Kavli Affiliate: Katja C. Nowack
| First 5 Authors: G. M. Ferguson, Run Xiao, Anthony R. Richardella, Austin Kaczmarek, Nitin Samarth
| Summary:
Magnetic topological insulators (MTIs) host topologically protected edge
states, but the role that these edge states play in electronic transport
remains unclear. Using scanning superconducting quantum interference device
(SQUID) microscopy, we performed local measurements of the current distribution
in a quantum anomalous Hall (QAH) insulator at large bias currents, where the
quantization of the conductivity tensor breaks down. We find that bulk currents
in the channel interior coexist with edge currents at the sample boundary.
While the position of the edge current changes with the reversal of the
magnetic field, it does not depend on the current direction. To understand our
observations, we introduce a model which includes contributions from both the
sample magnetization and currents driven by chemical potential gradients. To
parameterize our model, we use local measurements of the chemical potential
induced changes in the sample magnetization. Our model reveals that the
observed edge currents can be understood as changes in the magnetization
generated by the electrochemical potential distribution in the sample under
bias. Our work underscores the complexity of electronic transport in MTIs and
highlights both the value and challenges of using magnetic imaging to
disentangle various contributions to the electronic transport signatures.
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