scholarly journals Failure of Nielsen-Ninomiya Theorem and Fragile Topology in Two-Dimensional Systems with Space-Time Inversion Symmetry: Application to Twisted Bilayer Graphene at Magic Angle

2019 ◽  
Vol 9 (2) ◽  
Author(s):  
Junyeong Ahn ◽  
Sungjoon Park ◽  
Bohm-Jung Yang
Keyword(s):  
Bilayer Graphene ◽  
Space Time ◽  
Magic Angle ◽  
Inversion Symmetry ◽  
Time Inversion ◽  
Two Dimensional ◽  
Twisted Bilayer Graphene

scholarly journals Multiple flat bands and topological Hofstadter butterfly in twisted bilayer graphene close to the second magic angle

2021 ◽  
Vol 118 (30) ◽  
pp. e2100006118
Author(s):  
Xiaobo Lu ◽  
Biao Lian ◽  
Gaurav Chaudhary ◽  
Benjamin A. Piot ◽  
Giulio Romagnoli ◽  
...  
Keyword(s):  
Condensed Matter ◽  
Bilayer Graphene ◽  
Band Gaps ◽  
Magic Angle ◽  
Two Dimensional ◽  
Quantum Phases ◽  
Electron Band ◽  
Flat Bands ◽  
Twisted Bilayer Graphene ◽  
Hofstadter Butterfly

Moiré superlattices in two-dimensional van der Waals heterostructures provide an efficient way to engineer electron band properties. The recent discovery of exotic quantum phases and their interplay in twisted bilayer graphene (tBLG) has made this moiré system one of the most renowned condensed matter platforms. So far studies of tBLG have been mostly focused on the lowest two flat moiré bands at the first magic angle θm1 ∼ 1.1°, leaving high-order moiré bands and magic angles largely unexplored. Here we report an observation of multiple well-isolated flat moiré bands in tBLG close to the second magic angle θm2 ∼ 0.5°, which cannot be explained without considering electron–election interactions. With high magnetic field magnetotransport measurements we further reveal an energetically unbound Hofstadter butterfly spectrum in which continuously extended quantized Landau level gaps cross all trivial band gaps. The connected Hofstadter butterfly strongly evidences the topologically nontrivial textures of the multiple moiré bands. Overall, our work provides a perspective for understanding the quantum phases in tBLG and the fractal Hofstadter spectra of multiple topological bands.

scholarly journals Two-Dimensional Dirac Fermions Protected by Space-Time Inversion Symmetry in Black Phosphorus

2017 ◽  
Vol 119 (22) ◽  
Author(s):  
Jimin Kim ◽  
Seung Su Baik ◽  
Sung Won Jung ◽  
Yeongsup Sohn ◽  
Sae Hee Ryu ◽  
...  
Keyword(s):  
Space Time ◽  
Black Phosphorus ◽  
Inversion Symmetry ◽  
Time Inversion ◽  
Dirac Fermions ◽  
Two Dimensional

scholarly journals Unfolding energy spectra of double-periodicity two-dimensional systems: Twisted bilayer graphene and MoS2 on graphene

2018 ◽  
Vol 2 (1) ◽  
Author(s):  
Yu-ichiro Matsushita ◽  
Hirofumi Nishi ◽  
Jun-ichi Iwata ◽  
Taichi Kosugi ◽  
Atsushi Oshiyama
Keyword(s):  
Bilayer Graphene ◽  
Energy Spectra ◽  
Two Dimensional ◽  
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

Stability and superconductivity of Ca-intercalated bilayer blue phosphorene

2021 ◽  
Author(s):  
Artur Durajski ◽  
Kamil Skoczylas ◽  
Radoslaw Szczesniak
Keyword(s):  
Superconducting State ◽  
Potential Application ◽  
Recent Experiment ◽  
Superconducting Devices ◽  
Bilayer Graphene ◽  
Two Dimensional ◽  
Twisted Bilayer Graphene ◽  
Blue Phosphorene

Superconductivity attracts much interest in two-dimensional compounds due to their potential application in nano-superconducting devices. Inspired by a recent experiment reporting the superconducting state in twisted bilayer graphene, here, based...

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.

Sign in / Sign up

Export Citation Format

Share Document