Direct visualization of electronic transport in a quantum anomalous Hall insulator

Area of Science:

• Condensed Matter Physics
• Quantum Materials Science

Background:

• Quantum anomalous Hall (QAH) insulators exhibit quantized Hall resistance and zero longitudinal resistance without an external magnetic field.
• These properties are robust against local perturbations, making microscopic current distribution details elusive through traditional transport measurements.

Purpose of the Study:

• To directly visualize the local current distribution within a QAH insulator.
• To understand the spatial characteristics of current flow and its relation to electronic transport in the QAH regime.

Main Methods:

• Utilized advanced magnetic imaging techniques to directly observe current flow.
• Employed electrostatic gating to tune the system through different QAH plateaus.
• Correlated magnetic imaging with local magnetization measurements.

Main Results:

• Directly visualized the transport current in the QAH regime.
• Identified a distinct regime where current predominantly flows through the bulk, not just the edges.
• Observed that the spatial structure of incompressible regions, carrying the current, changes with electrostatic gating.

Conclusions:

• The study reveals that current in QAH insulators can flow through the bulk, challenging previous assumptions.
• The findings highlight the dynamic nature of current distribution and incompressible regions within the QAH regime.
• This work is essential for a deeper understanding of topologically non-trivial states and their application in quantum devices.