Tuning Chern Number in Quantum Anomalous Hall Insulators

TL;DR

This paper reports the fabrication of magnetic topological insulator multilayers with tunable Chern numbers up to 5, advancing control over quantum anomalous Hall states for potential electronic and quantum computing applications.

Contribution

It introduces a method to tune the Chern number in QAH insulators via magnetic doping and layer thickness, supported by a theoretical phase diagram.

Findings

Achieved QAH effect with Chern number up to 5.

Demonstrated tuning of Chern number by doping and layer thickness.

Developed a theoretical model explaining the experimental phase diagram.

Abstract

The quantum anomalous Hall (QAH) state is a two-dimensional topological insulating state that has quantized Hall resistance of h/Ce2 and vanishing longitudinal resistance under zero magnetic field, where C is called the Chern number. The QAH effect has been realized in magnetic topological insulators (TIs) and magic-angle twisted bilayer graphene. Despite considerable experimental efforts, the zero magnetic field QAH effect has so far been realized only for C = 1. Here we used molecular beam epitaxy to fabricate magnetic TI multilayers and realized the QAH effect with tunable Chern number C up to 5. The Chern number of these QAH insulators is tuned by varying the magnetic doping concentration or the thickness of the interior magnetic TI layers in the multilayer samples. A theoretical model is developed to understand our experimental observations and establish phase diagrams for QAH insulators with tunable Chern numbers. The realization of QAH insulators with high tunable Chern numbers facilitates the potential applications of dissipationless chiral edge currents in energy-efficient electronic devices and opens opportunities for developing multi-channel quantum computing and higher-capacity chiral circuit interconnects.