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Two monolayers of graphene twisted by a small `magic' angle exhibit nearly flat bands leading to correlated electronic states and superconductivity, whose precise nature including possible broken symmetries, remain under debate. Here we…

Strongly Correlated Electrons · Physics 2019-12-13 Jong Yeon Lee , Eslam Khalaf , Shang Liu , Xiaomeng Liu , Zeyu Hao , Philip Kim , Ashvin Vishwanath

Unlike the spin-1/2 fermions, the Lieb and Dice lattices both host triply-degenerate low-energy excitations. Here, we discuss Moir\'e structures involving twisted bilayers of these lattices, which are shown to exhibit a tunable number of…

Mesoscale and Nanoscale Physics · Physics 2024-12-05 Xiaoting Zhou , Yi-Chun Hung , Baokai Wang , Arun Bansil

Observation of strong correlations and superconductivity in twisted-bilayer-graphene have stimulated tremendous interest in fundamental and applied physics. In this system, the superposition of two twisted honeycomb lattices, generating a…

Quantum Gases · Physics 2023-03-14 Zengming Meng , Liangwei Wang , Wei Han , Fangde Liu , Kai Wen , Chao Gao , Pengjun Wang , Cheng Chin , Jing Zhang

Two-dimensional atomic crystals can radically change their properties in response to external influences such as substrate orientation or strain, resulting in essentially new materials in terms of the electronic structure. A striking…

Twisted graphene bilayers provide a versatile platform to engineer metamaterials with novel emergent properties by exploiting the resulting geometric moir\'{e} superlattice. Such superlattices are known to host bulk valley currents at tiny…

Mesoscale and Nanoscale Physics · Physics 2019-09-04 T. M. R. Wolf , J. L. Lado , G. Blatter , O. Zilberberg

Twisted double bilayer graphene has recently emerged as an interesting moir\'e material that exhibits strong correlation phenomena that are tunable by an applied electric field. Here we study the atomic and electronic properties of three…

Twisting is a novel technique for creating strongly correlated effects in two-dimensional bilayered materials, and can tunably generate nontrivial topological properties, magnetism, and superconductivity. Magnetism is particularly…

Strongly Correlated Electrons · Physics 2023-07-20 Zhigang Song , Jingshan Qi , Olivia Liebman , Prineha Narang

The low symmetry and anistropic lattice of 1T$'$ WTe$_2$ is responsible for the existence of parallel one-dimensional channels in the moir\'e patterns of twisted bilayers. This gives the opportunity to explore moir\'e physics of a different…

Materials Science · Physics 2024-07-11 Samuel J. Magorrian , Nicholas D. M. Hine

We compute the phase diagram of twisted bilayer graphene near the magic angle where the occurrence of flat bands enhances the effects of electron-electron interactions and thus unleashes strongly-correlated phenomena. Most importantly, we…

Strongly Correlated Electrons · Physics 2018-12-26 Dante M. Kennes , Johannes Lischner , Christoph Karrasch

Small-twist-angle bilayer graphene supports strongly correlated insulating states and superconductivity. Twisted few-layer graphene systems are likely to open up new directions for strong correlation physics in moir\'e superlattices. We…

Materials Science · Physics 2019-07-30 Xiao Li , Fengcheng Wu , Allan H. MacDonald

Materials with flat electronic bands often exhibit exotic quantum phenomena owing to strong correlations. Remarkably, an isolated low-energy flat band can be induced in bilayer graphene by simply rotating the layers to 1.1$^{\circ}$,…

Mesoscale and Nanoscale Physics · Physics 2019-01-29 Matthew Yankowitz , Shaowen Chen , Hryhoriy Polshyn , K. Watanabe , T. Taniguchi , David Graf , Andrea F. Young , Cory R. Dean

So far the physics of moir\'e graphene bilayers at large, incommensurate rotation angles has been considered uninteresting. It has been held that the interlayer coupling in such structures is weak and the system can be thought of as a pair…

Mesoscale and Nanoscale Physics · Physics 2019-11-01 Hridis K. Pal , Stephen Spitz , Markus Kindermann

Two-dimensional (2D) bilayers, twisted to particular angles to display electronic flat bands, are being extensively explored for physics of strongly correlated 2D systems. However, the similar rich physics of one-dimensional (1D) strongly…

Materials Science · Physics 2022-06-06 Sunny Gupta , Henry Yu , Boris I. Yakobson

Twisted graphene bilayers show a complex electronic structure, further modified by interaction effects. The main features can be obtained from effective models, which make use a few phenomenological parameters. We analyze the influence of…

Strongly Correlated Electrons · Physics 2019-03-04 Niels R. Walet , Francisco Guinea

Band engineering in twisted bilayers of the five generic two-dimensional Bravais networks is demonstrated. We first derive symmetry-based constraints on the interlayer coupling, which helps us to predict and understand the shape of the…

Strongly Correlated Electrons · Physics 2019-11-13 Toshikaze Kariyado , Ashvin Vishwanath

The emergence of flat bands in twisted bilayer graphene leads to an enhancement of interaction effects, and thus to insulating and superconducting phases at low temperatures, even though the exact mechanism is still widely debated. The…

Strongly Correlated Electrons · Physics 2019-11-15 Tommaso Cea , Niels R. Walet , Francisco Guinea

We study the atomic structure of twisted bilayer graphene, with very small mismatch angles ($\theta \sim 0.28^0$), a topic of intense recent interest. We use simulations, in which we combine a recently presented semi-empirical potential for…

Materials Science · Physics 2016-11-15 Sandeep K. Jain , Vladimir Juricic , Gerard T. Barkema

The crystal structure of a material creates a periodic potential that electrons move through giving rise to the electronic band structure of the material. When two-dimensional materials are stacked, the twist angle between the layers…

Strongly Correlated Electrons · Physics 2020-07-07 Zhiming Zhang , Yimeng Wang , Kenji Watanabe , Takashi Taniguchi , Keiji Ueno , Emanuel Tutuc , Brian J. LeRoy

We generalize the continuum model for Moir\'e structures made from twisted graphene layers, in order to include lattice relaxation and the formation of channels at very small (marginal) twist angles. We show that a precise description of…

Strongly Correlated Electrons · Physics 2020-02-19 Niels R. Walet , Francisco Guinea

Magic angle twisted bilayer graphene has emerged as a powerful platform for studying strongly correlated electron physics, owing to its almost dispersionless low-energy bands and the ability to tune the band filling by electrostatic gating.…

Mesoscale and Nanoscale Physics · Physics 2021-07-21 Nikhil Tilak , Xinyuan Lai , Shuang Wu , Zhenyuan Zhang , Mingyu Xu , Raquel de Almeida Ribeiro , Paul C Canfield , Eva Y. Andrei