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 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

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 Electronic Properties of Twisted Bilayer Graphene in the Presence of a Magnetic Field

2020 ◽  
Vol 233 ◽  
pp. 03004
Author(s):  
M.F.C. Martins Quintela ◽  
J.C.C. Guerra ◽  
S.M. João
Keyword(s):  
Magnetic Field ◽  
Electronic Properties ◽  
Twist Angle ◽  
Bilayer Graphene ◽  
Polynomial Method ◽  
Zero Energy ◽  
Energy Bands ◽  
Optical And Electronic Properties ◽  
Twisted Bilayer Graphene ◽  
Kernel Polynomial Method

In AA-stacked twisted bilayer graphene, the lower energy bands become completely flat when the twist angle passes through certain specific values: the so-called “magic angles”. The Dirac peak appears at zero energy due to the flattening of these bands when the twist angle is sufficiently small [1-3]. When a constant perpendicular magnetic field is applied, Landau levels start appearing as expected [5]. We used the Kernel Polynomial Method (KPM) [6] as implemented in KITE [7] to study the optical and electronic properties of these systems. The aim of this work is to analyze how the features of these quantities change with the twist angle in the presence of an uniform magnetic field.

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

scholarly journals Magnetism of magic-angle twisted bilayer graphene

2021 ◽  
Vol 11 (4) ◽  
Author(s):  
Javad Vahedi ◽  
Robert Peters ◽  
Ahmed Missaoui ◽  
Andreas Honecker ◽  
Guy Trambly de Laissardière
Keyword(s):  
Mean Field ◽  
Bilayer Graphene ◽  
Real Space ◽  
Localized States ◽  
Magic Angle ◽  
Experimental Realization ◽  
Hartree Fock ◽  
Large Size ◽  
Twisted Bilayer Graphene ◽  
Magnetic States

We investigate magnetic instabilities in charge-neutral twisted bilayer graphene close to so-called ``magic angles’’ using a combination of real-space Hartree-Fock and dynamical mean-field theories. In view of the large size of the unit cell close to magic angles, we examine a previously proposed rescaling that permits to mimic the same underlying flat minibands at larger twist angles. We find that localized magnetic states emerge for values of the Coulomb interaction UU that are significantly smaller than what would be required to render an isolated layer antiferromagnetic. However, this effect is overestimated in the rescaled system, hinting at a complex interplay of flatness of the minibands close to the Fermi level and the spatial extent of the corresponding localized states. Our findings shed new light on perspectives for experimental realization of magnetic states in charge-neutral twisted bilayer graphene.

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