Twist-angle sensitivity of electron correlations in moiré graphene bilayers

摘要: Motivated by the recent observation of correlated insulator states and unconventional superconductivity in twisted bilayer graphene, we study dependence electron correlations on twist angle reveal existence strong over a narrow range angles near magic angle. Specifically, determine on-site extended Hubbard parameters low-energy Wannier using an atomistic quantum-mechanical approach. The ratio parameter width flat bands, which is indicator strength correlations, depends sensitively screening semiconducting substrate metallic gates. Including effect long-ranged Coulomb interactions significantly reduces explains experimentally observed sensitivity strong-correlation phenomena angles.