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For the chiral limit of two sheets of $n$-layer Bernal-stacked graphene established in the Physical Review Letters arXiv:2109.10325 and arXiv:2109.11514, we prove a trichotomy: depending on the twisting angle, we have either (1)…

Mathematical Physics · Physics 2025-08-05 Bryan Li , Mengxuan Yang

When two layers of two-dimensional materials are assembled with a relative twist, moir\'e patterns arise, inducing a tremendous wealth of exotic phenomena. In this work, we consider twisting two triangular lattices hosting Dirac quantum…

Strongly Correlated Electrons · Physics 2022-11-09 Zhu-Xi Luo , Urban F. P. Seifert , Leon Balents

The emergence of flat bands in twisted bilayer graphene at the magic angle can be understood in terms of a vanishing Fermi velocity of the Dirac cone. This is associated with van Hove singularities approaching the Fermi energy and becoming…

Strongly Correlated Electrons · Physics 2023-06-05 A. S. Shankar , D. O. Oriekhov , Andrew K. Mitchell , L. Fritz

We experimentally investigate the band structures of chirally twisted triple bilayer graphene. The new kind of moir\'e structure, formed by three pieces of helically stacked Bernal bilayer graphene, has flat bands at charge neutral point…

Mesoscale and Nanoscale Physics · Physics 2025-01-14 Wenlu Lin , Wenxuan Wang , Shimin Cao , Miao Liang , Lili Zhao , Kenji Watanabe , Takashi Taniguchi , Jinhua Gao , Jianhao Chen , Xiaobo Lu , Yang Liu

Utilizing the established Bistritzer-MacDonald model for twisted bilayer graphene (tBLG), we theoretically investigate the non-Hermitian (NH) topological properties of this in the presence of non-reciprocal (NR) hopping on both layers and…

Mesoscale and Nanoscale Physics · Physics 2025-10-14 Kamalesh Bera , Debasish Mondal , Arijit Saha , Debashree Chowdhury

Despite much theoretical work, developing a comprehensive ab initio model for twisted bilayer graphene (TBG) has proven challenging due to the inherent trade-off between accurately describing the band structure and incorporating the…

Strongly Correlated Electrons · Physics 2025-09-25 Run Hou , Shouvik Sur , Lucas K. Wagner , Andriy H. Nevidomskyy

Starting with twisted bilayer graphene, graphene-based moir\'e materials have recently been established as a new platform for studying strong electron correlations. In this paper, we study twisted graphene monolayers on trilayer graphene…

The low-energy bands of twisted bilayer graphene form Dirac cones with approximate electron-hole symmetry at small rotation angles. These crossings are protected by the emergent symmetries of moir\'e patterns, conferring a topological…

Mesoscale and Nanoscale Physics · Physics 2020-11-25 Hector Ochoa

Magic-angle ($\theta=1.05^\circ$) twisted bilayer graphene (MATBG) has shown two seemingly contradictory characters: the localization and quantum-dot-like behavior in STM experiments, and delocalization in transport experiments. We…

Strongly Correlated Electrons · Physics 2023-01-12 Zhi-Da Song , B. Andrei Bernevig

Our theoretical study unfolds the topological phase transitions (within bands of the Moir\'e super-lattice) in small angle twisted double bilayer graphene (tDBLG) under the influence of external gate voltage and intrinsic spin-orbit…

Mesoscale and Nanoscale Physics · Physics 2025-02-05 Kamalesh Bera , Priyanka Mohan , Arijit Saha

We present a low-energy model describing the reconstruction of the electronic spectrum in twisted bilayers of honeycomb crystals with broken sublattice symmetry. The resulting moir\'e patterns are classified into two families with different…

Mesoscale and Nanoscale Physics · Physics 2020-07-22 H. Ochoa , A. Asenjo-Garcia

In recent experiments, superconductivity and correlated insulating states were observed in twisted bilayer graphene (TBG) with small magic angles, which highlights the importance of the flat bands near Fermi energy. However, the moir\'e…

Materials Science · Physics 2020-02-11 Jing-Yang You , Bo Gu , Gang Su

Twisted bilayer graphene (TBG) features strongly correlated and topological phases due to its flat bands emerging near the magic angle. However, the effects of the non-Hermiticity, arising from the coupling to the environment and…

Mesoscale and Nanoscale Physics · Physics 2025-06-06 Juan Pablo Esparza , Vladimir Juricic

Using exact diagonalization, we study the projected Hamiltonian with Coulomb interaction in the 8 flat bands of first magic angle twisted bilayer graphene. Employing the U(4) (U(4)$\times$U(4)) symmetries in the nonchiral (chiral) flat band…

Strongly Correlated Electrons · Physics 2022-04-26 Fang Xie , Aditya Cowsik , Zhi-Da Song , Biao Lian , B. Andrei Bernevig , Nicolas Regnault

We report on a double moir\'e system consisting of four graphene layers, where the top and bottom pairs form small-twist-angle bilayer graphene, and the middle interface has a large rotational mismatch. This system shows clear signatures of…

We develop a controlled diagrammatic framework for periodic Anderson models,and apply it to heterostrained magic-angle twisted bilayer graphene (MATBG) at charge neutrality using the topological heavy-fermion formulation. Building on…

Strongly Correlated Electrons · Physics 2026-05-29 Eyal Keshet , Yaar Vituri , Erez Berg

Flat bands in moir\'e systems are exciting new playgrounds for the generation and study of exotic many-body physics phenomena in low-dimensional materials. Such physics is attributed to the vanishing kinetic energy and strong spatial…

The discovery of superconductivity in twisted bilayer and twisted trilayer graphene has generated tremendous interest. The key feature of these systems is an interplay between interlayer coupling and a moir\'e superlattice that gives rise…

Twisted bilayer graphene (TBG) provides a unique framework to elucidate the interplay between strong correlations and topological phenomena in two-dimensional systems. The existence of multiple electronic degrees of freedom -- charge, spin,…

Strongly Correlated Electrons · Physics 2021-01-27 Yuan Da Liao , Jian Kang , Clara N. Breiø , Xiao Yan Xu , Han-Qing Wu , Brian M. Andersen , Rafael M. Fernandes , Zi Yang Meng

Twisted bilayer graphene with a twist angle of around 1.1{\deg} features a pair of isolated flat electronic bands and forms a strongly correlated electronic platform. Here, we use scanning tunneling microscopy to probe local properties of…