Exploring Current Flow Using Cryogenic Scanning Magnetometry based on NV Centers in Diamond

Magnetic topological insulators are known to exhibit quantum anomalous Hall effect, which has an insulating bulk and quantized edge channels. However, examination of the spatial structure of the edge current as well as its dissipationless nature is still lacking in detail. Here, we introduce a home-built cryogenic diamond nitrogen-vacancy (NV) scanning system with a broad range of working temperatures as a way to explore the details of the dissipationless edge current and the underlying interactions in the system. Our measurement apparatus allows local measurements of magnetic fields with a sensitivity of a few nT/Hz^1/2 and spatial resolution of about 100 nm which are ideally suitable for the study.