Spectroscopic fingerprint of chiral Majorana modes at the edge of a quantum anomalous Hall insulator/superconductor heterostructure.

Shen, Junying; Lyu, Jian; Gao, Jason Z; Xie, Ying-Ming; Chen, Chui-Zhen; Cho, Chang-Woo; Atanov, Omargeldi; Chen, Zhijie et al. · Proc Natl Acad Sci U S A · 2020

basic_science · Level V

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Abstract

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 topological superconductor (SC) by introducing superconductivity into these edge states. In this case, 2 distinct topological superconducting phases with 1 or 2 chiral Majorana edge modes were theoretically predicted, characterized by Chern numbers (N) of 1 and 2, respectively. We present spectroscopic evidence from Andreev reflection experiments for the presence of chiral Majorana modes in an Nb/(Cr<sub>0.12</sub>Bi<sub>0.26</sub>Sb<sub>0.62</sub>)<sub>2</sub>Te<sub>3</sub> heterostructure with distinct signatures attributed to 2 different topological superconducting phases. The results are in qualitatively good agreement with the theoretical predictions.