Thermal conductivity of twisted bilayer graphene

Nanoscale ◽  
2014 ◽  
Vol 6 (22) ◽  
pp. 13402-13408 ◽  
Author(s):  
Hongyang Li ◽  
Hao Ying ◽  
Xiangping Chen ◽  
Denis L. Nika ◽  
Alexandr I. Cocemasov ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Bilayer Graphene ◽  
Graphene Layers ◽  
Twisted Bilayer Graphene ◽  
Heat Carriers

The heat carriers – phonons – in twisted bilayer graphene do not behave in the same manner as that observed in individual graphene layers.

scholarly journals Quasicrystalline 30° twisted bilayer graphene as an incommensurate superlattice with strong interlayer coupling

2018 ◽  
Vol 115 (27) ◽  
pp. 6928-6933 ◽  
Author(s):  
Wei Yao ◽  
Eryin Wang ◽  
Changhua Bao ◽  
Yiou Zhang ◽  
Kenan Zhang ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Graphene Layer ◽  
Rotational Symmetry ◽  
Reciprocal Lattice ◽  
Double Resonance ◽  
Interlayer Coupling ◽  
Bilayer Graphene ◽  
Lattice Vector ◽  
Graphene Layers ◽  
Twisted Bilayer Graphene

The interlayer coupling can be used to engineer the electronic structure of van der Waals heterostructures (superlattices) to obtain properties that are not possible in a single material. So far research in heterostructures has been focused on commensurate superlattices with a long-ranged Moiré period. Incommensurate heterostructures with rotational symmetry but not translational symmetry (in analogy to quasicrystals) are not only rare in nature, but also the interlayer interaction has often been assumed to be negligible due to the lack of phase coherence. Here we report the successful growth of quasicrystalline 30° twisted bilayer graphene (30°-tBLG), which is stabilized by the Pt(111) substrate, and reveal its electronic structure. The 30°-tBLG is confirmed by low energy electron diffraction and the intervalley double-resonance Raman mode at 1383 cm−1. Moreover, the emergence of mirrored Dirac cones inside the Brillouin zone of each graphene layer and a gap opening at the zone boundary suggest that these two graphene layers are coupled via a generalized Umklapp scattering mechanism—that is, scattering of a Dirac cone in one graphene layer by the reciprocal lattice vector of the other graphene layer. Our work highlights the important role of interlayer coupling in incommensurate quasicrystalline superlattices, thereby extending band structure engineering to incommensurate superstructures.

scholarly journals Moire Is Different

2021 ◽  
Vol 13 (1) ◽  
pp. 50
Author(s):  
Wenyuan Shi
Keyword(s):  
Electronic Structures ◽  
Tight Binding ◽  
Physical Property ◽  
Large Change ◽  
Bilayer Graphene ◽  
Dirac Fermion ◽  
Dirac Fermions ◽  
Graphene Layers ◽  
Flat Bands ◽  
Twisted Bilayer Graphene

Graphene, as the thinnest material ever found, exhibits unconventionally relativistic behaviour of Dirac fermions. However, unusual phenomena (such as superconductivity) arise when stacking two graphene layers and twisting the bilayer graphene. The relativistic Dirac fermion in graphene has been widely studied and understood, but the large change observed in twisted bilayer graphene (TBG) is intriguing and still unclear because only van der Waals force (vdW) interlayer interaction is added from graphene to TBG and such a very weak interaction is expected to play a negligible role. To understand such dramatic variation, we studied the electronic structures of monolayer, bilayer and twisted bilayer graphene. Twisted bilayer graphene creates different moiré patterns when turned at different angles. We proposed tight-binding and effective continuum models and thereby drafted a computer code to calculate their electronic structures. Our calculated results show that the electronic structure of twisted bilayer graphene changes significantly even by a tiny twist. When bilayer graphene is twisted at special “magic angles”, flat bands appear. We examined how these flat bands are created, their properties and the relevance to some unconventional physical property such as superconductivity. We conclude that in the nanoscopic scale, similar looking atomic structures can create vastly different electronic structures. Like how P. W. Anderson stated that similar looking fields in science can have differences in his article “More is Different”, similar moiré patterns in twisted bilayer graphene can produce different electronic structures.

scholarly journals Steering the current flow in twisted bilayer graphene

2022 ◽  
Author(s):  
Jesús Arturo Sánchez-Sánchez ◽  
Montserrat Navarro-Espino ◽  
Yonatan Betancur Ocampo ◽  
José Eduardo Barrios Vargas ◽  
Thomas Stegmann
Keyword(s):  
Current Flow ◽  
Twist Angle ◽  
Bottom Layer ◽  
Bilayer Graphene ◽  
Energy Bands ◽  
Initial Direction ◽  
Steering Angle ◽  
Graphene Layers ◽  
Ballistic Electron ◽  
Twisted Bilayer Graphene

Abstract A nanoelectronic device made of twisted bilayer graphene (TBLG) is proposed to steer the direction of the current flow. The ballistic electron current, injected at one edge of the bottom layer, can be guided predominantly to one of the lateral edges of the top layer. The current is steered to the opposite lateral edge, if either the twist angle is reversed or the electrons are injected in the valence band instead of the conduction band, making it possible to control the current flow by electric gates. When both graphene layers are aligned, the current passes straight through the system without changing its initial direction. The observed steering angle exceeds well the twist angle and emerges for a broad range of experimentally accessible parameters. It is explained by the twist angle and the trigonal shape of the energy bands beyond the van Hove singularity due to the Moiré interference pattern. As the shape of the energy bands depends on the valley degree of freedom, the steered current is valley polarized. Our findings show how to control and manipulate the current flow in TBLG. Technologically, they are of relevance for applications in twistronics and valleytronics.

scholarly journals Observation of a flat band and bandgap in millimeter-scale twisted bilayer graphene

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Keiju Sato ◽  
Naoki Hayashi ◽  
Takahiro Ito ◽  
Noriyuki Masago ◽  
Makoto Takamura ◽  
...  
Keyword(s):  
Large Angle ◽  
Bilayer Graphene ◽  
Epitaxial Graphene ◽  
Photoemission Spectroscopy ◽  
Flat Band ◽  
Magic Angle ◽  
Graphene Layers ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Twisted Bilayer Graphene ◽  
Micrometer Scale

AbstractMagic-angle twisted bilayer graphene, consisting of two graphene layers stacked at a special angle, exhibits superconductivity due to the maximized density of states at the energy of the flat band. Generally, experiments on twisted bilayer graphene have been performed using micrometer-scale samples. Here we report the fabrication of twisted bilayer graphene with an area exceeding 3 × 5 mm2 by transferring epitaxial graphene onto another epitaxial graphene, and observation of a flat band and large bandgap using angle-resolved photoemission spectroscopy. Our results suggest that the substrate potential induces both the asymmetrical doping in large angle twisted bilayer graphene and the electron doped nature of the flat band in magic-angle twisted bilayer graphene.

scholarly journals Grain size-dependent thermal conductivity of polycrystalline twisted bilayer graphene

Carbon ◽  
2017 ◽  
Vol 117 ◽  
pp. 367-375 ◽  
Author(s):  
Tej B. Limbu ◽  
Konstanze R. Hahn ◽  
Frank Mendoza ◽  
Satyaprakash Sahoo ◽  
Joshua James Razink ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Bilayer Graphene ◽  
Size Dependent ◽  
Twisted Bilayer Graphene

scholarly journals Correlation-Induced Insulating Topological Phases at Charge Neutrality in Twisted Bilayer Graphene

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuan Da Liao ◽  
Jian Kang ◽  
Clara N. Breiø ◽  
Xiao Yan Xu ◽  
Han-Qing Wu ◽  
...  
Keyword(s):  
Bilayer Graphene ◽  
Topological Phases ◽  
Charge Neutrality ◽  
Twisted Bilayer Graphene

Superflat energy band induced by moiré electric potential in twisted bilayer graphene

2021 ◽  
Vol 103 (16) ◽  
Author(s):  
Jie Cao ◽  
Fenghua Qi ◽  
Hai Yang ◽  
Guojun Jin
Keyword(s):  
Electric Potential ◽  
Energy Band ◽  
Bilayer Graphene ◽  
Twisted Bilayer Graphene

scholarly journals Strange metal behavior of the Hall angle in twisted bilayer graphene

2021 ◽  
Vol 103 (24) ◽  
Author(s):  
Rui Lyu ◽  
Zachary Tuchfeld ◽  
Nishchhal Verma ◽  
Haidong Tian ◽  
Kenji Watanabe ◽  
...  
Keyword(s):  
Bilayer Graphene ◽  
Hall Angle ◽  
Twisted Bilayer Graphene

scholarly journals Correlated insulators in twisted bilayer graphene

2021 ◽  
Vol 103 (12) ◽  
Author(s):  
Ipsita Mandal ◽  
Jia Yao ◽  
Erich J. Mueller
Keyword(s):  
Bilayer Graphene ◽  
Twisted Bilayer Graphene
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