Electronic Reconstruction at the Quasicrystal-Moir\'e Crossover in Twisted Bilayer Graphene

Abstract

Large twist angles in twisted bilayer graphene are widely expected to be electronically trivial, with negligible interlayer coupling and no electronic reconstruction, in contrast to the rich moir\'e-driven band reconstruction and correlated physics that emerge at small twist angles. Here, we show that this paradigm breaks down near a twist angle of 29{\deg}, where the system crosses over between quasicrystalline and commensurate order. Atomic-resolution transmission electron microscopy directly reveals the coexistence of near-dodecagonal quasicrystalline symmetry and emerging moir\'e periodicity, indicating an intermediate, nonperiodic structural regime. Magnetotransport measurements uncover strong interlayer hybridization mediated by Umklapp scattering, manifested by magneto-intersubband oscillations and a highly unconventional Landau-level spectrum. Remarkably, the Landau-level degeneracy evolves from 4- to 12-fold with increasing temperature, a behavior incompatible with two decoupled graphene monolayers. These findings establish large-angle twisted bilayer graphene as a platform where quasiperiodic symmetry fundamentally reshapes low-energy electronic states beyond the conventional moir\'e framework.