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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

Motivated by the higher Chern bands of twisted graphene multilayers, we consider flat bands with arbitrary Chern number $C$ with ideal quantum geometry. While $C>1$ bands differ from Landau levels, we show that these bands host exact…

Mesoscale and Nanoscale Physics · Physics 2023-07-25 Junkai Dong , Patrick J. Ledwith , Eslam Khalaf , Jong Yeon Lee , 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

At partial filling of a flat band, strong electronic interactions may favor gapped states harboring emergent topology with quantized Hall conductivity. Emergent topological states have been found in partially filled Landau levels and…

The rapid development of moir\'e quantum matter has recently led to the remarkable discovery of the fractional quantum anomalous Hall effect, and sparked predictions of other novel correlation-driven topological states. Here, we investigate…

Fractional Chern insulators realize the remarkable physics of the fractional quantum Hall effect (FQHE) in crystalline systems with Chern bands. The lowest Landau level (LLL) is known to host the FQHE, but not all Chern bands are suitable…

Strongly Correlated Electrons · Physics 2024-04-22 Patrick J. Ledwith , Ashvin Vishwanath , Daniel E. Parker

Topologically ordered phases are characterized by long-range quantum entanglement and fractional statistics rather than by symmetry breaking. First observed in a fractionally filled continuum Landau level, topological order has since been…

Fractional Chern insulators are lattice analogs of fractional quantum Hall states that realize fractionalized quasiparticles without an external magnetic field. A key strategy to understand and design these phases is to map Chern bands onto…

Mesoscale and Nanoscale Physics · Physics 2026-05-19 Bohao Li , Yunze Ouyang , Fengcheng Wu

Recent developments in fractional quantum Hall (FQH) physics highlight the importance of studying FQH phases of particles partially occupying energy bands that are not Landau levels. FQH phases in the regime of strong lattice effects,…

Strongly Correlated Electrons · Physics 2022-02-04 David Bauer , Spenser Talkington , Fenner Harper , Bartholomew Andrews , Rahul Roy

Chern insulator or quantum anomalous Hall state is a topological state with integer Hall conductivity but in absence of Landau level. It had been well established on various two-dimensional lattices with periodic structure. Here, we report…

Mesoscale and Nanoscale Physics · Physics 2020-01-08 Ai-Lei He , Lu-Rong Ding , Yuan Zhou , Yi-Fei Wang , Chang-De Gong

We study the formation and properties of perfectly-flat zero energy bands in a multi-layer graphene systems in the chiral limit. Employing the degrees of freedoms of the multi-layer system, such as relative twist-angle and relative shifts,…

Mesoscale and Nanoscale Physics · Physics 2024-04-25 Roi Makov , Francisco Guinea , Ady Stern

The Harper-Hofstadter model provides a fractal spectrum containing topological bands of any integer Chern number, $C$. We study the many-body physics that is realized by interacting particles occupying Harper-Hofstadter bands with $|C|>1$.…

Strongly Correlated Electrons · Physics 2015-09-28 Gunnar Möller , Nigel R. Cooper

Recent theoretical works have demonstrated various robust Abelian and non-Abelian fractional topological phases in lattice models with topological flat bands carrying Chern number C=1. Here we study hard-core bosons and interacting fermions…

Strongly Correlated Electrons · Physics 2012-11-07 Yi-Fei Wang , Hong Yao , Chang-De Gong , D. N. Sheng

We consider twisted bilayer graphene on a transition metal dichalcogenide substrate, where proximity-induced spin-orbit coupling significantly alters the eight flat bands which occur near the magic angle. The resulting band structure…

Strongly Correlated Electrons · Physics 2020-12-24 Tianle Wang , Nick Bultinck , Michael P. Zaletel

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 formulate a Chern-Simons composite fermion theory for Fractional Chern Insulators (FCIs), whereby bare fermions are mapped into composite fermions coupled to a lattice Chern-Simons gauge theory. We apply this construction to a Chern…

Strongly Correlated Electrons · Physics 2018-04-10 Ramanjit Sohal , Luiz H. Santos , Eduardo Fradkin

As lattice analogs of fractional quantum Hall systems, fractional Chern insulators (FCIs) exhibit enigmatic physical properties resulting from the intricate interplay between single-body and many-body physics. In particular, the design of…

Strongly Correlated Electrons · Physics 2017-10-31 Ching Hua Lee , Martin Claassen , Ronny Thomale

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

We demonstrate that a Chern insulator could be realized on a real two-dimensional lattice of an organic Dirac semimetal {\alpha}-(BEDT-TTF)2I3 by introducing potential and magnetic modulations in a unit cell. It is a…

Materials Science · Physics 2017-11-22 Toshihito Osada

Two-dimensional moir\'e Chern bands provide an exceptional platform for exploring a variety of many-body quantum phases at zero magnetic field within a lattice system. One particular intriguing possibility is that flat Chern bands can, in…