Charge smoothening and band flattening due to Hartree corrections in twisted bilayer graphene

Abstract

Doping twisted bilayer graphene away from charge neutrality leads to an enormous buildup of charge inhomogeneities within each moir\'e unit cell. Here, we show, using unbiased real-space self-consistent Hartree calculations on a relaxed lattice, that Coulomb interactions smoothen this charge imbalance by changing the occupation of earlier identified ``ring'' orbitals in the AB/BA region and ``center'' orbitals at the AA region. For hole doping, this implies an increase of the energy of the states at the $\mathrm{\ensuremath{\Gamma}}$ point, leading to a further flattening of the flat bands and a pinning of the Van Hove singularity at the Fermi level. The charge smoothening will affect the subtle competition between different possible correlated phases.