Visualizing the breakdown of the quantum anomalous Hall effect

• 成果类型: Article
• 署名作者: Ferguson, G. M.; Xiao, Run; Richardella, Anthony R.; Kaczmarek, Austin; Samarth, Nitin; Nowack, Katja C.
• 署名单位: Cornell University; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; Cornell University; Max Planck Society
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2515400123
• 发表日期: 2026-03-10
• 页码: 2515400123
• 关键词: topological phases of matter; quantum anomalous Hall effect; condensed matter physics; magnetic imaging; SPIN-ORBIT TORQUE; thermal-conductivity; DISSIPATION; relaxation; SCATTERING; electrons; emission

摘要

The creation of topologically nontrivial matter across electronic, mechanical, cold-atom, and photonic platforms is advancing rapidly, yet understanding the breakdown of topological protection remains a major challenge. In this work, we use magnetic imaging combined with global electrical transport measurements to visualize the current-induced breakdown of the quantum anomalous Hall effect (QAHE) in a magnetically doped topological insulator. We find that dissipation emerges at localized hot spots near electrical contacts, where an abrupt change in Hall angle leads to significant distortions of the current density. Using changes in the local magnetization as a proxy for electron temperature, we directly observe that the electrons are driven out of equilibrium with the lattice at the hot spots and throughout the device in the breakdown regime. By characterizing energy relaxation processes in our device, we show that the breakdown of quantization is governed entirely by electron heating, and that a vanishing thermal relaxation strength at millikelvin temperatures limits the robustness of the QAHE. Our findings provide a framework for diagnosing energy relaxation in topological materials and will guide realizing robust topological protection in magnetic topological insulators.