Mesoscopic Transport Behaviors in Miniaturized Quantum Anomalous Hall devices*

The quantum anomalous Hall (QAH) systems are considered an important candidate for quantum device applications because they offer lossless current-carrying capability in absence of an external magnetic field. However, a comprehensive understanding of mesoscopic transport in sub-micron size regime QAH has yet been established, which is crucial for designing and modeling miniaturized QAH devices. Here, the QAH effects are successfully demonstrated in narrow Hall-bar devices with channel width down to 600 nm. Through measurement of size-dependent breakdown current, we confirm that the chiral edge states in QAH are confined at the physical boundary of the QAH mesa with its width on the order of Fermi wavelength. The narrow channel provides an additional back-scattering path through percolative hopping between local compressible puddles. The information on domain dynamics and phase coherent length is obtained through analysis of large resistance fluctuations, which is associated with collective interference between intersecting paths along domain walls. Our work suggests the QAH edge states are mesoscopically different from quantum Hall edge states and are fundamentally more robust against device scaling.