Signature of\nCorrelated Insulator in Electric Field\nControlled Superlattice

On a two-dimensional crystal, a “superlattice”\nwith\nnanometer-scale periodicity can be imposed to tune the Bloch electron\nspectrum, enabling novel physical properties inaccessible in the original\ncrystal. While creating 2D superlattices by means of nanopatterned\nelectric gates has been studied for band structure engineering in\nrecent years, evidence of electron correlationswhich drive\nmany problems at the forefront of physics researchremains\nto be uncovered. In this work, we demonstrate signatures of a correlated\ninsulator phase in Bernal-stacked bilayer graphene modulated by a\ngate-defined superlattice potential, manifested as resistance peaks\ncentered at integer multiples of single electron per superlattice\nunit cell carrier densities. The observation is consistent with the\nformation of a stack of flat low-energy bands due to the superlattice\npotential combined with inversion symmetry breaking. Our work paves\nthe way to custom-designed superlattices for studying band structure\nengineering and strongly correlated electrons in 2D materials.