Regensburg 2022 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 3: Superconductivity: Properties and Electronic Structure
TT 3.2: Vortrag
Montag, 5. September 2022, 09:45–10:00, H23
High-precision impedance measurements near the Berezinski-Kosterlitz-Thouless transition in strongly disordered superconductors — •Lea Pfaffinger1, Alexander Weitzel1, Thomas Huber1, Klaus Kronfeldner1, Lorenz Fuchs1, Sven Linzen2, Evgeni Il’ichev2, Nicola Paradiso1, and Christoph Strunk1 — 1University of Regensburg, Germany — 2Leibniz Institute of Photonic Technology, Jena, Germany
We investigate the Berezinskii-Kosterlitz-Thouless (BKT) transition - a vortex induced topological phase transition - in 3 nm thin atomically layer deposited NbN films. The samples are placed inside a RLC-resonator, whose design enables us to perform AC measurements of the superfluid stiffness Js and four-probe current-voltage (IV) characteristics in the same cooling cycle. In contrast to earlier experiments, we observe a sharp discontinuous jump of Js at the BKT transition temperature TBKT. Comparison of the Js and the DC resistance measurements reveal quantitative agreement of both TBKT and Tc0. Powerlaw exponents extracted of IV characteristics agree quantitatively with Js and calculations based on renormalization group. Surprisingly, if a DC current is added to the rf-drive, Js(I) reaches a pronounced maximum before dropping sharply to zero at a current much smaller than the pair breaking critical current. This behaviour may be tentatively explained as a cut-off of the BKT renormalisation flow by the current.