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Magic-angle twisted bilayer graphene is a tunable material with remarkably flat energy bands near the Fermi level, leading to fascinating transport properties and correlated states at low temperatures. However, grown pristine samples of…

Mesoscale and Nanoscale Physics · Physics 2024-03-29 Aleksander Sanjuan Ciepielewski , Jakub Tworzydło , Timo Hyart , Alexander Lau

We report a strain-controlled tuning of magnetism in transition-metal-atom-decorated graphene. Our first-principles calculations demonstrate that strain can lead to a sudden change in the magnetic configuration of a transition metal (TM)…

Mesoscale and Nanoscale Physics · Physics 2011-08-09 Bing Huang , Jaejun Yu , Su-Huai Wei

We study the temperature dependent magnetic susceptibility of a strained graphene quantum dot by using the determinant quantum Monte Carlo method. Within the Hubbard model on a honeycomb lattice, our unbiased numerical results show that a…

Strongly Correlated Electrons · Physics 2015-02-13 Shuai Cheng , Jinming Yu , Tianxing Ma , N. M. R. Peres

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

Marginally twisted bilayer graphene having small twist angles is predicted to exhibit unique structural and electronic properties, though experimental characterization remains limited. Using scanning tunneling microscopy, we investigate…

The valleys in hexagonal two-dimensional systems with broken inversion symmetry carry an intrinsic orbital magnetic moment. Despite this, such systems possess zero net magnetization unless additional symmetries are broken, since the…

Mesoscale and Nanoscale Physics · Physics 2021-06-30 Brian T. Schaefer , Katja C. Nowack

An extended Hubbard model on a honeycomb lattice with two orbitals per site at charge neutrality is investigated with unbiased large-scale quantum Monte Carlo simulations. The Fermi velocity of the Dirac fermions is renormalized as the…

Strongly Correlated Electrons · Physics 2019-10-11 Yuan Da Liao , Zi Yang Meng , Xiao Yan Xu

Van der Waals heteroepitaxy allows deterministic control over lattice mismatch or azimuthal orientation between atomic layers to produce long wavelength superlattices. The resulting electronic phases depend critically on the superlattice…

Using scanning probe microscopy and spectroscopy, we explore the spatial symmetry of the electronic wavefunctions of twisted bilayer graphene at the "magic angle" of 1.1 degrees. This small twist angle leads to a long wavelength moir\'e…

Mesoscale and Nanoscale Physics · Physics 2020-08-12 Zhiming Zhang , Rachel Myers , Kenji Watanabe , Takashi Taniguchi , Brian J. LeRoy

We consider a lattice model of twisted bilayer graphene (TBG) for incommensurate twist angles, focusing on the role of large-momentum-transfer Umklapp terms. These terms, which nearly connect the Fermi points of different layers, are…

Strongly Correlated Electrons · Physics 2026-03-31 Ian Jauslin , Vieri Mastropietro

For controlling the critical electric fields of the topological phase transition in single bilayer Bi(111), we investigated topological phases in a strained system through first-principles calculations. We found a quadratic band touching…

Mesoscale and Nanoscale Physics · Physics 2019-06-20 Hikaru Sawahata , Naoya Yamaguchi , Fumiyuki Ishii

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

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…

The understanding of quantum many-body states in twisted bilayer graphene at the magic angle has been greatly improved both in experiment and in theory. However, away from the exactly solvable chiral limit and the sign-problem-free charge…

Strongly Correlated Electrons · Physics 2026-05-21 Cheng Huang , Yves H. Kwan , Maksim Ulybyshev , Fakher F. Assaad , Laura Classen , Zi Yang Meng

Magic-angle twisted bilayer graphene (TBG), with rotational misalignment close to 1.1$^\circ$, features isolated flat electronic bands that host a rich phase diagram of correlated insulating, superconducting, ferromagnetic, and topological…

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

Much of the focus of modern condensed matter physics concerns control of quantum phases with examples that include flat band superconductivity in graphene bilayers, the interplay of magnetism and ferroelectricity, and induction of…

Superconductivity · Physics 2020-01-01 Chloe Herrera , Jonah Cerbin , Kirsty Dunnett , Alexander V. Balatsky , Ilya Sochnikov

We explore in detail the electronic phases of a system consisting of three non-colinear arrays of coupled quantum wires, each rotated 120 degrees with respect to the next. A perturbative renormalization-group analysis reveals that multiple…

Strongly Correlated Electrons · Physics 2020-04-29 Chuan Chen , A. H. Castro Neto , Vitor M. Pereira

We investigate the effect of a magnetic field on the band structure of bilayer graphene with a magic twist angle of 1.08{\deg}. The coupling of a tight-binding model and the Peierls phase allows the calculation of the energy bands of…

Mesoscale and Nanoscale Physics · Physics 2024-05-20 Gaëlle Bigeard , Alessandro Cresti

Breakthroughs in two-dimensional van der Waals heterostructures have revealed that twisting creates a moir\'e pattern that quenches the kinetic energy of electrons, allowing for exotic many-body states. We show that cold-atomic, trapped…

Strongly Correlated Electrons · Physics 2020-11-12 Yixing Fu , E. J. König , J. H. Wilson , Yang-Zhi Chou , J. H. Pixley