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ST494 - Internally Shunted Josephson Junctions: a Unified Analysis

Internally Shunted Josephson Junctions: a Unified Analysis

Vincenzo Lacquaniti1, Cristina Cassiago1, Natascia De Leo1, Matteo Fretto1, Andrea Sosso1, Pascal Febvre2, Volodymyr Shaternik3, Andrii Shapovalov3, Olexandr Suvorov3, Mikhail Belogolovskii3, Paul Seidel4
1INRIM; National Institute for Metrological Research, Strada delle Cacce 91, 10135 Torino, Italy
2Université Savoie Mont Blanc, Campus Scientifique, 73376 Le Bourget du Lac cedex, France
3Department of Superconducting Electronics, G.V. Kurdyumov Institute for Metal Physics, 03680 Kyiv, Ukraine
4Low Temperature Group, Friedrich-Schiller-Universität Jena, Germany
Abstract — Following the ever-rising demand for new functionalities and novel materials in superconducting circuitry, we provide a complete view on the self-shunting problem in Josephson junctions relating it to specific features of a multichannel weak link between electrodes where averaging over the channels yields a bimodal distribution of transparencies with maxima near unity and zero. We provide two examples of such internally-shunted devices, four-layered Nb/Al-Al oxide-Nb junctions with strongly disordered nm-thick insulating layers where stochastic distribution of transparencies takes place on a local rather than a global scale and MoRe/W-doped Si-Si–MoRe devices with strongly inhomogeneous silicon interlayers partly doped by metallic nanoclusters where the main charge transport occurs across resonance-percolating trajectories. We show how the predicted universal distribution function of transmission coefficients can be verified experimentally without any fitting parameters and analyze some old and new experimental data from this perspective. We believe that our results can form a base for novel four-layered Josephson junctions with enhanced superconducting properties and, at the same time, well-separated metallic electrodes.
Keywords (Index Terms) — Josephson junctions, current-voltage characteristics, tunneling, charge carrier processes, distribution functions.
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), January 2016. 
Submitted November 12, 2015; Selected November 16, 2015. Reference No. ST494; Category 4.
EUCAS 2015 preprint 2A-E-O1.6. Submitted to IEEE Trans. Appl. Supercond. for possible publication.