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Peer-reviewedCC BYProceedings of the National Academy of Sciences of the United States of America

Extended fractional Hofstadter states at high field in twisted bilayer graphene above the magic angle.

  • Joe Finney1,2
  • Aaron Sharpe1,2
  • Linsey K Rodenbach1,2
  • Jian Kang3
  • Xiaoyu Wang4
  • Kenji Watanabe5
  • Takashi Taniguchi6
  • Marc A Kastner1,2,7
  • Oskar Vafek4,8
  • David Goldhaber-Gordon1,2
8 affiliations
  1. 1Department of Physics, Stanford University, Stanford, CA 94305.
  2. 2Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025.
  3. 3School of Physical Science and Technology, ShanghaiTech University, Shanghai 200031, China.
  4. 4National High Magnetic Field Laboratory, Tallahassee, FL 32310.
  5. 5Research Center for Functional Materials, National Institute for Materials Science, Tsukuba 305-0044, Japan.
  6. 6International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan.
  7. 7Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139.
  8. 8Department of Physics, Florida State University, Tallahassee, FL 32306.
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Abstract

When a Chern band is partially filled, a fractional Chern insulator (FCI)-the lattice analog of a fractional quantum Hall state-can arise. Though the full range of possible scenarios for producing such a state is not established, the most tractable models combine strong electronic interactions with the quantum geometry of the parent Chern band meeting specific criteria. In twisted bilayer graphene, the importance of interactions can be tuned by varying the interlayer twist. Here, we study a sample with twist near 1.4°, large enough to suppress the zero-field correlated states. We find that applying a strong magnetic field restores the importance of electron-electron interactions: at nearly half a magnetic flux quantum per moiré unit cell, deep in the Hofstadter regime, odd-denominator fractional states appear in multiple Hofstadter subbands. These fractional states persist over larger ranges of density, and are more robustly quantized, than nearby integer states, opposite to what is seen in other fractional quantum Hall and FCI systems.

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Cite

BibTeXRIS
BibTeX
@article{finney2026extended,
  title = {{Extended fractional Hofstadter states at high field in twisted bilayer graphene above the magic angle.}},
  author = {Joe Finney and Aaron Sharpe and Linsey K Rodenbach and Jian Kang and Xiaoyu Wang and Kenji Watanabe and Takashi Taniguchi and Marc A Kastner and Oskar Vafek and David Goldhaber-Gordon},
  journal = {Proceedings of the National Academy of Sciences of the United States of America},
  year = {2026},
  month = oct,
  doi = {10.1073/pnas.2602080123},
  url = {https://europepmc.org/article/MED/42832671},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - Extended fractional Hofstadter states at high field in twisted bilayer graphene above the magic angle.
AU  - Joe Finney
AU  - Aaron Sharpe
AU  - Linsey K Rodenbach
AU  - Jian Kang
AU  - Xiaoyu Wang
AU  - Kenji Watanabe
AU  - Takashi Taniguchi
AU  - Marc A Kastner
AU  - Oskar Vafek
AU  - David Goldhaber-Gordon
PY  - 2026
DA  - 2026/10/05
JO  - Proceedings of the National Academy of Sciences of the United States of America
DO  - 10.1073/pnas.2602080123
UR  - https://europepmc.org/article/MED/42832671
AB  - When a Chern band is partially filled, a fractional Chern insulator (FCI)-the lattice analog of a fractional quantum Hall state-can arise. Though the full range of possible scenarios for producing such a state is not established, the most tractable models combine strong electronic interactions with the quantum geometry of the parent Chern band meeting specific criteria. In twisted bilayer graphene, the importance of interactions can be tuned by varying the interlayer twist. Here, we study a sample with twist near 1.4°, large enough to suppress the zero-field correlated states. We find that applying a strong magnetic field restores the importance of electron-electron interactions: at nearly half a magnetic flux quantum per moiré unit cell, deep in the Hofstadter regime, odd-denominator fractional states appear in multiple Hofstadter subbands. These fractional states persist over larger ranges of density, and are more robustly quantized, than nearby integer states, opposite to what is seen in other fractional quantum Hall and FCI systems.
SN  - 0027-8424
SN  - 1091-6490
ER  -