Universal Conductance Fluctuations in Quantum Anomalous Hall Insulators

Universal conductance fluctuations (UCF) are a distinctive mesoscopic transport phenomenon that arises in disordered systems when the sample size approaches the phase coherence length of the system. As a hallmark of phase coherent transport, UCF shapes the low temperature transport properties of such systems in a fundamental way. In this study, UCF are reported in magnetically doped topological insulator thin films in the quantum anomalous Hall (QAH) regime. In mesoscopic QAH devices, aperiodic yet highly reproducible conductance fluctuations are observed, robust against variations in field sweeping direction and temperature. Two fluctuation components with distinct characteristic frequencies are revealed, and their contrasting temperature dependencies indicate that they originate from different interference processes associated with bulk and edge states, respectively. These finding uncovers rich quantum interference phenomena in the QAH insulators, providing new insights into mesoscopic transport in QAH systems.