▎ 摘　　要

We study the electronic structure of bilayer graphene flakes in which the constituent layers are mutually rotated by some angle theta. The large system sizes involved (up to 10(5) carbon atoms) necessitate the use of a tight-binding approach in conjunction with Lanczos diagonalization. We find that a single moire spot is sufficient for the low-energy density of states to resemble closely that of the periodic analog of such flakes, the graphene twist bilayer, implying that the low-energy physics in this system is well described as that of a "moire quantum well" trapping low-energy graphene electrons. Furthermore, a graphene twist flake consisting of a single moire unit cell leads already to electron localization on the AA "moire spot," in agreement with this moire quantum well picture. The electron density fluctuations induced by the moire lattice in twist graphene flakes are significant, being an order of magnitude greater than those generated by the rippling of suspended graphene. Finally, we determine the electronic properties of such flakes in the presence of an external magnetic field, finding a "zero-mode" structure and Landau states that exhibit an electron current well described as a charge flow on a torus situated at the AA regions of the moire lattice. DOI: 10.1103/PhysRevB.87.075433