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Title: Observation of 0–π transition in SIsFS Josephson junctions

The 0–π transition in Superconductor-Insulator-superconductor-Ferromagnet-Superconductor (SIsFS) Josephson junctions (JJs) was investigated experimentally. As predicted by theory, an s-layer inserted into a ferromagnetic SIFS junction can enhance the critical current density up to the value of an SIS tunnel junction. We fabricated Nb′ | AlO{sub x} | Nb | Ni{sub 60}Cu{sub 40} | Nb JJs with wedge-like s (Nb) and F (Ni{sub 60}Cu{sub 40}) layers and studied the Josephson effect as a function of the s- and F-layer thickness, d{sub s} and d{sub F}, respectively. For d{sub s} = 11 nm, π-JJs with SIFS-type j{sub c}(d{sub F}) and critical current densities up to j{sub c}{sup π}=60 A/cm{sup 2} were obtained at 4.2 K. Thicker d{sub s} led to a drastic increase of the critical current decay length, accompanied by the unexpected disappearance of the 0–π transition dip in the j{sub c}(d{sub F}) dependence. Our results are relevant for superconducting memories, rapid single flux quantum logic circuits, and solid state qubits.
Authors:
; ;  [1] ; ; ; ; ;  [2]
  1. Nanoelektronik, Technische Fakultät, Christian-Albrechts-Universität zu Kiel, Kaiserstr. 2, 24143 Kiel (Germany)
  2. Physikalisches Institut and Center for Collective Quantum Phenomena in LISA"+, Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen (Germany)
Publication Date:
OSTI Identifier:
22399118
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 2; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRITICAL CURRENT; CURRENT DENSITY; ELECTRIC CONTACTS; FERROMAGNETIC MATERIALS; FERROMAGNETISM; JOSEPHSON EFFECT; JOSEPHSON JUNCTIONS; LAYERS; LOGIC CIRCUITS; QUBITS; SEMICONDUCTOR JUNCTIONS; SOLIDS; SUPERCONDUCTORS; TUNNEL EFFECT