Regensburg 2022 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 26: Superconductivity: Tunnelling and Josephson Junctions
TT 26.14: Vortrag
Donnerstag, 8. September 2022, 13:00–13:15, H10
Josephson junctions with a metamaterial barrier — •Mikhail Belogolovskii1,2, Paul Seidel2, Ivan Nevirkovets3, and John Ketterson3 — 1Kyiv Academic University, Kyiv, Ukraine — 2Friedrich-Schiller-Universität, Jena, Germany — 3Northwestern University, Evanston, USA
Metamaterials represent a new class of synthetic media with a specific arrangement of constituent structural elements. Provided it occurs on scales smaller than characteristic lengths associated with the response to external factors, such approach makes it possible to reach novel properties not achieved in conventional materials. In our study dealing with complex Josephson junctions, we have analyzed how their supercurrent-vs-magnetic field dependencies are modified by a metamaterial barrier between superconductors (S) that is formed by ten bilayers of ultra-thin normal (N) and ferromagnetic (F) metals with a penetration depth of superconducting (S) correlations strongly exceeding their thicknesses. Instead of expected Fraunhofer patterns, in Josephson multilayers with S = Nb, N = Al, and F = Ni or Permalloy, we have observed periodic SQUID-like behavior. We argue theoretically that this effect emerges due to the interference of scattering amplitudes that suppresses quantum transport in the central part of the periodic weak link but leaves electron trajectories confined to its hinges. The proposed devices overcome the main obstacles on the way towards application of single Josephson junctions in nanoscale magnetometry since their critical current density is near the value of about 109 A/m2 required to overcome thermal fluctuations at several kelvins and the devices are intrinsically shunted. Moreover, such inherently stochastic junctions can be used for low-temperature probabilistic computing, an intermediate case between traditional deterministic electronics and emerging quantum computing. The work of Mikhail Belogolovskii was supported by the Volkswagen Stiftung grant 9B884.