Direct visualization of electronic transport in a quantum anomalous Hall insulator

Kavli Affiliate: Katja C. Nowack

| First 5 Authors: G. M. Ferguson, Run Xiao, Anthony R. Richardella, David Low, Nitin Samarth

| Summary:

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 the 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 the
magnetization to electrostatic gating. Combined, these measurements suggest
that incompressible regions carry the current within the QAH regime. Our
observations indicate that the self-consistent electrostatics of the sample
play a central role in determining the current distribution. Identifying 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.

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