A novel technique to extract features of flat bands in a moiré Superlattice

Abstract: Twisted multilayer graphene systems with nearly flat bands are ideal platforms for studying strongly correlated physics. Exotic phases of matter such as correlated insulators at integer fillings, superconductivity, and anomalous quantum hall have been observed in such systems. However, a straightforward technique to directly extract detailed flat band features is still lacking. We propose a novel technique for the study of flat bands using a decoupled monolayer graphene on a magic-angle twisted monolayer bilayer graphene heterostructure. We not only extract the width of the flat bands by measuring the chemical potentials, but also directly map the evolution of the electron-electron correlation as a function of the external displacement field. Through our measurements, we observe that the correlation maximizes where the flat band width is minimum. This new device configuration with an additional decoupled monolayer graphene can pave a way to study the flat bands which can further improve the understanding of the electronic band structure.