Title: Incommensurate transitions and twist disorder in microscopic models of twisted bilayer graphene
Abstract: Recent experiments in twisted bilayer graphene have set off a flurry of work due to the observation of purportedly correlated phases at the so-called “magic-angle.” However, the current models in the literature for magic-angle graphene suffer from two flaws: they assume commensurate twist angles and have great difficulty modeling the exact experimental setup where patches of different twist angles appear (“twist disorder”). We introduce and study a family of microscopic models that begins to address these concerns. In these models, the twist angle enters as a free parameter in real space. We can use this to simulate both incommensurate effects and disorder effects. We find that incommensuration leads to an Anderson-like delocalization transition in momentum space. The result is a small metallic phase at the “magic-angle” (that we speculate is unstable to correlated phases). We further study twist-disorder effects and find that while the minibandwidth is renormalized substantially, the Fermi velocity is not significantly altered.
Host: Jen Cano