Quantum Percolation Effect in Quantum Anomalous Hall Insulators

The quantum anomalous Hall (QAH) effect is the zero magnetic field manifestation of the integer quantum Hall effect. In our recent experiments, we find that the magnetic TI sandwich devices show the perfect QAH state as long as the magnetic domain switching ratio is greater than the quantum percolation threshold of magnetic domains. To quantitively examine the quantum percolation effect on the chiral edge channels (CECs), we fabricate the QAH devices with a narrow constriction down to 50 nm. By performing magnetotransport measurements, we find that the magnetic transition peak near the coercive field is broadened when the width of the constriction is less than 300 nm. This observation suggests that the narrow constriction is more sensitive to magnetic domain switching. Moreover, our minor loop measurements show that the reversion of a single magnetic domain destroys the appearance of the dissipation-free CECs when the width of the constriction is less than 100nm. Our work paves the way for the potential applications of dissipationless CECs in energy-efficient electronics and spintronics, as well as topological quantum computations.