Observation of Integer and Fractional Chern insulators in high Chern number flatbands
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| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866915692009226240 |
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| author | Dong, Jingwei Liu, Le Zhu, Jundong Pan, Zitian Hong, Yu Wang, Fankun Ren, Zhiyuan Jia, Zhengnan Watanabe, Kenji Taniguchi, Takashi Du, Luojun Shi, Dongxia Yang, Wei Zhang, Guangyu |
| author_facet | Dong, Jingwei Liu, Le Zhu, Jundong Pan, Zitian Hong, Yu Wang, Fankun Ren, Zhiyuan Jia, Zhengnan Watanabe, Kenji Taniguchi, Takashi Du, Luojun Shi, Dongxia Yang, Wei Zhang, Guangyu |
| contents | Moiré flatbands with high Chern numbers (C>1) offer opportunities to study the fractional quantum anomalous Hall effects that go beyond the Landau level paradigm with C=1, which remain unexplored yet. Here, we target the novel topological phases in high Chern number flatbands by designing a new moiré system, i.e., twisted rhombohedral trilayer-bilayer graphene. We observe quantized anomalous Hall effects (QAH) with C = 3 at v = 1 and v = 3, demonstrating the high Chern number nature of the flat band from continuum calculations. By fractionally filling the flat band, we observe QAH with C = 2 at even-denominator fractional filling v = 3/2, as well as QAH with C = 3 continuously from v = 1 to the even-denominator v = 3/2 at zero magnetic fields. Most importantly, we observe, for the first time, evidence of an FCI with C = -6/5 at v = 12/5, corresponding to 2/5 filling of a high Chern number flat band with C = -3, verified by both Streda formula analysis and a fractionally QAH. It is also worth noting that Streda formula analysis reveals a signature of another FCI with C = -3/2 at v = 5/2 under finite magnetic fields. Our results demonstrate the tRTBG, which can be naturally extended to other twisted graphene moiré superlattices based on rhombohedral graphene multilayers, as a novel platform for hosting unconventional high Chern number correlated topology in the ultra-strong correlated regime that is beyond the paradigm of fractional phases with C < 1. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_09908 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Observation of Integer and Fractional Chern insulators in high Chern number flatbands Dong, Jingwei Liu, Le Zhu, Jundong Pan, Zitian Hong, Yu Wang, Fankun Ren, Zhiyuan Jia, Zhengnan Watanabe, Kenji Taniguchi, Takashi Du, Luojun Shi, Dongxia Yang, Wei Zhang, Guangyu Strongly Correlated Electrons Mesoscale and Nanoscale Physics Materials Science Moiré flatbands with high Chern numbers (C>1) offer opportunities to study the fractional quantum anomalous Hall effects that go beyond the Landau level paradigm with C=1, which remain unexplored yet. Here, we target the novel topological phases in high Chern number flatbands by designing a new moiré system, i.e., twisted rhombohedral trilayer-bilayer graphene. We observe quantized anomalous Hall effects (QAH) with C = 3 at v = 1 and v = 3, demonstrating the high Chern number nature of the flat band from continuum calculations. By fractionally filling the flat band, we observe QAH with C = 2 at even-denominator fractional filling v = 3/2, as well as QAH with C = 3 continuously from v = 1 to the even-denominator v = 3/2 at zero magnetic fields. Most importantly, we observe, for the first time, evidence of an FCI with C = -6/5 at v = 12/5, corresponding to 2/5 filling of a high Chern number flat band with C = -3, verified by both Streda formula analysis and a fractionally QAH. It is also worth noting that Streda formula analysis reveals a signature of another FCI with C = -3/2 at v = 5/2 under finite magnetic fields. Our results demonstrate the tRTBG, which can be naturally extended to other twisted graphene moiré superlattices based on rhombohedral graphene multilayers, as a novel platform for hosting unconventional high Chern number correlated topology in the ultra-strong correlated regime that is beyond the paradigm of fractional phases with C < 1. |
| title | Observation of Integer and Fractional Chern insulators in high Chern number flatbands |
| topic | Strongly Correlated Electrons Mesoscale and Nanoscale Physics Materials Science |
| url | https://arxiv.org/abs/2507.09908 |