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【Abstract】

The unexpected discovery of superconductivity and strong electron correlation in twisted bilayer graphene, a system composed solely of s-p electrons, stands as one of the most intriguing developments in two-dimensional materials in recent years. A key feature of this system is the emergence of flat energy bands near the Fermi level (a condition that promotes the formation of novel many-body phases) at the so-called “magic angles”. Gaining a deeper understanding of the physical origin of these flat bands is essential for constructing an effective theory of unconventional electron correlation. In this talk, I will present our recent theory on the origin of these magic angles in twisted graphene layers and their connection to the Fermi ring in AA-stacked multilayer graphene.