Ferguson G M, Xiao Run, Richardella Anthony R, Low David, Samarth Nitin, Nowack Katja C
Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, NY, USA.
Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, USA.
Nat Mater. 2023 Sep;22(9):1100-1105. doi: 10.1038/s41563-023-01622-0. Epub 2023 Aug 3.
A quantum anomalous Hall (QAH) insulator is characterized by quantized Hall and vanishing longitudinal resistances at zero magnetic field that are protected against local perturbations and independent of sample details. This insensitivity makes the microscopic details of the local current distribution inaccessible to global transport measurements. Accordingly, the current distributions that give rise to transport quantization are unknown. Here we use magnetic imaging to directly visualize the transport current in the QAH regime. As we tune through the QAH plateau by electrostatic gating, we clearly identify a regime in which the sample transports current primarily in the bulk rather than along the edges. Furthermore, we image the local response of equilibrium magnetization to electrostatic gating. Combined, these measurements suggest that the current flows through incompressible regions whose spatial structure can change throughout the QAH regime. Identification of the appropriate microscopic picture of electronic transport in QAH insulators and other topologically non-trivial states of matter is a crucial step towards realizing their potential in next-generation quantum devices.
量子反常霍尔（QAH）绝缘体的特征在于，在零磁场下具有量子化的霍尔电阻和消失的纵向电阻，这些特性可抵御局部扰动且与样品细节无关。这种不敏感性使得局部电流分布的微观细节无法通过全局输运测量得知。因此，导致输运量子化的电流分布尚不清楚。在此，我们利用磁成像直接可视化QAH regime中的输运电流。当我们通过静电门控调节QAH平台时，我们清楚地识别出一个区域，在该区域中样品主要在体相中而非沿边缘传输电流。此外，我们对平衡磁化强度对静电门控的局部响应进行成像。综合这些测量结果表明，电流流经不可压缩区域，其空间结构在整个QAH regime中可能会发生变化。识别QAH绝缘体及其他拓扑非平凡物质状态中电子输运的合适微观图像，是实现其在下一代量子器件中潜力的关键一步。
