Anomalous Josephson Current In Superconductor/Topological Insulator Devices

Josephson junctions (JJs) with topological insulator weak links are expected to host low-energy Andreev bound states (ABSs) giving rise to a current-phase relation that sharply deviates from a conventional sinusoidal behavior. Of particular interest are zero-energy Majorana bound states that form either at a vortex or when a phase difference of π is imposed between the two closely-spaced superconducting leads of the junction. In this talk, I will present signatures of an anomalous supercurrent carried by topologically non-trivial ABSs in various superconducting quantum interference devices (SQUIDs) made of Nb/Bi2Se3/Nb junctions. An electrostatic top gate placed on the JJs allows strong modulation of the Josephson current and the realization of a topological phase transition. I will discuss the possible mechanisms including the presence of a Majorana mode which could lead to qualitative modifications in the SQUID oscillations and single-junction diffraction patterns.