Independently Tunable Flat Bands and Correlations in a Graphene Double Moiré

Novel double moiré system realized in a four-layer twist- controlled graphene structure

• Twisted bilayer graphene at magic angle hosts flat bands, correlated insulators and superconductivity
• Spatially separated flat bands can be realized in a twist-controlled four-layer graphene structure, where the twist between layers top two and bottom two layers is small, while the twist between layers 2 and 3 is intentionally kept large 
• Insulators observed when the Brillouin zones of individual top or bottom moiré are filled, provides evidence for spatially separated bands
• Individual moiré near magic angle show correlated insulators
• An electrostatic analysis of the resistance vs top and bottom gates provides the chemical potential vs filling factor of the flat bands