Signatures of Majorana States in the Current-Phase Relation of Lateral S-TI-S Josephson Junctions

Superconductor-Topological Insulator-Superconductor (S-TI-S) lateral Josephson junctions are explored as a platform for topologically-protected Majorana-based quantum computing. In the S-TI-S junction barrier, Majorana bound states (MBS) are nucleated at the cores of Josephson vortices where the local phase difference is an odd multiple of π. Due to the presence of MBS, the current-phase relation of an S-TI-S junction is modified to include a 4π-periodic contribution. We describe and present results from two experiments designed to measure the current-phase relation directly via phase-sensitive Josephson interferometry in two regimes. The first uses a SQUID interferometer circuit that allows measurement of the CPR in the absence of an applied magnetic field and is sensitive to extended Majorana states in the junction. The second uses transport measurements of the magnetic field dependence of the critical current in asymmetric SQUIDs that yields the CPR of the smaller junction and is sensitive to localized Majorana states.