Quantum adiabatic transport in a quantum anomalous Hall insulator

An exceptional trait of the quantum Hall effect is quantum adiabatic transport, dissipationless quantized edge transport that is robust to bias voltages multiple orders of magnitude larger than any known relevant energy scale. This enables stable and highly sensitive measurements in quantum metrology at temperatures above 1 K. In contrast, prior experiments have shown that an electrical bias of the same order applied to the quantum anomalous Hall edge modes in magnetic topological insulators causes a breakdown of quantization, resulting from material limitations (electric field activates bulk transport). In this paper, to mitigate the effects of this electric field and study edge transport at a large electrical bias, we utilize electrochemical potential balancing. We find that electrical transport along the edge of a quantum anomalous Hall insulator is ubiquitously of dissipationless quantum adiabatic nature. In fact, we can verify that the adiabaticity holds at least up to an applied bias voltage of some 600 mV at 4.2 K, multiple orders of magnitude larger than any known energy scale associated with the quantum anomalous Hall state. This is a level of robustness on par with the conventional quantum Hall modes used in mainstream metrology.