Flat bands through electrically tunable superlattice in Bernal stacked bilayer graphene

In 2-dimensional (2d) crystals, imposing nanometer-scale periodicity allows tuning the fundamental Bloch electron spectrum, enabling novel physics properties which are not accessible in the original crystal. A celebrated example is the Moire heterostructures where wide variety of exotic charge transport phenomena emerges. In recently years, a top-down approach for creating 2d superlattice on monolayer graphene by meaning of nanopatterning of electric gate has been studied, allowing formation of custom-design superlattice potential and study of band structure engineering. With this approach, however, electron correlation which leads to many forefront physics problems, remains to be undiscovered. Here we discuss our work on Bernal-stacked bilayer graphene modulated by gate-defined superlattice potential. We observed strong evidence of formation flat band stacks which potentially host correlated electrons. We will also discuss possible signatures of correlated insulator in these systems. The possibility to induce correlated electrons with nanopatterning defined electric gates paves the path to custom-design superlattices with arbitrary geometries and symmetries, for studying band structure engineering and strongly correlated electrons in 2d materials.