Edge effects in the magnetic interference pattern of a ballistic SNS junction

Abstract

We investigate the Josephson critical current Ic(Φ) of a wide superconductor-normal metalsuperconductor (SNS) junction as a function of the magnetic flux Φ threading it. Electronic trajectories reflected from the side edges alter the function Ic(Φ) as compared to the conventional Fraunhofer-type dependence. At weak magnetic fields, B Φ0/d 2 , the edge effect lifts zeros in Ic(Φ) and gradually shifts the minima of that function toward half-integer multiples of the flux quantum. At B > Φ0/d 2 , the edge effect leads to an accelerated decay of the critical current Ic(Φ) with increasing Φ. At larger fields, eventually, the system is expected to cross into a regime of "classical" mesoscopic fluctuations that is specific for wide ballistic SNS junctions with rough edges.

Two-dimensional Josephson vortex lattice and anomalously slow decay of the Fraunhofer oscillations in a ballistic SNS junction with a warped Fermi surface

“…This accelerated decay is a known result [18]. What we have found here is that the switch from a circular to a square Fermi surface slows down the decay by a fourth root, from B −2 to B −1/2 .…”

“…11, the slow 1/ √ B decay persists even if the critical current is reduced substantially by the tunnel barrier. Disorder provides a stronger perturbation, in the form of random sample-specific fluctuations [18], but averaged over series of peaks the slow decay persists.…”

Crossed Andreev reflection in InSb flake Josephson junctions

“…Such a supercurrent offset cannot be due to a partial short in the JJ, since we confirmed the supercurrent can be pinched off by the global bottom gate [21]. Because of its insensitivity to magnetic field, the offset cannot stem from mechanisms that occur at a certain magnetic field either [30,31].…”

Tailoring supercurrent confinement in graphene bilayer weak links

“…The transition from a beating pattern (Fraunhofer-like) to a monotonically decaying pattern is visible confirming the continuous change in the supercurrent confinement from 2D to 1D. The coloured dashed lines correspond to the split-gate values where the dV /dI(VSG, B) maps were measured in panels a.field B (see supplementary information for details), using a quasi-classical approach (as in [44,51,52]) with an additional input given by the presence of a QPC-like structure in the middle of the device (see the geometry used in Fig. 5a).…”