Anomalous supercurrent from Majorana states in topological insulator Josephson junctions

We propose a Josephson junction setup based on a topological insulator (TI) thin film to detect Majorana states that exploits the unique helical and extended nature of the TI surface state. When the magnetic flux through the junction is close to an integer number of flux quanta, Majorana states, present on both surfaces of the film, give rise to a narrow peak-dip structure in the current-phase relation by hybridizing at the edge of the junction. Remarkably, the maximal Majorana-state contribution to Josephson current takes a (nearly) universal value, approximately equal to the supercurrent capacity of a single quantum channel. These features provide a characteristic signature of Majorana states based entirely on supercurrent.