Fingerprint of chiral Majorana modes in resonant Andreev reflection at the edge of a quantum anomalous Hall insulator / superconductor heterostructure

With the recent discovery of the quantum anomalous Hall insulator (QAHI), which exhibits the conductive quantum Hall edge states without external magnetic field, it becomes possible to create a novel topological superconductor by introducing superconductivity into these edge states. In this case, two distinct topological superconducting phases with one or two chiral Majorana edge modes were theoretically predicted, characterized by Chern numbers ($N$) of 1 and 2, respectively. We present spectroscopic evidence from resonant Andreev reflection experiments for the presence of chiral Majorana modes in a Nb / (Cr$_{0.12}$Bi$_{0.26}$Sb$_{0.62}$)$_2$Te$_3$ heterostructure with unique signatures attributed to two different topological superconducting phases. The results are consistent with the theoretical predictions.