Observation of fractionally quantized anomalous Hall effect

Heonjoon Park, Jiaqi Cai, Eric Anderson, Yinong Zhang, Jiayi Zhu, Xiaoyu Liu, Chong Wang, William Holtzmann, Chaowei Hu, Zhaoyu Liu, Takashi Taniguchi, Kenji Watanabe, Jiun-Haw Chu, Ting Cao, Liang Fu, Wang Yao, Cui-Zu Chang, David Cobden, Di Xiao and Xiaodong Xu ()
Additional contact information
Heonjoon Park: University of Washington
Jiaqi Cai: University of Washington
Eric Anderson: University of Washington
Yinong Zhang: University of Washington
Jiayi Zhu: University of Washington
Xiaoyu Liu: University of Washington
Chong Wang: University of Washington
William Holtzmann: University of Washington
Chaowei Hu: University of Washington
Zhaoyu Liu: University of Washington
Takashi Taniguchi: National Institute for Materials Science
Kenji Watanabe: National Institute for Materials Science
Jiun-Haw Chu: University of Washington
Ting Cao: University of Washington
Liang Fu: Massachusetts Institute of Technology
Wang Yao: University of Hong Kong
Cui-Zu Chang: The Pennsylvania State University
David Cobden: University of Washington
Di Xiao: University of Washington
Xiaodong Xu: University of Washington

Nature, 2023, vol. 622, issue 7981, 74-79

Abstract: Abstract The integer quantum anomalous Hall (QAH) effect is a lattice analogue of the quantum Hall effect at zero magnetic field1–3. This phenomenon occurs in systems with topologically non-trivial bands and spontaneous time-reversal symmetry breaking. Discovery of its fractional counterpart in the presence of strong electron correlations, that is, the fractional QAH effect4–7, would open a new chapter in condensed matter physics. Here we report the direct observation of both integer and fractional QAH effects in electrical measurements on twisted bilayer MoTe2. At zero magnetic field, near filling factor ν = −1 (one hole per moiré unit cell), we see an integer QAH plateau in the Hall resistance Rxy quantized to h/e2 ± 0.1%, whereas the longitudinal resistance Rxx vanishes. Remarkably, at ν = −2/3 and −3/5, we see plateau features in Rxy at $$\frac{3}{2}h/{e}^{2}\pm 1 \% $$ 3 2 h / e 2 ± 1 % and $$\frac{5}{3}h/{e}^{2}\pm 3 \% $$ 5 3 h / e 2 ± 3 % , respectively, whereas Rxx remains small. All features shift linearly versus applied magnetic field with slopes matching the corresponding Chern numbers −1, −2/3 and −3/5, precisely as expected for integer and fractional QAH states. Additionally, at zero magnetic field, Rxy is approximately 2h/e2 near half-filling (ν = −1/2) and varies linearly as ν is tuned. This behaviour resembles that of the composite Fermi liquid in the half-filled lowest Landau level of a two-dimensional electron gas at high magnetic field8–14. Direct observation of the fractional QAH and associated effects enables research in charge fractionalization and anyonic statistics at zero magnetic field.

Date: 2023
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DOI: 10.1038/s41586-023-06536-0

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