Kavli Affiliate: Katja C. Nowack
| First 5 Authors: George M. Ferguson, Run Xiao, Anthony R. Richardella, Austin Kaczmarek, Nitin Samarth
| Summary:
The creation of topologically non-trivial 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 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.
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