Tuning Coulomb interactions in moiré van der Waals systems with planar scanning probes

In van der Waals materials, the moiré pattern formed by introducing a twist angle or lattice constant mismatch between two crystalline layers can generate superconductivity and other correlated electronic phases. Recent experiments have suggested that the superconductivity in magic-angle twisted bilayer graphene (MATBG) competes with nearby correlated insulating states and may have unconventional origins, but the exact mechanisms that yield the rich phase diagram of MATBG are yet to be understood. Several prior studies have attempted to uncover the effect of Coulomb interactions on the emergence of correlated states in MATBG by incorporating a tunable dielectric or metallic layer in close proximity to the moire system. Our work uses a scanning probe tip terminated in a device-scale, ultra-flat graphite disk to dynamically influence electronic interactions in a moiré graphene device. By strongly damping tip-sample vibrations within our dilution refrigerator, we can position a probe within a few nanometers of the device surface, screening Coulomb interactions in the graphene layers. We report on the progress toward dynamic Coulomb screening measurements on moiré graphene, and on the potential for further scientific advancements using this novel scanning probe measurement system.