Moiré Band Topology in Twisted Bilayer Graphene
| Autor: | Takashi Taniguchi, Chao Ma, Shaofan Yuan, Scott Mills, Cheng Li, Xiaolong Chen, Fan Zhang, Bingchen Deng, Fengnian Xia, Kenji Watanabe, Qiyue Wang, Xu Du |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Condensed Matter - Materials Science
Materials science Condensed Matter - Mesoscale and Nanoscale Physics Condensed Matter - Superconductivity Mechanical Engineering Flatness (systems theory) Bioengineering 02 engineering and technology General Chemistry Moiré pattern 021001 nanoscience & nanotechnology Condensed Matter Physics Topology Condensed Matter - Strongly Correlated Electrons General Materials Science 0210 nano-technology Bilayer graphene Topology (chemistry) |
| Zdroj: | Nano Letters. 20:6076-6083 |
| ISSN: | 1530-6992 1530-6984 |
| Popis: | Recently twisted bilayer graphene (t-BLG) emerges as a new strongly correlated physical platform near a magic twist angle, which hosts many exciting phenomena such as the Mott-like insulating phases, unconventional superconducting behavior and emergent ferromagnetism. Besides the apparent significance of band flatness, band topology may be another critical element in determining strongly correlated twistronics yet receives much less attention. Here we report compelling evidence for nontrivial noninteracting band topology of t-BLG moir\'e Dirac bands through a systematic nonlocal transport study, in conjunction with an examination rooted in $K$-theory. The moir\'e band topology of t-BLG manifests itself as two pronounced nonlocal responses in the electron and hole superlattice gaps. We further show that the nonlocal responses are robust to the interlayer electric field, twist angle, and edge termination, exhibiting a universal scaling law. While an unusual symmetry of t-BLG trivializes Berry curvature, we elucidate that two $Z_2$ invariants characterize the topology of the moir\'e Dirac bands, validating the topological edge origin of the observed nonlocal responses. Our findings not only provide a new perspective for understanding the emerging strongly correlated phenomena in twisted van der Waals heterostructures, but also suggest a potential strategy to achieve topologically nontrivial metamaterials from topologically trivial quantum materials based on twist engineering. Comment: 26 pages, 4 figures, and 1 table |
| Databáze: | OpenAIRE |
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