Magnetic field- and electro-chemical potential- driven 0-pi transitions in an InSb-Al nanowire Josephson junction

Recent developments in shadow-wall lithography techniques yield hybrid nanowire Josephson junctions with magnetic field-resilient supercurrent that can be embedded in more complex hybrid devices to study supercurrent phenomena in high magnetic fields.  We fabricate a superconducting quantum interference device (SQUID) with two InSb-Al nanowire Josephson junctions as two arms in the dc-SQUID architecture. Local bottom gates are used to fix and sweep the electro-chemical potential of the junctions used as the reference and investigated arm, respectively. We perform switching current measurements and detect SQUID oscillations at parallel magnetic fields up to ~0.75T. The oscillation patterns measured while sweeping the gate of the investigated arm reveal multiple pi-shifted segments at high field which gate range gradually extends as the field increases. Some of these pi-segments are present at zero field as well and can be attributed to presence of an accidental quantum dot – as confirmed by tunnel spectroscopy. Other pi-segments can be tracked to oscillation patterns of various shapes at zero field. In order to understand these various evolutions, we develop a model for transport through a quantum dot coupled to a transmission channel in a hybrid Josephson junction.