scholarly journals Twistronics in Graphene, from Transfer Assembly to Epitaxy

2020 ◽  
Vol 10 (14) ◽  
pp. 4690 ◽  
Author(s):  
Di Wu ◽  
Yi Pan ◽  
Tai Min
Keyword(s):  
2D Materials ◽  
Condensed Matter ◽  
Charge Order ◽  
Flat Band ◽  
Monolayer Graphene ◽  
Multilayer Graphene ◽  
The Novel ◽  
Flat Bands ◽  
Layer Graphene ◽  
Bloch Electrons

The twistronics, which is arising from the moiré superlattice of the small angle between twisted bilayers of 2D materials like graphene, has attracted much attention in the field of 2D materials and condensed matter physics. The novel physical properties in such systems, like unconventional superconductivity, come from the dispersionless flat band that appears when the twist reaches some magic angles. By tuning the filling of the fourfold degeneracy flat bands, the desired effects are induced due to the strong correlation of the degenerated Bloch electrons. In this article, we review the twistronics in twisted bi- and multi-layer graphene (TBG and TMG), which is formed both by transfer assembly of exfoliated monolayer graphene and epitaxial growth of multilayer graphene on SiC substrates. Starting from a brief history, we then introduce the theory of flat band in TBG. In the following, we focus on the major achievements in this field: (a) van Hove singularities and charge order; (b) superconductivity and Mott insulator in TBG and (c) transport properties in TBG. In the end, we give the perspective of the rising materials system of twistronics, epitaxial multilayer graphene on the SiC.

scholarly journals Towards holographic flat bands

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Nicolás Grandi ◽  
Vladimir Juričić ◽  
Ignacio Salazar Landea ◽  
Rodrigo Soto-Garrido
Keyword(s):  
Chemical Potential ◽  
Condensed Matter ◽  
Anomalous Hall Effect ◽  
Spectral Weight ◽  
Flat Band ◽  
Dirac Fermion ◽  
Holographic Model ◽  
Quantum Phases ◽  
Flat Bands ◽  
Dirac Systems

Abstract Motivated by the phenomenology in the condensed-matter flat-band Dirac systems, we here construct a holographic model that imprints the symmetry breaking pattern of a rather simple Dirac fermion model at zero chemical potential. In the bulk we explicitly include the backreaction to the corresponding Lifshitz geometry and compute the dynamical critical exponent. Most importantly, we find that such a geometry is unstable towards a nematic phase, exhibiting an anomalous Hall effect and featuring a Drude-like shift of its spectral weight. Our findings should motivate further studies of the quantum phases emerging from such holographic models.

Emerging flat bands in large-angle twisted bi-layer graphene under pressures

Nanoscale ◽  
2021 ◽  
Author(s):  
Liangbing Ge ◽  
Ni Kun ◽  
Xiaojun Wu ◽  
Zhengping Fu ◽  
Yalin Lu ◽  
...  
Keyword(s):  
Large Angle ◽  
Magic Angle ◽  
Unconventional Superconductivity ◽  
Flat Bands ◽  
Layer Graphene

Recent experiments on magic-angle twisted bi-layer graphene have attracted an intensive attention due to exotic properties such as unconventional superconductivity and correlated insulation. These phenomena were often found at a...

scholarly journals Thermophysical Properties of the Novel 2D Materials Graphene and Silicene: Insights from Ab-initio Calculations

2014 ◽  
Vol 45 ◽  
pp. 512-517 ◽  
Author(s):  
Paola Gori ◽  
Olivia Pulci ◽  
Roberto de Lieto Vollaro ◽  
Claudia Guattari
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Thermophysical Properties ◽  
2D Materials ◽  
The Novel

scholarly journals Energy loss by fast-travelling charged particles traversing two-dimensional materials

2020 ◽  
Vol 233 ◽  
pp. 03005
Author(s):  
Jaime E. Santos ◽  
Mikhail Vasilevskiy ◽  
Nuno M.R. Peres ◽  
Antti-Pekka Jauho
Keyword(s):  
Thin Films ◽  
Energy Loss ◽  
2D Materials ◽  
Charged Particles ◽  
Monolayer Graphene ◽  
Two Dimensional ◽  
Particle Detection ◽  
Hydrodynamic Approximation ◽  
Radiation Losses ◽  
Two Dimensional Materials

We consider the problem of the radiation losses by fast-traveling particles traversing two-dimensional (2d) materials or thin films. After review¬ing the screening of electromagnetic fields by two dimensional conducting ma¬terials, we obtain the energy loss by a fast particle traversing such a material or film. In particular, we discuss the pattern of radiation emitted by monolayer graphene treated within a hydrodynamic approximation. These results are com¬pared with recent published results using similar approximations and, having in mind a potential application to particle detection, we briefly discuss how one can improve on the signals obtained by using other two-dimensional materials.

scholarly journals Flat Band and Hole-induced Ferromagnetism in a Novel Carbon Monolayer

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jing-Yang You ◽  
Bo Gu ◽  
Gang Su
Keyword(s):  
Density Functional ◽  
Doping Concentration ◽  
Carbon Materials ◽  
Density Functional Theory Calculations ◽  
Hole Doping ◽  
Flat Band ◽  
Ferromagnetic Transition ◽  
Functional Theory ◽  
Flat Bands ◽  
Half Metal

AbstractIn recent experiments, superconductivity and correlated insulating states were observed in twisted bilayer graphene (TBG) with small magic angles, which highlights the importance of the flat bands near Fermi energy. However, the moiré pattern of TBG consists of more than ten thousand carbon atoms that is not easy to handle with conventional methods. By density functional theory calculations, we obtain a flat band at EF in a novel carbon monolayer coined as cyclicgraphdiyne with the unit cell of eighteen atoms. By doping holes into cyclicgraphdiyne to make the flat band partially occupied, we find that cyclicgraphdiyne with 1/8, 1/4, 3/8 and 1/2 hole doping concentration shows ferromagnetism (half-metal) while the case without doping is nonmagnetic, indicating a hole-induced nonmagnetic-ferromagnetic transition. The calculated conductivity of cyclicgraphdiyne with 1/8, 1/4 and 3/8 hole doping concentration is much higher than that without doping or with 1/2 hole doping. These results make cyclicgraphdiyne really attractive. By studying several carbon monolayers, we find that a perfect flat band may occur in the lattices with both separated or corner-connected triangular motifs with only including nearest-neighboring hopping of electrons, and the dispersion of flat band can be tuned by next-nearest-neighboring hopping. Our results shed insightful light on the formation of flat band in TBG. The present study also poses an alternative way to manipulate magnetism through doping flat band in carbon materials.

Plasmon spectrum of graphene monolayer on substrate

2019 ◽  
Vol 33 (09) ◽  
pp. 1950102
Author(s):  
I. N. Askerzade ◽  
R. T. Askerbeyli
Keyword(s):  
Substrate Material ◽  
Plasmon Mode ◽  
Monolayer Graphene ◽  
Graphene Monolayer ◽  
Multilayer Graphene ◽  
Linear Dispersion ◽  
Long Wavelength ◽  
Theoretical Considerations ◽  
Plasmon Spectrum ◽  
Good Agreement

Plasmon modes in monolayer graphene on substrate are analyzed taking into account the thickness of graphene and substrate material layer in the evaluation of Coulomb potential. It is shown that plasmon mode in graphene monolayer has linear dispersion in contrast to multilayer graphene in long-wavelength limit. The slope of plasmon spectrum is determined by the thickness and dielectric constant of substrate. Obtained results are in good agreement with experimental data and other theoretical considerations.

scholarly journals Investigating the Integrity of Graphene towards the Electrochemical Hydrogen Evolution Reaction (HER)

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Alejandro García-Miranda Ferrari ◽  
Dale A. C. Brownson ◽  
Craig E. Banks
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Plane Surface ◽  
Linear Sweep Voltammetry ◽  
Monolayer Graphene ◽  
Multilayer Graphene ◽  
Linear Sweep ◽  
Electrochemical Reversibility ◽  
Physicochemical Characterisation ◽  
Few Layer Graphene

Abstract Mono-, few-, and multilayer graphene is explored towards the electrochemical Hydrogen Evolution Reaction (HER). Careful physicochemical characterisation is undertaken during electrochemical perturbation revealing that the integrity of graphene is structurally compromised. Electrochemical perturbation, in the form of electrochemical potential scanning (linear sweep voltammetry), as induced when exploring the HER using monolayer graphene, creates defects upon the basal plane surface that increases the coverage of edge plane sites/defects resulting in an increase in the electrochemical reversibility of the HER process. This process of improved HER performance occurs up to a threshold, where substantial break-up of the basal sheet occurs, after which the electrochemical response decreases; this is due to the destruction of the sheet integrity and lack of electrical conductive pathways. Importantly, the severity of these changes is structurally dependent on the graphene variant utilised. This work indicates that multilayer graphene has more potential as an electrochemical platform for the HER, rather than that of mono- and few-layer graphene. There is huge potential for this knowledge to be usefully exploited within the energy sector and beyond.

scholarly journals Multi-layer graphene as a selective detector for future lung cancer biosensing platforms

Nanoscale ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 2476-2483 ◽  
Author(s):  
E. Kovalska ◽  
P. Lesongeur ◽  
B. T. Hogan ◽  
A. Baldycheva
Keyword(s):  
Lung Cancer ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Surface Patterning ◽  
Multilayer Graphene ◽  
Layer Graphene ◽  
Selective Detector ◽  
Volatile Organic ◽  
Enhanced Selectivity

Multilayer graphene can be used to detect volatile organic compounds, with enhanced selectivity and sensitivity through surface patterning.

Optimization of fluid characteristics of 2D materials for inkjet printing

MRS Advances ◽  
2016 ◽  
Vol 1 (30) ◽  
pp. 2199-2206 ◽  
Author(s):  
Monica Michel ◽  
Jay A. Desai ◽  
Alberto Delgado ◽  
Chandan Biswas ◽  
Anupama B. Kaul
Keyword(s):  
Surface Energy ◽  
Inkjet Printing ◽  
Ethyl Cellulose ◽  
2D Materials ◽  
The Novel ◽  
Liquid Exfoliation ◽  
Drop Dynamics ◽  
Surface Energies ◽  
Fluid Characteristics

ABSTRACT2D materials have shown to be the next step in semiconductor use and device manufacturing that can allow us to reduce the size of most electronics. One of the novel ways to obtain 2D materials is through liquid exfoliation, in which these materials can be obtained by dispersing the smallest possible particles in different solvents. Once obtained, the solutions can be used to manufacture devices via different processes, one of which is inkjet printing. This process relies in selecting “jettable” fluids, which need to have the necessary combination of viscosity and surface energy or “wettability”. In this work we have modified the viscosities and surface energies of five solvents: IPA (Isopropanol), NMP (N-methyl – 2 pyrrolidone), DMA (Dimethylacetamide), DMF (Dimethylformamide) and a mixture of Cyclohexanone / Terpineol 7:3. We have found an avenue to tailor the viscosity of these solvents though the addition of Ethyl Cellulose (EC), where the viscosity has been increased by up to 15 times at an EC concentration of 6%. For inkjet printing, ideally a viscosity of 4 – 10 cP is recommended, which we have been able to achieve with all of the solvents studied. It has been found that the different solvents present different susceptibilities to the EC addition, with DMA and DMF being the least sensitive to the EC addition. We have also studied the change in the drop dynamics and interactions of the 2D solutions with the substrate. Through this analysis we have found solvents that appear to be attractive for inkjet printing of MoS2 and graphite.

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