Measured Potential Profile in a Quantum Anomalous Hall System SuggestsBulk-Dominated Current Flow br

Ideally, quantum anomalous Hall systems should display zero longitudinal resistance. Yet inexperimental quantum anomalous Hall systems elevated temperature can make the longitudinal resistancefinite, indicating dissipative flow of electrons. Here, we show that the measured potentials at multiplelocations within a device at elevated temperature are well described by solution of Laplace's equation,assuming spatially uniform conductivity, suggesting nonequilibrium current flows through the two-dimensional bulk. Extrapolation suggests that at even lower temperatures current may still flow primarilythrough the bulk rather than, as had been assumed, through edge modes. An argument for bulk current flowpreviously applied to quantum Hall systems supports this picture