Creating Localized Majorana Zero Modes in Quantum Anomalous Hall Insulator/Superconductor Heterostructures with a Scissor

TL;DR

This paper proposes a novel method to create and manipulate Majorana zero modes in quantum anomalous Hall insulator/superconductor heterostructures by introducing a cut, enabling scalable topological quantum computing applications.

Contribution

The work introduces a practical approach to generate multiple Majorana zero modes using cuts in QAHI, avoiding the need for a large proximity gap and reducing in-gap state interference.

Findings

Creating a topologically protected helical channel with a cut in QAHI.

Inducing superconductivity on the helical channel yields MZMs at the ends.

Enables braiding of MZMs by controlling coupling between modes.

Abstract

In this work, we demonstrate that making a cut (a narrow vacuum regime) in the bulk of a quantum anomalous Hall insulator (QAHI) creates a topologically protected single helical channel with counter-propagating electron modes, and inducing superconductivity on the helical channel through proximity effect will create Majorana zero energy modes (MZMs) at the ends of the cut. In this geometry, there is no need for the proximity gap to overcome the bulk insulating gap of the QAHI to create MZMs as in the two-dimensional QAHI/superconductor (QAHI/SC) heterostructures. Therefore, the topological regime with MZMs is greatly enlarged. Furthermore, due to the presence of a single helical channel, the generation of low energy in-gap bound states caused by multiple conducting channels is avoided such that the MZMs can be well separated from other in-gap excitations in energy. This simple but practical approach allows the creation of a large number of MZMs in devices with complicated geometry such as hexons for measurement-based topological quantum computation. We further demonstrate how braiding of MZMs can be performed by controlling the coupling strength between the counter-propagating electron modes.