Magnetic field dependence of the critical current in YBa2Cu3O7−δ/Au/Nb ramp-zigzag Josephson junctions

Abstract

We study the critical current Ic dependence on applied magnetic field H for multifacet YBa2Cu3O7−δ/Au/Nb ramp-type zigzag Josephson junctions. For many experiments, one would like to apply a homogeneous field in the junction plane. However, even tiny misalignments can cause drastic deviations from homogeneity. We show this explicitly by measuring and analyzing Ic versus H for an eight-facet junction, forming an array of 4×(0−π) segments. The ramp angle is θr=8∘. H is applied under different angles θ relative to the substrate plane and different angles φ relative to the in-plane orientation of the zigzags. We find that a homogeneous flux distribution is only achieved for an angle θh≈1∘–2∘ and that even a small misalignment ∼0.1∘ relative to θh can cause a substantial inhomogeneity of the flux density inside the junction, drastically altering its Ic versus H interference pattern. We also show that there is a dead angle θd* relative to θh of similar magnitude, where the average flux density completely vanishes.

Source-reported materials — not catalogue approval

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