SKM 2021 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 1: Focus Session: Disordered and Granular Superconductors: Fundamentals and Applications in Quantum Technology I
TT 1.8: Vortrag
Montag, 27. September 2021, 12:30–12:45, H6
Current-enhanced superfluid stiffness near the Berezinskii-Kosterlitz-Thouless transition in strongly disordered NbN-films — •Alexander Weitzel1, Lea Pfaffinger1, Klaus Kronfeldner1, Thomas Huber1, Lorenz Fuchs1, Sven Linzen2, Evgenii Il’ichev2, Nicola Paradiso1, and Christoph Strunk1 — 1Experimental and Applied Physics, Uni Regensburg, Germany — 2Leibniz Institute of Photonic Technology, Jena, Germany
We investigate resistivity and kinetic inductance in long and ultra-thin NbN strips near the superconductor-insulator transition. Resistive transition is dominated by superconducting fluctuations of both amplitude and phase of the order parameter. Near the foot of the transition, the resistivity displays a square-root cusp divergence of the conductance expected for the Berezinski-Kosterlitz-Thouless (BKT) transition. The superfluid stiffness of the very same strip (measured using an RLC-resonator technique) displays a sharp drop close to the universal value of 2TBKT/π. Current voltage (IV) characteristics become non-linear below Tc, with a complex back-bending shape that signals a heating instability. At lower temperatures, IV-characteristics feature a peculiar negative curvature in a log-log representation. This indicates a reduction of dissipation with respect to the standard power-law behavior of the IV-characteristics and is corroborated by the observation of an unexpected increase of kinetic inductance near the critical current.