Experimental signatures of Majorana bound states in S-TI-S lateral Josephson junctions

We present experiments designed to search for features of Majorana bound states (MBS) in lateral Josephson junctions formed by depositing s-wave superconductors onto the surface of topological insulator thin films. In a vertical magnetic field that induces a phase gradient across the junction, the localized MBS are expected to be stable at the cores of Josephson vortices where the phase difference across the junction is an odd multiple of π. To test this picture, we have fabricated Nb-Bi₂Se₃-Nb Josephson junctions with different geometries and carried out extensive measurements of their Josephson supercurrent vs. magnetic field diffraction patterns and the statistical critical current switching distribution in hysteretic junctions. Our results show a number of expected features of MBS, including: (1) finite critical current at the location of odd-numbered nodes of the diffraction pattern, (2) anomalous critical current distributions characterized by either a double peak in the switching distribution or an increase in the standard deviation of the distribution changes at values of magnetic field at which MBS are expected to be present in the junction. We will present a compilation of our data and analysis of these experiments.