Abstract:Gaussian deformation in graphene structures exhibits an interesting effect in which flowershaped confinement states are observed in the deformed region [Carrillo-Bastos et al., Phys. Rev. B 90 041411 (2014)]. To exploit such a deformation for various applications, tunable electronic features including a bandgap opening for semi-metallic structures are expected.Besides, the effects of disorders and external excitations also need to be considered. In this work, we present a systematic study on quantum transpor… Show more
“…Bumps are often observed in graphene samples and can be artificially induced, for example, by pinning graphene on patterned substrates [40,41] or by thermally inducing a buckling transition [42]. In the absence of magnetic field, such a system has been widely investigated in the literature [43][44][45][46][47], with focus on both electronic structure and transport properties in 2D graphene and graphene ribbons or dots. Here, we focus on the case of periodic bumps with a Gaussian profile similar to that of ref.…”
Hamiltonian models based on a localized basis set are widely used in condensed matter physics, as, for example, for the calculation of electronic structures or transport properties. The presence of a weak and homogeneous magnetic field can be taken into account through Peierls phase factors on the hopping Hamiltonian elements. Here, we propose simple and convenient recipes to properly determine such Peierls phase factors for quasi-one-dimensional systems that are periodic or with periodic subcomponents (as in Hall bars, for example), and periodic two-dimensional systems. We also show some examples of applications of the formulas, and more specifically concerning the electronic structure of carbon nanotubes in magnetic fields, the integer quantum Hall effect in six-terminal bars obtained in two-dimensional electron gases, and the electronic structure of bumped graphene superlattices in the presence of a magnetic field.
“…Bumps are often observed in graphene samples and can be artificially induced, for example, by pinning graphene on patterned substrates [40,41] or by thermally inducing a buckling transition [42]. In the absence of magnetic field, such a system has been widely investigated in the literature [43][44][45][46][47], with focus on both electronic structure and transport properties in 2D graphene and graphene ribbons or dots. Here, we focus on the case of periodic bumps with a Gaussian profile similar to that of ref.…”
Hamiltonian models based on a localized basis set are widely used in condensed matter physics, as, for example, for the calculation of electronic structures or transport properties. The presence of a weak and homogeneous magnetic field can be taken into account through Peierls phase factors on the hopping Hamiltonian elements. Here, we propose simple and convenient recipes to properly determine such Peierls phase factors for quasi-one-dimensional systems that are periodic or with periodic subcomponents (as in Hall bars, for example), and periodic two-dimensional systems. We also show some examples of applications of the formulas, and more specifically concerning the electronic structure of carbon nanotubes in magnetic fields, the integer quantum Hall effect in six-terminal bars obtained in two-dimensional electron gases, and the electronic structure of bumped graphene superlattices in the presence of a magnetic field.
“…Confining states within deformed GNR, symmetry properties of LDOS, conductance spectra and pseudospin polarization have been studied in the frame of TB approximation 18 . The effects of an external electric field, the influence of edge roughness on conduction properties of deformed GNRs with centrosymmetric Gaussian bump have been studied using TB model and NEGF transport formalism 19 . Figure 1 The schematic view of the armchair graphene nanoribbon system.…”
Section: Introductionmentioning
confidence: 99%
“…The necessary condition to achieve such a conductance property is the existence of sufficiently large energy gap and relatively high conductance outside the gap. We note that recent studies on electron transport properties of GNRs, focused on the energy gap opening mechanism 19 and valley filtering mechanism 6 , are limited to centrosymmetric Gaussian bumps or pure Gaussian folds. In particular, it has been shown that centrosymmetric Gaussian deformation strongly modifies the electronic properties of all types of ribbon structures and leads to a strong reduction of electron transmission in high-energy regions 19 .…”
Section: Introductionmentioning
confidence: 99%
“…We note that recent studies on electron transport properties of GNRs, focused on the energy gap opening mechanism 19 and valley filtering mechanism 6 , are limited to centrosymmetric Gaussian bumps or pure Gaussian folds. In particular, it has been shown that centrosymmetric Gaussian deformation strongly modifies the electronic properties of all types of ribbon structures and leads to a strong reduction of electron transmission in high-energy regions 19 . Investigations presented in this paper show that for the systems with comparable number of transmission modes as considered in the paper 19 , fundamental requirements related to transport properties (large transport gap and good conductance for higher energies) can be satisfied simultaneously for properly deformed GQD as an effect of geometric anisotropy, modeled by Gaussian deformation, of an elliptic type.…”
A theoretical investigation on electron transport properties of rectangular graphene quantum dots (GQDs) with non-centro-symmetric out-of-plane Gaussian deformation of elliptic type is presented. Different levels of deformation are explored to estimate system geometry optimal for potential electronic applications. Electronic properties of deformed GQDs are studied in terms of local density of states (LDOS), band-gap opening and equilibrium ballistic conductance. In particular, it was observed that the symmetry of spatial LDOS structure is directly linked with the symmetry of properly defined local strain field (LSF) map, for a wide energy range. The relationship confirms qualitatively predictions obtained on the basis of the concept of a pseudomagnetic field, used in continuum models of graphene, including strain induced effects. The conductance spectra of deformed GQD as a device connected to semi-infinite graphene armchair nanoribbons as reservoirs are studied in a frame of tight-binding (TB) model in combination with non-equilibrium Green’s-functions technique (NEGF).
“…At present, the method of converting coal into graphene is basically to change large-particle coal into a precursor carbon source before preparing graphene, and the precursor carbon source can be in the form of molecules, or gas. The preparation method of a precursor carbon source includes the preliminary screening of raw coal, impurity removal, pyrolysis (dry distillation), gasification and liquefaction of coal [ 7 , 8 ]. The usual preparation methods of graphene fabrication from precursor carbon sources include chemical synthesis, mechanical exfoliation, pyrolysis of silicon carbide and chemical vapor deposition [ 9 , 10 , 11 , 12 , 13 , 14 ].…”
Industrial preparation of graphene has been a research hotspot in recent years. Finding an economical and practical carbon source and reducing the cost of production and instrument is significant in industrial graphene production. Coal is a common carbon source. Efficient improvement and utilization in the cleaning of coal has recently been a popular research area. In this study, we developed a set of graphene preparation methods based on Anhui Huainan’s low-rank gas coal (HNGC). Using self-built experimental equipment, benzene precursor was prepared from HNGC and used as carbon source to realize graphene growth. The quality of the graphene was characterized by a high-resolution microscope and Raman spectrometer. This study provides a new idea and method for the preparation of low-rank coal-based graphene.
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