Observation of Chiral Transport along Magnetic Domain Walls in a Quantum Anomalous Hall Insulator*

The quantum anomalous Hall (QAH) effect, which has been realized in thin films of ferromagnetic topological insulators, features a single chiral edge mode that circles the boundary of the film, similarly to the ν=1 quantum Hall (QH) system. Unlike QH, the chirality of the QAH edge mode is determined by the film's magnetization, not by the external magnetic field. Magnetic domain walls in QAH insulators therefore form adjacent QAH systems of opposite chirality; dissipationless chiral conduction is expected along such magnetic domain walls[1,2]. Using Meissner screening to locally modulate the applied magnetic field, we intentionally form a magnetic domain wall in Cr-(Bi,Sb)₂Te₃[3]. We then use transport measurements to verify that conduction along magnetic domain walls is chiral and nearly dissipationless.

[1] R. Wakatsuki, M. Ezawa, and N. Nagaosa, Sci. Rep. 5, 13638 (2015).
[2] P. Upadhyaya and Y. Tserkovnyak, Phys. Rev. B 94, 020411 (2016).
[3] I. T. Rosen et al., Nat. Quantum Mater. (accepted, 2017), arXiv:1707.08677.