Direct observation of moiré flat-band breakdown at the edge of magic-angle twisted bilayer graphene

Low-energy moir\'e flat bands in magic-angle twisted bilayer graphene (tBG) have demonstrated incredible potential to exhibit rich exotic quantum phenomena. Theoretically, the of tBG are based on extended structures, i.e., patterns with periodic boundary conditions. However, a fundamental question whether can exist reduced structure symmetry, such as sample edges, remains unanswered. Here, via scanning tunneling microscopy and spectroscopy, we study local electronic properties near terminated edge report direct observation breakdown bands. We show that including low-energy bands, sufficiently complete spot, supercell, right at even if translational symmetry is broken one direction. flat-band characteristic obviously absent incomplete spots partly by edge. Our results indicate whole spot sufficient indispensable for generation effective tBG.