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We consider a family of twisted graphene multilayers consisting of $n$-untwisted chirally stacked layers, e.g., AB, ABC, etc, with a single twist on top of $m$-untwisted {chirally stacked} layers. Upon neglecting both trigonal warping terms…

Strongly Correlated Electrons · Physics 2022-05-20 Patrick J. Ledwith , Ashvin Vishwanath , Eslam Khalaf

In a dilute two-dimensional electron gas, Coulomb interactions can stabilize the formation of a Wigner crystal. Although Wigner crystals are topologically trivial, it has been predicted that electrons in a partially-filled band can break…

Mesoscale and Nanoscale Physics · Physics 2025-03-13 Ruiheng Su , Dacen Waters , Boran Zhou , Kenji Watanabe , Takashi Taniguchi , Ya-Hui Zhang , Matthew Yankowitz , Joshua Folk

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

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…

Trilayer graphene allows systematic control of its electronic structure through stacking sequence and twist geometry, providing a versatile platform for correlated states. Here we report magnetotransport in alternating twisted trilayer…

Mesoscale and Nanoscale Physics · Physics 2026-02-05 Dohun Kim , Gyeoul Lee , Nicolas Leconte , Seyoung Jin , Takashi Taniguchi , Kenji Watanabe , Jeil Jung , Gil Young Cho , Youngwook Kim

Rhombohedral stacked multilayer graphene is an ideal platform to search for correlated electron phenomena, due to its pair of flat bands touching at zero energy and further tunability by an electric field. Furthermore, its valley-dependent…

Mesoscale and Nanoscale Physics · Physics 2024-02-29 Tonghang Han , Zhengguang Lu , Giovanni Scuri , Jiho Sung , Jue Wang , Tianyi Han , Kenji Watanabe , Takashi Taniguchi , Hongkun Park , Long Ju

We investigate an effective model of proximity modified graphene (or symmetrylike materials) with broken time-reversal symmetry. We predict the appearance of quantum anomalous Hall phases by computing bulk band gap and Chern numbers for…

Mesoscale and Nanoscale Physics · Physics 2020-04-07 Petra Högl , Tobias Frank , Klaus Zollner , Denis Kochan , Martin Gmitra , Jaroslav Fabian

The discovery of magic angle twisted bilayer graphene (MATBG) has unveiled a rich variety of superconducting, magnetic and topologically nontrivial phases. The existence of all these phases in one material, and their tunability, has opened…

Mesoscale and Nanoscale Physics · Physics 2021-11-17 Petr Stepanov , Ming Xie , Takashi Taniguchi , Kenji Watanabe , Xiaobo Lu , Allan H. MacDonald , B. Andrei Bernevig , Dmitri K. Efetov

Moir\'e lattices provide a highly tunable platform for exploring the interplay between electronic correlations and band topology. Introducing a second moir\'e pattern extends this paradigm: interference between the two moir\'e patterns…

Electron-electron interactions play an important role in graphene and related systems and can induce exotic quantum states, especially in a stacked bilayer with a small twist angle. For bilayer graphene where the two layers are twisted by a…

Moir\'e structures formed by twisting three layers of graphene with two independent twist angles present an ideal platform for studying correlated quantum phenomena, as an infinite set of angle pairs is predicted to exhibit flat bands.…

We use a lowest Landau level model to study the recent observation of an anomalous Hall effect in twisted bilayer graphene. This effective model is rooted in the occurrence of Chern bands which arise due to the coupling between the graphene…

Strongly Correlated Electrons · Physics 2020-04-28 Nick Bultinck , Shubhayu Chatterjee , Michael P. Zaletel

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

The breaking and enforcing of symmetries is a crucial ingredient in designing topologically robust materials. While magnetic fields can break time-reversal symmetry to create Chern insulators in electronic and microwave systems, at optical…

We perform an extensive exact diagonalization study of interaction driven insulators in spin- and valley-polarized moir\'{e} flat bands of twisted bilayer graphene aligned with its hexagonal boron nitride substrate. In addition to…

Strongly Correlated Electrons · Physics 2021-03-05 Patrick Wilhelm , Thomas C. Lang , Andreas M. Läuchli

The recent observation of the fractional quantum anomalous Hall effect in moir\'e fractional Chern insulators provides an opportunity to investigate zero magnetic field anyons. To potentially realize non-Abelian anyons, one approach is to…

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

Twisted bilayer MoTe2 is a prototypical moire material in which long-wavelength superlattices amplify electron correlations, enabling a wealth of emergent quantum phases. To date, experimental efforts have focused primarily on small twist…

The discovery that the band structure of electronic insulators may be topologically non-trivial has unveiled distinct phases of electronic matter with novel properties. Recently, mechanical lattices have been found to have similarly rich…

Mesoscale and Nanoscale Physics · Physics 2018-10-10 Noah P. Mitchell , Lisa M. Nash , Daniel Hexner , Ari Turner , William T. M. Irvine

Magic-angle twisted bilayer graphene has recently become a thriving material platform realizing correlated electron phenomena taking place within its topological flat bands. Several numerical and analytical methods have been applied to…

Strongly Correlated Electrons · Physics 2021-09-17 Bin-Bin Chen , Yuan Da Liao , Ziyu Chen , Oskar Vafek , Jian Kang , Wei Li , Zi Yang Meng