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Twisted bilayer graphene exhibits a panoply of many-body phenomena that are intimately tied to the appearance of narrow and well isolated electronic bands near magic-angle. The microscopic ingredients that are responsible for the complex experimental phenomenology include electron-electron (phonon) interactions and non-trivial Bloch wavefunctions associated with the narrow bands. Inspired by recent experiments, we focus here on an interplay of two independent interaction-induced phenomena on superconductivity. We analyze the combined effects of Coulomb interaction driven band-flattening and phonon-mediated attraction due to the exchange of multiple electron-phonon umklapp processes, as a function of filling and twist angle. The former leads to a filling-dependent enhancement of the renormalized density of states, which contributes to a robust increase in the tendency towards pairing in a range of angles near magic-angle. In addition, the minimal spatial extent associated with the Wannier functions develops a non-trivial enhancement as a result of these many-body renormalizations, which can further contribute towards stabilizing the superconducting state over a wider range of fillings and twist-angles.
We present a simple model that we believe captures the key aspects of the competition between superconducting and insulating states in twisted bilayer graphene. Within this model, the superconducting phase is primary, and arises at generic fillings,
Recently twisted bilayer graphene (t-BLG) emerges as a new strongly correlated physical platform near a magic twist angle, which hosts many exciting phenomena such as the Mott-like insulating phases, unconventional superconducting behavior and emerge
Recent experiments have observed possible spin- and valley-polarized insulators and spin-triplet superconductivity in twisted double bilayer graphene, a moire structure consisting of a pair of Bernal-stacked bilayer graphene. Besides the continuously
We introduce and analyze a model that sheds light on the interplay between correlated insulating states, superconductivity, and flavor-symmetry breaking in magic angle twisted bilayer graphene. Using a variational mean-field theory, we determine the
We calculate the interactions between the Wannier functions of the 8-orbital model for twisted bilayer graphene (TBG). In this model, two orbitals per valley centered at the AA regions, the AA-p orbitals, account for the most part of the spectral wei