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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

Magic-angle twisted bilayer graphene (MATBG) exhibits a range of correlated phenomena that originate from strong electron-electron interactions. These interactions make the Fermi surface highly susceptible to reconstruction when $ \pm 1,…

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

The flat electronic bands in magic-angle twisted bilayer graphene (MATBG) host a variety of correlated insulating ground states, many of which are predicted to support charged excitations with topologically non-trivial spin and/or valley…

We identify states favored by Coulomb interactions projected onto the Wannier basis of the four narrow bands of the "magic angle" twisted bilayer graphene. At the filling of two electrons/holes per moire unit cell, such interactions favor…

Strongly Correlated Electrons · Physics 2019-06-20 Jian Kang , Oskar Vafek

In magic angle twisted bilayer graphene, electron-electron interactions play a central role resulting in correlated insulating states at certain integer fillings. Identifying the nature of these insulators is a central question and…

Strongly Correlated Electrons · Physics 2020-08-19 Nick Bultinck , Eslam Khalaf , Shang Liu , Shubhayu Chatterjee , Ashvin Vishwanath , Michael P. Zaletel

We study thermal fluctuations of a free-standing bilayer graphene subject to vanishing external tension. Within a phenomenological theory, the system is described as a stack of two continuum crystalline membranes, characterized by finite…

Mesoscale and Nanoscale Physics · Physics 2020-12-01 Achille Mauri , David Soriano , Mikhail I. Katsnelson

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

Motivated by recent advances in the fabrication of twisted bilayers of 2D materials, we consider the low-energy properties of a twisted pair of two-dimensional nodal superconductors. We study both the cases of singlet and triplet…

Superconductivity · Physics 2023-07-18 Pavel A. Volkov , Justin H. Wilson , Kevin Lucht , J. H. Pixley

Using non-perturbative theoretical method, we address the problem of strong correlations in twisted bilayer-layer graphene at the magic angle. We concentrate on the solution without symmetry breaking, where conventional Mott insulating…

Strongly Correlated Electrons · Physics 2019-01-29 M. Haule , E. Y. Andrei , K. Haule

AA-stacked bilayer graphene supports Fermi circles in its bonding and antibonding bands which coincide exactly, leading to symmetry-breaking in the presence of electron-electron interactions. We analyze a continuum model of this system in…

Mesoscale and Nanoscale Physics · Physics 2013-04-02 L. Brey , H. A. Fertig

Twisted bilayered graphenes at magic angles are systems housing long ranged periodicity of Moir\'e pattern together with short ranged periodicity associated with the individual graphenes. Such materials are a fertile ground for novel states…

Mesoscale and Nanoscale Physics · Physics 2022-10-11 Pablo Rodriguez-Lopez , Dai-Nam Le , María J. Calderón , Elena Bascones , Lilia M. Woods

The effects of topology and electron-electron interactions on the phase diagram of ABC stacked trilayer graphene (TLG) at the neutrality point are investigated within a weak coupling renormalization group approach. We find that the leading…

Strongly Correlated Electrons · Physics 2012-10-19 Vladimir Cvetkovic , Oskar Vafek

Experimental demonstrations of tunable correlation effects in magic-angle twisted bilayer graphene have put two-dimensional moir\'e quantum materials at the forefront of condensed-matter research. Other twisted few-layer graphitic…

Strongly Correlated Electrons · Physics 2021-08-27 Michael M. Scherer , Dante M. Kennes , Laura Classen

We theoretically study the correlated insulator states, quantum anomalous Hall (QAH) states, and field-induced topological transitions between different correlated states in twisted multilayer graphene systems. Taking twisted…

Mesoscale and Nanoscale Physics · Physics 2022-06-02 Shihao Zhang , Xi Dai , Jianpeng Liu

Twisted bilayer graphene near the magic angle is known to have a cascade of insulating phases at integer filling factors of the low-energy bands. In this Letter we address the nature of these phases through an unrestricted, large-scale…

Strongly Correlated Electrons · Physics 2024-09-30 Khagendra Adhikari , Kangjun Seo , K. S. D. Beach , Bruno Uchoa

We show that unconventional nematic superconductors with multi-component order parameter in lattices with three-fold and six-fold rotational symmetries support a charge-$4e$ vestigial superconducting phase above $T_c$. The charge-$4e$…

Superconductivity · Physics 2021-07-28 Rafael M. Fernandes , Liang Fu

We present a framework for understanding the recently observed cascade transitions and the Landau level degeneracies at every integer filling of twisted bilayer graphene. The Coulomb interaction projected onto narrow bands causes the…

Strongly Correlated Electrons · Physics 2022-01-05 Jian Kang , B. Andrei Bernevig , Oskar Vafek

We reveal a striking correspondence between electron- and phonon-driven pairing in twisted bilayer graphene (TBG) by mapping an atomistic electronically driven pairing model onto an effective inter-valley, intra-Chern description,…

Superconductivity · Physics 2026-03-09 Lucas Baldo , Patric Holmvall , Annica M. Black-Schaffer

We report on the observation of negative electronic compressibility in twisted bilayer graphene for Fermi energies close to insulating states. To observe this negative compressibility, we take advantage of naturally occurring twist angle…