scholarly journals Tuning electron correlation in magic-angle twisted bilayer graphene using Coulomb screening

Science ◽  
2021 ◽  
Vol 371 (6535) ◽  
pp. 1261-1265
Author(s):  
Xiaoxue Liu ◽  
Zhi Wang ◽  
K. Watanabe ◽  
T. Taniguchi ◽  
Oskar Vafek ◽  
...  
Keyword(s):  
Coulomb Interaction ◽  
Theoretical Models ◽  
Bilayer Graphene ◽  
Magic Angle ◽  
Thick Barrier ◽  
Close Proximity ◽  
Twisted Bilayer Graphene ◽  
Quantum Phenomena ◽  
The Stability ◽  
Correlated Fermions

Controlling the strength of interactions is essential for studying quantum phenomena emerging in systems of correlated fermions. We introduce a device geometry whereby magic-angle twisted bilayer graphene is placed in close proximity to a Bernal bilayer graphene, separated by a 3-nanometer-thick barrier. By using charge screening from the Bernal bilayer, the strength of electron-electron Coulomb interaction within the twisted bilayer can be continuously tuned. Transport measurements show that tuning Coulomb screening has opposite effects on the insulating and superconducting states: As Coulomb interaction is weakened by screening, the insulating states become less robust, whereas the stability of superconductivity at the optimal doping is enhanced. The results provide important constraints on theoretical models for understanding the mechanism of superconductivity in magic-angle twisted bilayer graphene.

scholarly journals Gate-defined Josephson junctions in magic-angle twisted bilayer graphene

2021 ◽  
Author(s):  
Folkert K. de Vries ◽  
Elías Portolés ◽  
Giulia Zheng ◽  
Takashi Taniguchi ◽  
Kenji Watanabe ◽  
...  
Keyword(s):  
Josephson Junctions ◽  
Bilayer Graphene ◽  
Magic Angle ◽  
Twisted Bilayer Graphene

scholarly journals Lattice collective modes from a continuum model of magic-angle twisted bilayer graphene

2021 ◽  
Vol 104 (3) ◽  
Author(s):  
Ajesh Kumar ◽  
Ming Xie ◽  
A. H. MacDonald
Keyword(s):  
Continuum Model ◽  
Bilayer Graphene ◽  
Collective Modes ◽  
Magic Angle ◽  
Twisted Bilayer Graphene

Raman spectra of twisted bilayer graphene close to the magic angle

2D Materials ◽  
2022 ◽  
Author(s):  
Tiago Campolina Barbosa ◽  
Andreij C. Gadelha ◽  
Douglas A. A. Ohlberg ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Laser Excitation ◽  
Bilayer Graphene ◽  
Geometrical Model ◽  
Excitation Wavelength ◽  
Magic Angle ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Excitation Laser ◽  
Twisted Bilayer Graphene

Abstract In this work, we study the Raman spectra of twisted bilayer graphene samples as a function of their twist-angles (θ), ranging from 0.03º to 3.40º, where local θ are determined by analysis of their associated moiré superlattices, as imaged by scanning microwave impedance microscopy. Three standard excitation laser lines are used (457, 532, and 633 nm wavelengths), and the main Raman active graphene bands (G and 2D) are considered. Our results reveal that electron-phonon interaction influences the G band's linewidth close to the magic angle regardless of laser excitation wavelength. Also, the 2D band lineshape in the θ < 1º regime is dictated by crystal lattice and depends on both the Bernal (AB and BA) stacking bilayer graphene and strain soliton regions (SP) [1]. We propose a geometrical model to explain the 2D lineshape variations, and from it, we estimate the SP width when moving towards the magic angle.

scholarly journals Charge order and broken rotational symmetry in magic-angle twisted bilayer graphene

Nature ◽  
2019 ◽  
Vol 573 (7772) ◽  
pp. 91-95 ◽  
Author(s):  
Yuhang Jiang ◽  
Xinyuan Lai ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
Kristjan Haule ◽  
...  
Keyword(s):  
Rotational Symmetry ◽  
Charge Order ◽  
Bilayer Graphene ◽  
Magic Angle ◽  
Twisted Bilayer Graphene

scholarly journals Slave-rotor theory on magic-angle twisted bilayer graphene

2020 ◽  
Vol 101 (23) ◽  
Author(s):  
Shin-Ming Huang ◽  
Yi-Ping Huang ◽  
Ting-Kuo Lee
Keyword(s):  
Bilayer Graphene ◽  
Magic Angle ◽  
Twisted Bilayer Graphene

scholarly journals Spin density wave and electron nematicity in magic-angle twisted bilayer graphene

2020 ◽  
Vol 102 (15) ◽  
Author(s):  
A. O. Sboychakov ◽  
A. V. Rozhkov ◽  
A. L. Rakhmanov ◽  
Franco Nori
Keyword(s):  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Bilayer Graphene ◽  
Magic Angle ◽  
Twisted Bilayer Graphene

Correlation-induced valley splitting and orbital magnetism in a strain-induced zero-energy flatband in twisted bilayer graphene near the magic angle

2020 ◽  
Vol 102 (8) ◽  
Author(s):  
Yu Zhang ◽  
Zhe Hou ◽  
Ya-Xin Zhao ◽  
Zi-Han Guo ◽  
Yi-Wen Liu ◽  
...  
Keyword(s):  
Bilayer Graphene ◽  
Magic Angle ◽  
Zero Energy ◽  
Valley Splitting ◽  
Orbital Magnetism ◽  
Twisted Bilayer Graphene

scholarly journals Possible correlated insulating states in magic-angle twisted bilayer graphene under strongly competing interactions

2018 ◽  
Vol 98 (8) ◽  
Author(s):  
Masayuki Ochi ◽  
Mikito Koshino ◽  
Kazuhiko Kuroki
Keyword(s):  
Bilayer Graphene ◽  
Magic Angle ◽  
Competing Interactions ◽  
Twisted Bilayer Graphene
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