Tuning the Chern number in quantum anomalous Hall insulators

Yi-Fan Zhao, Ruoxi Zhang, Ruobing Mei, Ling-Jie Zhou, Hemian Yi, Ya-Qi Zhang, Jiabin Yu, Run Xiao, Ke Wang, Nitin Samarth, Moses H. W. Chan, Chao-Xing Liu () and Cui-Zu Chang ()
Additional contact information
Yi-Fan Zhao: The Pennsylvania State University
Ruoxi Zhang: The Pennsylvania State University
Ruobing Mei: The Pennsylvania State University
Ling-Jie Zhou: The Pennsylvania State University
Hemian Yi: The Pennsylvania State University
Ya-Qi Zhang: The Pennsylvania State University
Jiabin Yu: The Pennsylvania State University
Run Xiao: The Pennsylvania State University
Ke Wang: The Pennsylvania State University
Nitin Samarth: The Pennsylvania State University
Moses H. W. Chan: The Pennsylvania State University
Chao-Xing Liu: The Pennsylvania State University
Cui-Zu Chang: The Pennsylvania State University

Nature, 2020, vol. 588, issue 7838, 419-423

Abstract: Abstract A quantum anomalous Hall (QAH) state is a two-dimensional topological insulating state that has a quantized Hall resistance of h/(Ce2) and vanishing longitudinal resistance under zero magnetic field (where h is the Planck constant, e is the elementary charge, and the Chern number C is an integer)1,2. The QAH effect has been realized in magnetic topological insulators3–9 and magic-angle twisted bilayer graphene10,11. However, the QAH effect at zero magnetic field has so far been realized only for C = 1. Here we realize a well quantized QAH effect with tunable Chern number (up to C = 5) in multilayer structures consisting of alternating magnetic and undoped topological insulator layers, fabricated using molecular beam epitaxy. The Chern number of these QAH insulators is determined by the number of undoped topological insulator layers in the multilayer structure. Moreover, we demonstrate that the Chern number of a given multilayer structure can be tuned by varying either the magnetic doping concentration in the magnetic topological insulator layers or the thickness of the interior magnetic topological insulator layer. We develop a theoretical model to explain our experimental observations and establish phase diagrams for QAH insulators with high, tunable Chern number. The realization of such insulators facilitates the application of dissipationless chiral edge currents in energy-efficient electronic devices, and opens up opportunities for developing multi-channel quantum computing and higher-capacity chiral circuit interconnects.

Date: 2020
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DOI: 10.1038/s41586-020-3020-3

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