Multiple Andreev reflections in topological Josephson junctions with chiral Majorana modes

Official URL: https://dx.doi.org/10.1103/PhysRevB.107.184510

Andreev bound states (ABSs) occur in Josephson junctions when the total phase of the Andreev and normal reflections is a multiple of 2π. In ballistic junctions with an applied voltage bias, a quasiparticle undergoes multiple Andreev reflections before entering the leads, resulting in peaks in the current-voltage I(V) curve. Here we present a model for a two-dimensional S/TI/MTI/TI/S junction, where S is a superconductor, TI is a topological insulator, and MTI is a magnetic topological insulator barrier. We show that the interplay of broken time-reversal symmetry and topology results in an asymmetric I(V) curve. Such junctions are predicted to host chiral Majorana modes. We demonstrate that the peak positions in I(V) are directly linked to ABSs. We use this to show how the angle-resolved I(V) curve becomes a spectroscopic tool for the chirality and degeneracy of ABSs.