Extended quantum anomalous Hall states in graphene/hBN moiré superlattices

• 成果类型: Article
• 署名作者: Lu, Zhengguang; Han, Tonghang; Yao, Yuxuan; Hadjri, Zach; Yang, Jixiang; Seo, Junseok; Shi, Lihan; Ye, Shenyong; Watanabe, Kenji; Taniguchi, Takashi; Ju, Long
• 署名单位: Massachusetts Institute of Technology (MIT); State University System of Florida; Florida State University; National Institute for Materials Science; National Institute for Materials Science
• 刊物名称: Nature
• ISSN/ISSBN: 0028-2386
• DOI: 10.1038/s41586-024-08470-1
• 发表日期: 2025-01-30
• 关键词: chern insulator; wigner crystal; band-gap; transport; liquid; phase; TRANSITION; fluid; mott

摘要

Electrons in topological flat bands can form new topological states driven by correlation effects. The pentalayer rhombohedral graphene/hexagonal boron nitride (hBN) moir & eacute; 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 moir & eacute; effects2, 3, 4, 5-6. In particular, new electron crystal states with non-trivial topology have been proposed3,4,7, 8, 9, 10, 11, 12, 13, 14-15. Here we report electrical transport measurements in rhombohedral pentalayer and tetralayer graphene/hBN moir & eacute; 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 moir & eacute; 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, 17-18. 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.