Tuning Coulomb interactions in moiré graphene with planar scanning probes

Moiré van der Waals heterostructure devices have demonstrated a wide array of emergent quantum electronic phases, including unconventional superconductivity and correlated insulators in magic angle twisted bilayer graphene and related graphitic systems. Coulomb interactions have been shown to play a role in the formation or suppression of these states. However, previous experiments exploring Coulomb screening by measuring devices with different gate dielectric thicknesses have been limited by the inherent variability between devices of the twist angle and other disorder sources. Dynamic control of the Coulomb interaction strength in a local device region, where the twist angle remains relatively constant, has yet to be demonstrated. Using a scanning probe terminated by a few-micron diameter metallic plane parallel to a moiré heterostructure, we can determine the twist angle in a local region, then increase the screening of Coulomb interactions in that region by lowering the probe toward the device. We report on the operation of this novel experimental system and preliminary results on how emergent electronic states in 2D heterostructures are affected by changes in electron-electron interactions.