Robust Majorana bound states in magnetic topological insulator nanoribbons with fragile chiral edge channels

TL;DR

This paper investigates magnetic topological insulator nanoribbons with superconducting coverage, demonstrating that Majorana bound states are more robust to disorder than the fragile chiral edge channels, advancing potential quantum computing applications.

Contribution

It provides a comparative analysis of the robustness of Majorana bound states versus chiral edge channels against disorder in magnetic topological insulator nanoribbons.

Findings

Majorana bound states are more resilient to disorder than chiral edge channels.

Disorder significantly affects the ballistic nature of chiral edge channels.

Superconducting coverage enhances the stability of Majorana states.

Abstract

Magnetic topological insulators in the quantum anomalous Hall regime host ballistic chiral edge channels. When proximitized by an $s$-wave superconductor, these edge states offer the potential for realizing topological superconductivity and Majorana bound states without the detrimental effect of large externally-applied magnetic fields on superconductivity. Realizing well-separated unpaired Majorana bound states requires magnetic topological insulator ribbons with a width of the order of the transverse extent of the edge state, however, which is expected to bring the required ribbon width down to around 100 nm. In this regime, it is known to be extremely difficult to retain the ballistic nature of chiral edge channels and realize a quantized Hall conductance. In this paper, we study the impact of disorder in such magnetic topological insulator nanoribbons and compare the fragility of ballistic chiral edge channels with the stability of Majorana bound states when the ribbon is covered by a superconducting film. We find that the Majorana bound states exhibit greater robustness against disorder than the underlying chiral edge channels.