Extended quantum anomalous Hall states in graphene/hBN moiré superlattices

Zhengguang Lu, Tonghang Han, Yuxuan Yao, Zach Hadjri, Jixiang Yang, Junseok Seo, Lihan Shi, Shenyong Ye, Kenji Watanabe, Takashi Taniguchi and Long Ju ()
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Zhengguang Lu: Massachusetts Institute of Technology
Tonghang Han: Massachusetts Institute of Technology
Yuxuan Yao: Massachusetts Institute of Technology
Zach Hadjri: Massachusetts Institute of Technology
Jixiang Yang: Massachusetts Institute of Technology
Junseok Seo: Massachusetts Institute of Technology
Lihan Shi: Massachusetts Institute of Technology
Shenyong Ye: Massachusetts Institute of Technology
Kenji Watanabe: National Institute for Materials Science
Takashi Taniguchi: National Institute for Materials Science
Long Ju: Massachusetts Institute of Technology

Nature, 2025, vol. 637, issue 8048, 1090-1095

Abstract: Abstract Electrons in topological flat bands can form new topological states driven by correlation effects. The pentalayer rhombohedral graphene/hexagonal boron nitride (hBN) moiré superlattice was shown to host fractional quantum anomalous Hall effect (FQAHE) at approximately 400 mK (ref. 1), triggering discussions around the underlying mechanism and role of moiré effects2–6. In particular, new electron crystal states with non-trivial topology have been proposed3,4,7–15. Here we report electrical transport measurements in rhombohedral pentalayer and tetralayer graphene/hBN moiré superlattices at electronic temperatures down to below 40 mK. We observed two more fractional quantum anomalous Hall (FQAH) states and smaller Rxx values in pentalayer devices than those previously reported. In the new tetralayer device, we observed FQAHE at moiré filling factors v = 3/5 and 2/3. With a small current at the base temperature, we observed a new extended quantum anomalous Hall (EQAH) state and magnetic hysteresis, where Rxy = h/e2 and vanishing Rxx spans a wide range of v from 0.5 to 1.3. At increased temperature or current, EQAH states disappear and partially transition into the FQAH liquid16–18. Furthermore, we observed displacement field-induced quantum phase transitions from the EQAH states to the Fermi liquid, FQAH liquid and the likely composite Fermi liquid. Our observations established a new topological phase of electrons with quantized Hall resistance at zero magnetic field and enriched the emergent quantum phenomena in materials with topological flat bands.

Date: 2025
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DOI: 10.1038/s41586-024-08470-1

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