Chiral 1D transport in magnetic topological insulators: precise quantization and manipulation*

The quantum anomalous Hall effect in thin film magnetic topological insulators (MTIs) is characterized by chiral, one-dimensional conduction along the film edges when the sample is uniformly magnetized. This has been experimentally confirmed by measurements of quantized Hall resistance and near-vanishing longitudinal resistivity in magnetically doped (Bi,Sb)₂Te₃. I will describe two recent advances: 1. We have measured quantized Hall resistance in absence of an external magnetic field to precision and accuracy better than one part per million, and longitudinal resistivity below 10 mΩ, using techniques developed for quantum Hall metrology. We have also achieved some insight into the nature of residual dissipation. 2. Chiral conduction is expected not only along film edges but also along magnetic domain walls. Clear detection of these modes in MTIs has until recently proved challenging. We have intentionally created magnetic domain walls in an MTI, and study electrical transport along those domain walls. In agreement with theoretical predictions, we observe chiral transport along domain walls. I will also describe evidence that two modes equilibrate while co-propagating along the length of the domain wall.