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Twisted double bilayer graphene (tDBG) has emerged as an especially rich platform for studying strongly correlated and topological states of matter. The material features moir\'e bands that can be continuously deformed by both perpendicular…

Mesoscale and Nanoscale Physics · Physics 2023-12-05 Minhao He , Jiaqi Cai , Ya-Hui Zhang , Yang Liu , Yuhao Li , Takashi Taniguchi , Kenji Watanabe , David H. Cobden , Matthew Yankowitz , Xiaodong Xu

The experimental discoveries of fractional quantum anomalous Hall effects under zero magnetic fields in both transition metal dichalcogenide and pentalayer graphene moir\'e superlattices have aroused significant research interest. In this…

Strongly Correlated Electrons · Physics 2024-09-24 Zhongqing Guo , Xin Lu , Bo Xie , Jianpeng Liu

The quantum Hall effect, fundamental in modern condensed matter physics, continuously inspires new theories and predicts emergent phases of matter. Here we experimentally demonstrate three types of Chern insulators with synthetic dimensions…

Rhombohedral-stacked multilayer graphene aligned with hexagonal boron nitride has emerged as an excellent platform for investigating exotic quantum phenomena arising from the interplay between electron correlations and nontrivial topology.…

Chern insulators are topologically non-trivial states of matter characterized by incompressible bulk and chiral edge states. Incorporating topological Chern bands with strong electronic correlations provides a versatile playground for…

Mesoscale and Nanoscale Physics · Physics 2024-06-14 Qianying Hu , Shu Liang , Xinheng Li , Hao Shi , Xi Dai , Yang Xu

The Hofstadter model is a popular choice for theorists investigating the fractional quantum Hall effect on lattices, due to its simplicity, infinite selection of topological flat bands, and increasing applicability to real materials. In…

Strongly Correlated Electrons · Physics 2021-09-09 Bartholomew Andrews , Titus Neupert , Gunnar Möller

Recent experiments on bilayer graphene twisted near the magic angle have observed spontaneous integer quantum Hall states in the presence of an aligned hexagonal boron nitride (hBN) substrate. These states arise from valley ferromagnetism,…

Strongly Correlated Electrons · Physics 2020-06-18 Patrick J. Ledwith , Grigory Tarnopolsky , Eslam Khalaf , Ashvin Vishwanath

Rhombohedral multilayer graphene, with its flat electronic bands and concentrated Berry curvature, is a promising material for the realization of correlated topological phases of matter. When aligned to an adjacent hexagonal boron nitride…

Mesoscale and Nanoscale Physics · Physics 2025-09-16 Samuel H. Aronson , Tonghang Han , Zhengguang Lu , Yuxuan Yao , Kenji Watanabe , Takashi Taniguchi , Long Ju , Raymond C. Ashoori

Two-dimensional moire materials present unprecedented opportunities to explore quantum phases of matter arising from the interplay of band topology and strong correlations.One of the most striking examples is the recent observation of…

Moir\'e flatbands, occurring, e.g., in twisted bilayer graphene at magic angles, have attracted ample interest due to their high degree of experimental tunability and the intriguing possibility of generating novel strongly interacting…

Mesoscale and Nanoscale Physics · Physics 2020-03-17 Ahmed Abouelkomsan , Zhao Liu , Emil J. Bergholtz

Moir\'e materials have emerged as a powerful platform for exploring exotic quantum phases. While recent experiments have unveiled fractional Chern insulators exhibiting the fractional quantum anomalous Hall effect based on electrons or…

Mesoscale and Nanoscale Physics · Physics 2025-12-05 Raul Perea-Causin , Hui Liu , Emil J. Bergholtz

Magic-angle twisted bilayer graphene (MA-TBG) exhibits intriguing quantum phase transitions triggered by enhanced electron-electron interactions when its flat-bands are partially filled. However, the phases themselves and their connection…

Mesoscale and Nanoscale Physics · Physics 2021-04-14 Shuang Wu , Zhenyuan Zhang , K. Watanabe , T. Taniguchi , Eva Y. Andrei

The long-sought Chern insulators that manifest quantum anomalous Hall effect are typically considered to occur solely in ferromagnets. Here, we theoretically predict the realizability of Chern insulators in antiferromagnets, of which the…

Materials Science · Physics 2024-09-24 Yuntian Liu , Jiayu Li , Qihang Liu

We introduce a second-quantized field theory for Chern insulators in which the Hamiltonian features a static vector potential that has the periodicity of the crystal's lattice and spontaneously breaks time-reversal symmetry in the system's…

Mesoscale and Nanoscale Physics · Physics 2026-01-30 Jason G. Kattan , J. E. Sipe

Quantum anomalous Hall (QAH) insulators are two-dimensional (2D) insulating states exhibiting properties similar to those of quantum Hall states but without external magnetic field. They have quantized Hall conductance $\sigma^H=Ce^2/h$,…

Mesoscale and Nanoscale Physics · Physics 2014-01-29 Chen Fang , Matthew J. Gilbert , B. Andrei Bernevig

Chern insulators host topologically protected chiral edge currents with quantized conductance characterized by their Chern number. Switching the chirality of a Chern insulator, namely, the direction of the edge current, is highly…

The quantum anomalous Hall (QAH) state is a two-dimensional topological insulating state that has quantized Hall resistance of h/Ce2 and vanishing longitudinal resistance under zero magnetic field, where C is called the Chern number. The…

The interplay between strong electron-electron interactions and band topology can lead to novel electronic states that spontaneously break symmetries. The discovery of flat bands in magic-angle twisted bilayer graphene (MATBG) with…

Fractional Chern insulators are theoretically predicted states of electronic matter with emergent topological order. They exhibit the same universal properties as the fractional quantum Hall effect, but dispose of the need to apply a strong…

Strongly Correlated Electrons · Physics 2014-05-08 Adolfo G. Grushin , Álvaro Gómez-León , Titus Neupert

Topological insulators and their intriguing edge states can be understood in a single-particle picture and can as such be exhaustively classified. Interactions significantly complicate this picture and can lead to entirely new insulating…

Strongly Correlated Electrons · Physics 2013-09-10 Emil J. Bergholtz , Zhao Liu