Internal screening and dielectric engineering in magic-angle twisted bilayer graphene

Magic-angle twisted bilayer graphene (MA-tBLG) hosts intricate quantum many-body states. A critical contributor to these states are electron-electron interactions. What is the profile of the effective Coulomb interaction in MA-tBLG? And what determines this profile? Are intrinsic screening processes of MA-tBLG dominant or is the effective interaction mostly controlled by screening processes taking place in the surrounding dielectrics? Here, the authors show that the influence of the dielectric environment on the effective interaction depends decisively on the electronic state of MA-tBLG and propose experimental tailoring of the dielectric environment as a promising path towards resolving the nature of the quantum many-body states in MA-tBLG.