Confinement-Induced Chiral Edge Channel Interaction in Quantum Anomalous Hall Insulators

• Published in: Physical review letters Vol. 130; no. 8; p. 086201
• Main Authors: Zhou, Ling-Jie, Mei, Ruobing, Zhao, Yi-Fan, Zhang, Ruoxi, Zhuo, Deyi, Yan, Zi-Jie, Yuan, Wei, Kayyalha, Morteza, Chan, Moses H W, Liu, Chao-Xing, Chang, Cui-Zu
• Format: Journal Article
• Language: English
• Published: United States 24.02.2023
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.130.086201

In quantum anomalous Hall (QAH) insulators, the interior is insulating but electrons can travel with zero resistance along one-dimensional (1D) conducting paths known as chiral edge channels (CECs). These CECs have been predicted to be confined to the 1D edges and exponentially decay in the two-dimensional (2D) bulk. In this Letter, we present the results of a systematic study of QAH devices fashioned in a Hall bar geometry of different widths under gate voltages. At the charge neutral point, the QAH effect persists in a Hall bar device with a width of only ∼72  nm, implying the intrinsic decaying length of CECs is less than ∼36  nm. In the electron-doped regime, we find that the Hall resistance deviates quickly from the quantized value when the sample width is less than 1  μm. Our theoretical calculations suggest that the wave function of CEC first decays exponentially and then shows a long tail due to disorder-induced bulk states. Therefore, the deviation from the quantized Hall resistance in narrow QAH samples originates from the interaction between two opposite CECs mediated by disorder-induced bulk states in QAH insulators, consistent with our experimental observations.