THz sensing of band selective quantum compressibility in vdW heterostructures

Semimetals are defined by multiple electron and hole pockets on the Fermi surface, which can each exhibit a distinct effective mass and scattering rate. Determining the role of collective properties and strong interactions that may manifest more in one band than another can be challenging, as the responses of multiple pockets are mixed together in the linear DC conductivity. Here, we measure the THz conductivity of a heterostructure consisting of a graphene monolayer and a few-nanometer thick graphite gate layer using on-chip THz spectroscopy. We find that the symmetric plasmon mode of the bilayer structure is sensitive to the hole pocket in graphite. We develop a model that can be used to probe the band-selective quantum compressibility, and discuss what this can reveal in correlated multi-band semimetals.