Planar scanning gates for manipulating electronic interactions in van der Waals devices

Van der Waals (vdW) heterostructure devices have been shown to host a diverse range of electronic states that arise from the combination and rotational alignment of their component crystal flakes. For example, previous experiments on moire multilayer graphene devices with different gate dielectric thicknesses have suggested competition between superconducting and correlated insulating phases that can be tuned by Coulomb screening. However, the mechanisms that generate these behaviors remain controversial. Dynamic control of the Coulomb interaction strength in a local, uniform region of a vdW device can be a powerful tool for investigating emergent electronic states in 2D systems. We use a few-micron diameter graphite cylinder on the end of a scanning probe as a moveable electrostatic gate, which can be brought close to the surface of a vdW device, screening the Coulomb interactions in the nearest layers. We report on the progress of dynamic Coulomb screening experiments on moire graphene, and on opportunities for further development of this novel experimental system.