Beyond the Flat-Band Paradigm: Open Orbits as a Route to Correlated States in Dispersive Moiré Minibands
Year: 2026
Type: preprint
Abstract: The realization of fractional Chern insulators has largely relied on isolated flat bands in complex bilayer or multilayer moiré systems with ideal quantum geometry. Whether such phases can emerge in genuinely dispersive bands, and by what mechanism, remains an open question. Here, we propose a mechanism for magnetic-field-induced strong correlations in the highly dispersive bands of monolayer graphene on hexagonal boron nitride. In the low-field classical-to-quantum crossover regime of the second moiré miniband, we show that the interplay of the moiré potential and weak magnetic fields (B < 1.5 T) profoundly alters electron dynamics. Saddle-point van Hove singularities produce extended open orbits that strongly suppress carrier propagation, potentially favoring a regime in which Coulomb interactions become comparatively more important, while weak magnetic fields lift valley degeneracy and trigonal warping redistributes Berry curvature. High-resolution magnetotransport and temperature-dependent measurements reveal fractional-slope transport features and signatures of interaction-driven incompressibility. Because the Hall conductivity is not fully quantized and the longitudinal resistance remains finite, we describe these observations as incipient FCI behavior: transport signatures consistent with a developing fractional Chern insulating state, without claiming a fully developed FCI phase established by complete Hall quantization and vanishing longitudinal resistance. Our results suggest a possible fermiology-driven route toward correlated topological states in dispersive bands in the classical-to-quantum crossover, distinct from the conventional flat-band scenario.
Source: arXiv (Cornell University)
Authors: Wang, Zihao, Perez-Piskunow, Pablo M., Wong, Calvin Pei Yu, Holwill, Matthew, Sun, Hao, Fu, Wei, Hu, Junxiong, Yuntian, Zheng, Xuanrui, Zhang, Taniguchi, T., Watanabe, K., Ariando, A., Yu, Geliang, Lin, Li, Goh, Kuan Eng Johnson, Roche, Stephan, Jung, Jeil, Novoselov, Kostya S., Leconte, Nicolas
Institutions: National University of Singapore, Institute for Functional Intelligent Materials, Institució Catalana de Recerca i Estudis Avançats, Institut Català de Nanociència i Nanotecnologia, Agency for Science, Technology and Research, Centre for Quantum Technologies, Institute of Materials Research and Engineering, University of Manchester, National Institute for Materials Science, National Laboratory of Solid State Microstructures, Nanjing University, University of Seoul
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: Centres de Recerca de Catalunya, Institut Català de Nanociència i Nanotecnologia, European Commission, Agency for Science, Technology and Research, National Research Foundation Singapore, Ministry of Education - Singapore, Generalitat de Catalunya, Korea Institute of Science and Technology Information, Ministry of Education, India, Centre for Quantum Technologies, Agencia Estatal de Investigación, NextGenerationEU
Awards: G1119546765, G1206670709, G1482925484, G1799927510, G2064873908, G2248368415, G2462415295, G2705702041, G2749317096, G280048558, G2988934680, G3005324705, G318412399, G3523121873, G3546882995, G354764522, G3644697027, G3882347383, G4993905653, G5195188938, G554358111, G5922099756, G631184005, G6512472947, G6520718613, G6605876378, G6656126374, G6762955466, G69051668, G6906965799, G7053809664, G7329201713, G8127297844, G833079005, G846571381, G8637226926, G8925525115
OpenAlex ID: W7220688551