Noise signatures for determining chiral Majorana fermion modes

TL;DR

This paper investigates how noise measurements can differentiate between chiral Majorana fermion modes and disorder-induced metallic phases in quantum anomalous Hall insulator-superconductor systems, providing a method to identify the true origin of conductance plateaus.

Contribution

It introduces a noise-based diagnostic approach to distinguish chiral Majorana modes from disorder effects in transport measurements.

Findings

Current noise signatures differ between Majorana modes and metallic phases.

Noise measurement can identify the mechanism without additional fabrication.

Local current density distributions are distinct for the two mechanisms.

Abstract

The conductance measurement of a half quantized plateau in a quantum anomalous Hall insulator-superconductor structure is reported by a recent experiment [Q. L. He \textit{et al.}, Science 357, 294-299 (2017)], which suggests the existence of the chiral Majorana fermion modes. However, such half quantized conductance plateau may also originates from a disorder-induced metallic phase. To identify the exact mechanism, we study the transport properties of such a system in the presence of strong disorders. Our results show that the local current density distributions of these two mechanisms are different. In particular, the current noises measurement can be used to distinguish them without any further fabrication of current experimental setup.