%0 Conference Paper
%A Schäfer, Christian
%A Teller, Justus
%A Bennemann, Benjamin
%A Moors, Kristof
%A Lyatti, Matvey
%A Lentz, Florian
%A Riwar, Roman
%A Schäpers, Thomas
%T Frustrated frustration and strong vortex pinning in Nb-Pt-Nb Josephson junction arrays
%M FZJ-2026-01369
%D 2025
%X Josephson junctions are among the most important devices in quantum computing, ranging from superconducting qubits to topological protection through Majorana fermions. They are often studied individually, but arranging them on a one- or two-dimensional grid to form a Josephson array allows to leverage collective phenomena. One proposed application is a topologically protected qubit [1]. When a magnetic field is applied in the out-of-plane direction, quantized circular supercurrents known as Josephson vortices appear. An integer or half-integer number of vortices per unit cell (plaquette) form a rigid lattice. Because vortex movement produces a voltage drop across the leads, the DC resistance dips at (half-)integer values of magnetic flux per unit cell, creating a "frustration pattern". A promising type of Josephson junction for Majorana physics is the multi-terminal Josephson junction, which has more than two superconducting electrodes. We study the frustration pattern of a square lattice with in-situ fabricated Nb-Pt-Nb four-terminal Josephson junctions (4TJJ) and compare it to arrays of conventionally fabricated two-terminal junctions (2TJJ) of different sizes. All arrays reproduce the well-studied frustration behavior. Additionally, the 2TJJ arrays exhibit a strongly pinned state at low temperatures. The magnetoresistance of the array is dominated by the Fraunhofer pattern of the individual junctions. The four-terminal geometry produces a checkerboard pattern of alternating fluxes f and f ′ piercing the plaquettes[2]. This type of frustrated frustration manifests as a beating pattern in the DC resistance. Consequently, 4TJJ arrays enable us to estimate the spatial extent of the central weak-link region. This region must be minimized for topological transitions to occur.[1] Ioffe et al., Nature 415, 503 (2002).[2] Teller et al., Arxiv 2503 14423 (2025)
%B Workshop on Innovative Nanoscale Devices and Systems
%C 7 Dec 2025 - 12 Dec 2025, Waikoloa (USA)
Y2 7 Dec 2025 - 12 Dec 2025
M2 Waikoloa, USA
%F PUB:(DE-HGF)6
%9 Conference Presentation
%U https://juser.fz-juelich.de/record/1053027