Spectroscopic Fingerprint of Chiral Majorana Modes at the Edge of a Quantum Anomalous Hall Insulator / Superconductor Heterostructure

TL;DR

This paper reports spectroscopic evidence of chiral Majorana modes in a heterostructure combining a quantum anomalous Hall insulator with a superconductor, confirming theoretical predictions of topological superconducting phases.

Contribution

The study provides experimental spectroscopic evidence for chiral Majorana modes in a QAHI/superconductor heterostructure, supporting the existence of distinct topological superconducting phases.

Findings

Spectroscopic signatures consistent with chiral Majorana modes.

Observation of two different topological superconducting phases.

Qualitative agreement with theoretical predictions.

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 novel topological superconductor (SC) 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 Andreev reflection experiments for the presence of chiral Majorana modes in a Nb / (Cr0.12Bi0.26Sb0.62)2Te3 heterostructure with distinct signatures attributed to two different topological superconducting phases. The results are in qualitatively good agreement with the theoretical predictions.