Layer-Resolved Microwave Imaging of a van der Waals Heterostructure.

van der Waals heterostructures host a wide range of strongly correlated states, but the imaging of quantum phenomena in three-dimensional heterostructures is challenging because multiple layers may contribute to the detected signal. Here we introduce an imaging technique that resolves electronic states on individual atomic planes of a heterostructure, layer by layer, down to milli-Kelvin temperatures. We demonstrate layer-resolved microwave impedance microscopy of quantum Hall states in double-layer graphene, achieved by precisely modulating the vertical transmission of microwaves into the heterostructure. By visualizing charge fluctuations on individual planes, we shed light on the roles of surface disorder and screening on the stability of fractional quantum Hall states, while extracting key properties such as gap sizes and negative compressibility. This approach is also compatible with microscopy with displacement field control, unlocking access to exotic quantum phenomena that can only be realized in multilayer structures and top-gated devices.