Remarkable recent experiments on the moiré structure formed by pentalayer rhombohedral graphene aligned with a hexagonal Boron-Nitride substrate report the discovery of a zero field fractional quantum hall effect. These "(Fractional) Quantum Anomalous Hall" ((F)QAH) phases occur for one sign of a perpendicular displacement field, and correspond, experimentally, to full or partial filling of a valley polarized Chern-$1$ band. Such a band is absent in the non-interacting band structure. Here we show that electron-electron interactions play a crucial role, and present microscopic theoretical calculations demonstrating the emergence of a nearly flat, isolated, Chern-$1$ band and FQAH phases in this system. We also study the four and six-layer analogs and identify parameters where a nearly flat isolated Chern-$1$ band emerges which may be suitable to host FQAH physics.
Moiré Fractional Chern Insulators III: Hartree-Fock Phase Diagram, Magic Angle Regime for Chern Insulator States, the Role of the Moiré Potential and Goldstone Gaps in Rhombohedral Graphene Superlattices
Anomalous Hall Crystals in Rhombohedral Multilayer Graphene I: Interaction-Driven Chern Bands and Fractional Quantum Hall States at Zero Magnetic Field
The "Moiré Capacitor Effect" and Stabilization of Fractional Chern Insulators in Rhombohedral Graphene Superlattices
Center for Computational Quantum Physics, Flatiron Institute（Flatiron研究所计算量子物理中心）；Laboratoire de Physique de l’Ecole normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité（巴黎高等师范学院物理实验室，ENS，PSL大学，CNRS，索邦大学，巴黎第七大学，索邦巴黎城）；Department of Physics, Princeton University（普林斯顿大学物理系）；Donostia International Physics Center（圣塞巴斯蒂安国际物理中心）；Princeton Center for Theoretical Science, Princeton University（普林斯顿大学理论科学中心）；Department of Physics, University of Texas at Dallas（德克萨斯大学达拉斯分校物理系）；IKERBASQUE, Basque Foundation for Science（伊卡巴斯基克，巴斯克科学基金会）；Department of Physics, Massachusetts Institute of Technology（麻省理工学院物理系）
Competing Chern states revealed by quasiparticle charging in moiré rhombohedral graphene
Cornell University（康奈尔大学）；Max Planck Institute for the Structure and Dynamics of Matter（马克斯·普朗克物质结构与动力学研究所）；Massachusetts Institute of Technology（麻省理工学院）；Florida State University（佛罗里达州立大学）；National Institute for Materials Science（国立材料研究所）
Charge imprinting biases topology of correlated insulator in hBN-aligned rhombohedral multilayer graphene
University of Chinese Academy of Sciences（中国科学院大学）；Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences（中国科学院理论科学 kavli 研究所）；ShanghaiTech University（上海科技大学）；Liaoning Academy of Materials（辽宁省材料研究院）
Ferromagnetism is most common in transition metal compounds but may also arise in low-density two-dimensional electron systems, with signatures observed in silicon, III-V semiconductor systems, and graphene moiré heterostructures. Here we show that gate-tuned van Hove singularities in rhombohedral trilayer graphene drive the spontaneous ferromagnetic polarization of the electron system into one or more spin- and valley flavors. Using capacitance measurements on graphite-gated van der Waals heterostructures, we find a cascade of density- and electronic displacement field tuned phase transitions…
Competing Orders Driven by Wigner Crystal Phase in Rhombohedral Graphene
Institute of Physics, Ecole Polytechnique Fédérale de Lausanne（洛桑联邦理工学院物理研究所）；SPEC, CEA, CNRS, Université Paris-Saclay（法国原子能和替代能源委员会、国家科学研究中心、萨克雷大学SPEC实验室）；Department of Physics, Florida State University（佛罗里达州立大学物理系）；National High Magnetic Field Laboratory（国家高磁场实验室）；FSU Quantum Initiative, Florida State University（佛罗里达州立大学FSU量子倡议项目）；Research Center for Functional Materials, National Institute for Materials Science（日本物质材料研究机构功能材料研究中心）
Chern number reversal and emergent superconductivity in rhombohedral graphene induced by in-plane magnetic fields
Tsinghua University（清华大学）；Peking University（北京大学）；National Institute for Materials Science（物质材料研究机构）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）；Hefei National Laboratory（合肥国家实验室）
Graphene moire superlattices have emerged as a platform hosting and abundance of correlated insulating, topological, and superconducting phases. While the origins of strong correlations and non-trivial topology are shown to be directly linked to flat moire bands, the nature and mechanism of superconductivity remain enigmatic. In particular, only alternating twisted stacking geometries of bilayer and trilayer graphene are found to exhibit robust superconductivity manifesting as zero resistance and Fraunhofer interference patterns. Here we demonstrate that magic-angle twisted tri-, quadri-, and …
Impurity-induced thermal crossover in fractional Chern insulators
City University of Hong Kong（香港城市大学）；University of Maryland（马里兰大学）；Joint Quantum Institute（联合量子研究所）；Kavli Institute for Theoretical Physics（卡弗里理论物理研究所）；University of California, Santa Barbara（加州大学圣塔芭芭拉分校）
Atomically thin van der Waals materials stacked with an interlayer twist have proven to be an excellent platform towards achieving gate-tunable correlated phenomena linked to the formation of flat electronic bands. In this work we demonstrate the formation of emergent correlated phases in multilayer rhombohedral graphene - a simple material that also exhibits a flat electronic band but without the need of having a moiré superlattice induced by twisted van der Waals layers. We show that two layers of bilayer graphene that are twisted by an arbitrary tiny angle host large (micron-scale) regions …
One-Step Epitaxial Access to Rhombohedral Graphene Flat-Band States on Step-Bunched SiC
Institute for Advanced Studies, Wuhan University（武汉大学高等研究院）；Department of Physics, Southern University of Science and Technology（南方科技大学物理系）；School of Physics and Technology, Wuhan University（武汉大学物理科学与技术学院）
Surface-Selective Probe of Spin-Triplet Superconductivity in Rhombohedral Graphene
Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院物理研究所）；Department of Applied Physics, Aalto University School of Science（阿尔托大学理学院应用物理系）；Research Center for Functional Materials, National Institute for Materials Science（国立材料科学研究所功能材料研究中心）；International Center for Materials Nanoarchitectonics, National Institute for Materials Science（国立材料科学研究所国际纳米材料组装中心）；Braun Center for Submicron Research, Department of Condensed Matter Physics（雷霍沃特凝聚态物理系布朗亚微米研究中心）；Department of Physics, Florida State University（佛罗里达州立大学物理系）；National High Magnetic Field Laboratory（国家高磁场实验室）；Center for Quantum Science and Engineering (QSE Center), École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院量子科学与工程中心）
Motivated by the observation of two distinct superconducting phases in the moiréless ABC-stacked rhombohedral trilayer graphene, we investigate the electron-acoustic-phonon coupling as a possible pairing mechanism. We predict the existence of superconductivity with the highest $T_c\sim 3$K near the Van Hove singularity. Away from the Van Hove singularity, $T_c$ remains finite in a wide range of doping. In our model, the $s$-wave spin-singlet and $f$-wave spin-triplet pairings yield the same $T_c$, while other pairing states have negligible $T_c$. Our theory provides a simple explanation for th…
Self-doped Crystal from Preempted Band-inversion Transitions
Graduate Group in Applied Science & Technology, University of California, Berkeley（加州大学伯克利分校应用科学与技术研究生组）；Department of Physics, Harvard University（哈佛大学物理系）；Department of Physics, University of California, Berkeley（加州大学伯克利分校物理系）
