Gate-defined bilayer graphene superlattices

Periodic potentials overlaid on crystal lattices lead to ‘superlattices’, that significantly modify the electronic phases of materials. Creating such potential landscapes on length scales much larger than the lattice constant can lead to the formation of minibands at low energies. In graphene-based moiré systems, such superlattices are created by rotating two similar layers or by aligning layers with slightly varying lattice constants. In such moiré systems, the Coulomb potential acts over the superlattice period, leading to flat bands and strongly correlated physics. However, challenges such as twist angle inhomogeneity, strain, and disorder can degrade device quality, making the observations of strongly correlated phases challenging. To address these limitations, alternative approaches such as periodic dielectric patterning and proximity of another moiré lattice near the graphene layer have been explored in recent years. In this work, we investigate Bernal-stacked bilayer graphene under a patterned graphite gate with a period of approximately 50 nm. Upon applying a superlattice gate voltage, we observe new insulating states. Further investigations of their magnetic field and temperature dependence reveal details about the Fermi surface topology and activated energy gaps. These insulating states, absent in regular Bernal bilayer graphene, demonstrate that the artificial superlattice modulates the band structure of bilayer graphene, leading to the emergence of new electronic phases.