Coulomb drag in metallic twisted bilayer graphene

Strongly correlated phases in twisted bilayer graphene (TBG) typically arise as transitions from a state in which the system behaves as a normal metal. In such a metallic regime, electron-electron interactions usually only play a subleading role in transport measurements compared with the dominant scattering mechanism. Here, we propose and theoretically study an exception to this based on a Coulomb drag setup between two metallic TBGs separated so that they only couple through many-body interactions. We find that, by solely varying the twist angle equally in both TBGs, the drag resistivity exhibits a unique maximum as the system crosses over from a degenerate to a nondegenerate regime. When the twist angles in each TBG differ, we find an anomalous drag resistivity characterized by the appearance of multiple peaks. We show that this behavior can be related to the dependence of the rectification function on the twist angle. © 2023 American Physical Society.