Journal
NATURE
Volume 600, Issue 7889, Pages 439-+Publisher
NATURE PORTFOLIO
DOI: 10.1038/s41586-021-04002-3
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Funding
- US Department of Energy, Basic Energy Sciences Office, Division of Materials Sciences and Engineering [DE-SC0001819, DE-SC0019300]
- Gordon and Betty Moore Foundation [GBMF9468]
- ARO grant [W911NF-14-1-0247]
- National Science Foundation [DMR-1809802]
- STC Center for Integrated Quantum Materials (NSF grant) [DMR-1231319]
- Gordon and Betty Moore Foundation's EPiQS Initiative [GBMF9643, GBMF8683]
- Department of Defense through the National Defense Science and Engineering Graduate Fellowship Program
- Harvard Quantum Initiative in Science and Engineering
- Harvard Quantum Initiative Seed Fund
- Simons Investigator award
- Simons Collaboration on Ultra-Quantum Matter
- Simons Foundation [651440]
- Simons Investigator Fellowship
- NSF-DMR [1411343]
- German National Academy of Sciences Leopoldina through a Leopoldina fellowship [LPDS 2018-02]
- National Science Foundation Graduate Research Fellowship [DGE 1745303]
- Elemental Strategy Initiative by the MEXT, Japan [JPMXP0112101001]
- JSPS KAKENHI grant [JP20H00354]
- NSF [ECS-0335765]
- Direct For Mathematical & Physical Scien [1411343] Funding Source: National Science Foundation
- Division Of Materials Research [1411343] Funding Source: National Science Foundation
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Fractional Chern insulators (FCIs) are lattice analogues of fractional quantum Hall states and have been recently observed in magic-angle twisted BLG at low magnetic field. The appearance of these states at 5 T is accompanied by the disappearance of nearby topologically trivial charge density wave states.
Fractional Chern insulators (FCIs) are lattice analogues of fractional quantum Hall states that may provide a new avenue towards manipulating non-Abelian excitations. Early theoretical studies(1-7) have predicted their existence in systems with flat Chern bands and highlighted the critical role of a particular quantum geometry. However, FCI states have been observed only in Bernal-stacked bilayer graphene (BLG) aligned with hexagonal boron nitride (hBN)(8), in which a very large magnetic field is responsible for the existence of the Chern bands, precluding the realization of FCIs at zero field. By contrast, magic-angle twisted BLG(9-12) supports flat Chern bands at zero magnetic field(13-17), and therefore offers a promising route towards stabilizing zero-field FCIs. Here we report the observation of eight FCI states at low magnetic field in magic-angle twisted BLG enabled by high-resolution local compressibility measurements. The first of these states emerge at 5 T, and their appearance is accompanied by the simultaneous disappearance of nearby topologically trivial charge density wave states. We demonstrate that, unlike the case of the BLG/hBN platform, the principal role of the weak magnetic field is merely to redistribute the Berry curvature of the native Chern bands and thereby realize a quantum geometry favourable for the emergence of FCIs. Our findings strongly suggest that FCIs may be realized at zero magnetic field and pave the way for the exploration and manipulation of anyonic excitations in flat moire Chern bands.
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