Superconducting interference in a one dimensional system

Semiconducting nanowires coupled to superconductors are crucial in proposals for inducing, detecting and controlling topological superconductivity and Majorana fermion bound states. Using NbTiN-InSb-NbTiN Josephson junctions, we study supercurrents flowing in quasi-ballistic nanowires with strong spin-orbit interaction and in high magnetic fields, thus combining the essential ingredients required for Majorana fermions. Without taking particular care of the chemical potential in the nanowire, we observe supercurrent oscillations at finite magnetic field. Having ruled out a conventional Fraunhofer effect, we analyze these oscillations in terms of supercurrents modified by Zeeman splitting, spin-orbit interaction and orbital interference effects. We find orbital interference to dominate over other mechanisms. Demonstrating and controlling orbital interference effects is crucial to understand the signatures of Majorana fermions in Josephson junctions and it will inform the future construction of topological quantum circuits.

This research constitutes a continuing project from his PhD research at the QuTech institute, Delft University of Technology