluminum — •Andreas Heimes1, Michael Marthaler1, Juha Leppägankas2, Jens Michelsen1, and Gerd Schön1 — 1Institut für Theoretische Festkörperphysik and DFG-Center for Functional Nanostructures, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany — 2Department of Microtechnology and Nanoscience - MC2, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
In recent years great effort in screening envoironmental decoherence sources lead to an increased coherence time of Josephson based qubits. However there are still intrinsic mechanisms in the bulk superconductors that set a natural limit. According to that recent experiments measure a finite electronic density of states below the superconducting gap leading to incoherent quasiparticle tunneling. At the same time it was proposed that non-magnetic impurities at the superconductor-substrate interface or in the oxide tunneling barrier can cause magnetic impurities with a certain surface concentration which are believed amongst other to cause the 1/f flux noise. Here we propose that such surface spins could also be the reason for the observed subgap density of states in the phonon-mediated superconductor aluminum. We find that magnetic scattering in the bulk superconductor leads to a subgap tunneling rate that can be compared to the mentioned experimental observations.