scholarly journals Band structure and topological properties of twisted double bilayer graphene

2019 ◽  
Vol 99 (23) ◽  
Author(s):  
Mikito Koshino
Keyword(s):  
Band Structure ◽  
Bilayer Graphene ◽  
Topological Properties

scholarly journals Effect of Deformation on Topological Properties of Cobalt Monosilicide

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 143
Author(s):  
Sergey Nikolaev ◽  
Dmitry Pshenay-Severin ◽  
Yuri Ivanov ◽  
Alexander Burkov
Keyword(s):  
Band Structure ◽  
Ab Initio Calculations ◽  
Topological Charge ◽  
External Stress ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Topological Properties ◽  
Uniaxial Deformation ◽  
Band Crossing ◽  
Topological Charges

Recently, it was shown that materials with certain crystal structures can exhibit multifold band crossings with large topological charges. CoSi is one such material that belongs to non-centrosymmetric space group P213 (#198) and posseses multifold band crossing points with a topological charge of 4. The change of crystal symmetry, e.g., by means of external stress, can lift the degeneracy and change its topological properties. In the present work, the influence of uniaxial deformation on the band structure and topological properties of CoSi is investigated on the base of ab initio calculations. The k·p Hamiltonian taking into account deformation is constructed on the base of symmetry consideration near the Γ and R points both with and without spin-orbit coupling. The transformation of multifold band crossings into nodes of other types with different topological charges, their shift both in energy and in reciprocal space and the tilt of dispersion around nodes are studied in detail depending on the direction of uniaxial deformation.

scholarly journals Spectroscopy of a tunable moiré system with a correlated and topological flat band

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xiaomeng Liu ◽  
Cheng-Li Chiu ◽  
Jong Yeon Lee ◽  
Gelareh Farahi ◽  
Kenji Watanabe ◽  
...  
Keyword(s):  
Band Structure ◽  
Twist Angle ◽  
Bilayer Graphene ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Flat Band ◽  
Correlated Electron ◽  
Partial Filling ◽  
Valley Polarization ◽  
Spectroscopic Signatures

AbstractMoiré superlattices created by the twisted stacking of two-dimensional crystals can host electronic bands with flat energy dispersion in which enhanced interactions promote correlated electron states. The twisted double bilayer graphene (TDBG), where two Bernal bilayer graphene are stacked with a twist angle, is such a moiré system with tunable flat bands. Here, we use gate-tuned scanning tunneling spectroscopy to directly demonstrate the tunability of the band structure of TDBG with an electric field and to show spectroscopic signatures of electronic correlations and topology for its flat band. Our spectroscopic experiments are in agreement with a continuum model of TDBG band structure and reveal signatures of a correlated insulator gap at partial filling of its isolated flat band. The topological properties of this flat band are probed with the application of a magnetic field, which leads to valley polarization and the splitting of Chern bands with a large effective g-factor.

scholarly journals Band Structure Asymmetry of Bilayer Graphene Revealed by Infrared Spectroscopy

2009 ◽  
Vol 102 (3) ◽  
Author(s):  
Z. Q. Li ◽  
E. A. Henriksen ◽  
Z. Jiang ◽  
Z. Hao ◽  
M. C. Martin ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Band Structure ◽  
Bilayer Graphene

scholarly journals Electronic band structure of magnetic bilayer graphene superlattices

2014 ◽  
Vol 116 (12) ◽  
pp. 123707 ◽  
Author(s):  
C. Huy Pham ◽  
T. Thuong Nguyen ◽  
V. Lien Nguyen
Keyword(s):  
Band Structure ◽  
Electronic Band Structure ◽  
Bilayer Graphene ◽  
Electronic Band

scholarly journals Electronic properties of twisted bilayer graphene in high-energy k ⋅p-Hamiltonian approximation

2020 ◽  
Vol 34 (19n20) ◽  
pp. 2040055
Author(s):  
H. V. Grushevskaya ◽  
G. G. Krylov ◽  
H.-Y. Choi ◽  
S. P. Kruchinin
Keyword(s):  
Band Structure ◽  
Rotation Angle ◽  
Energy Gap ◽  
High Energy ◽  
Bilayer Graphene ◽  
Monolayer Graphene ◽  
Abelian Gauge ◽  
Relativistic Approach ◽  
Energy Formula ◽  
Twisted Bilayer Graphene

A model of twisted bilayer graphene has been offered on the base of developed quasi-relativistic approach with high energy [Formula: see text]-Hamiltonian. Monolayer-graphene twist is accounted as a perturbation of monolayer-graphene Hamiltonian in such a way that at a given point of the Brillouin zone there exists an external non-Abelian gauge field of another monolayer. Majorana-like resonances have been revealed in the band structure of model at a magic rotation angle [Formula: see text]. The simulations have also shown that a superlattice energy gap existing at a rotation angle [Formula: see text] vanishes at a rotation angle [Formula: see text].

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