Anomalous Fraunhofer interference in epitaxial superconductor-semiconductor Josephson junctions

Abstract

Fraunhofer interference is a paradigmatic phenomena arising due to phase coherence in diverse systems from optics to superconducting junctions. In Josephson junctions, coupling two superconductors through a weak link, such patterns arise in the maximal dissipationless current the system can sustain, oscillating as function of a perpendicular applied magnetic field. By investigating this effect in a recently realized material system epitaxially coupling a thin superconductor to a semiconducting region, the authors here discover novel effects arising due to a combination of magnetic field screening, spin physics, and disorder. In an appropriately aligned in-plane magnetic field, they find that due to screening by the superconducting leads, a flux dipole develops in the semiconducting region leading to an effective confinement of the superconducting states to edges of the intervening semiconducting region. When the out-of-plane field is swept in the presence of an in-plane field, striking asymmetries in the Fraunhofer pattern are observed. By analyzing the underlying theoretical symmetries of the system, they demonstrate that such an effect arises as a result of an intricate interplay between disorder in the junction, splitting of the spin states in the applied field, and coupling between the momentum of the electrons and their spin.