Journal
PHYSICAL REVIEW B
Volume 105, Issue 20, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.105.L201405
Keywords
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Funding
- National Natural Science Foundation of China [12174095, 11804089, 12174096, 51772087, 11904094, 51972106]
- Natural Science Foundation of Hunan Province, China [2021JJ20026]
- Strategic Priority Research Program of Chinese Academy of Sciences [XDB30000000]
- Science and Technology Innovation Program of Hunan Province, China [2021RC3037]
- Natural Science Foundation of Chongqing, China [cstc2021jcyj-msxmX0381]
- Fundamental Research Funds for the Central Universities of China
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By studying the local electronic properties of magic-angle twisted bilayer graphene, we observe a breakdown of the flat bands at the sample terminated edge. We find that complete moiré spots are necessary for the generation of effective flat bands in twisted bilayer graphene.
Low-energy moir?? flat bands in magic-angle twisted bilayer graphene (tBG) have demonstrated incredible potential to exhibit rich exotic quantum phenomena. Theoretically, the moir?? flat bands of tBG are based on the extended structures, i.e., the moir?? patterns with periodic boundary conditions. However, a fundamental question of whether the flat bands can exist in the graphene moir?? patterns with a reduced structure symmetry, such as sample edges, remains unanswered. Here, via scanning tunneling microscopy and spectroscopy, we study the local electronic properties of magic-angle tBG near the sample terminated edge and report a direct observation of breakdown of the moir?? flat bands. We show that the moir?? electronic structures, including the low-energy flat bands, can sufficiently exist in a complete moir?? spot, i.e., a moir?? supercell, right at the edge even if the translational symmetry of the moir?? patterns is broken in one direction. However, the flat-band characteristic is obviously absent in the incomplete moir?? spots that are partly terminated by the edge. Our results indicate that a whole moir?? spot is sufficient and indispensable for the generation of the effective moir?? flat bands in tBG.
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