Unconventional Josephson Signatures of Majorana Bound States

A junction between two topological superconductors containing a pair of Majorana fermions exhibits a fractional Josephson effect, 4 pi periodic in the superconductors' phase difference. An additional fractional Josephson effect, however, arises when the Majorana fermions are spatially separated by a superconducting barrier. This new term gives rise to a set of Shapiro steps which are essentially absent without Majorana modes and therefore provides a unique signature for these exotic states.