The electronic properties of graphene
TL;DR: In this paper, the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations, are discussed.
Abstract: This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.
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TL;DR: This work reviews the historical development of Transition metal dichalcogenides, methods for preparing atomically thin layers, their electronic and optical properties, and prospects for future advances in electronics and optoelectronics.
Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.
13,348 citations
TL;DR: This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.
Abstract: Graphene is a wonder material with many superlatives to its name. It is the thinnest known material in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic mobility, have zero effective mass, and can travel for micrometers without scattering at room temperature. Graphene can sustain current densities six orders of magnitude higher than that of copper, shows record thermal conductivity and stiffness, is impermeable to gases, and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation, which allows the investigation of relativistic quantum phenomena in a benchtop experiment. This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.
12,117 citations
TL;DR: Topological superconductors are new states of quantum matter which cannot be adiabatically connected to conventional insulators and semiconductors and are characterized by a full insulating gap in the bulk and gapless edge or surface states which are protected by time reversal symmetry.
Abstract: Topological insulators are new states of quantum matter which cannot be adiabatically connected to conventional insulators and semiconductors. They are characterized by a full insulating gap in the bulk and gapless edge or surface states which are protected by time-reversal symmetry. These topological materials have been theoretically predicted and experimentally observed in a variety of systems, including HgTe quantum wells, BiSb alloys, and Bi2Te3 and Bi2Se3 crystals. Theoretical models, materials properties, and experimental results on two-dimensional and three-dimensional topological insulators are reviewed, and both the topological band theory and the topological field theory are discussed. Topological superconductors have a full pairing gap in the bulk and gapless surface states consisting of Majorana fermions. The theory of topological superconductors is reviewed, in close analogy to the theory of topological insulators.
11,092 citations
TL;DR: An overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.
Abstract: There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.
8,919 citations
TL;DR: This Review describes how the tunable electronic structure of TMDs makes them attractive for a variety of applications, as well as electrically active materials in opto-electronics.
Abstract: Ultrathin two-dimensional nanosheets of layered transition metal dichalcogenides (TMDs) are fundamentally and technologically intriguing. In contrast to the graphene sheet, they are chemically versatile. Mono- or few-layered TMDs - obtained either through exfoliation of bulk materials or bottom-up syntheses - are direct-gap semiconductors whose bandgap energy, as well as carrier type (n- or p-type), varies between compounds depending on their composition, structure and dimensionality. In this Review, we describe how the tunable electronic structure of TMDs makes them attractive for a variety of applications. They have been investigated as chemically active electrocatalysts for hydrogen evolution and hydrosulfurization, as well as electrically active materials in opto-electronics. Their morphologies and properties are also useful for energy storage applications such as electrodes for Li-ion batteries and supercapacitors.
7,903 citations
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TL;DR: In this paper, the effect of structural nanoconstriction on the coherent transport properties of infinitely long graphene ribbons was studied. But the results were limited to the case of a single atom being removed from the sample.
Abstract: We study the effect of a structural nanoconstriction on the coherent transport properties of otherwise ideal zigzag-edged infinitely long graphene ribbons. The electronic structure is calculated with the standard oneorbital tight-binding model and the linear conductance is obtained using the Landauer formula. We find that, since the zero-bias current is carried in the bulk of the ribbon, this is very robust with respect to a variety of constriction geometries and edge defects. In contrast, the curve of zero-bias conductance versus gate voltage departs from the 2n +1 e 2 /h staircase of the ideal case as soon as a single atom is removed from the sample. We also find that wedge-shaped constrictions can present nonconducting states fully localized in the constriction close to the Fermi energy. The interest of these localized states in regards to the formation of quantum dots in graphene is discussed.
161 citations
"The electronic properties of graphe..." refers background in this paper
...This implies that a pre ursorstru ture for lo alized states at the Dira energy anbe found in ribbons or onstri tions of small lengths(Muñoz-Rojas et al., 2006), whi h modi es the ele troni stru ture and transport properties....
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TL;DR: In this article, the charge distribution induced by external fields in finite stacks of graphene planes, or in semi-infinite graphite is considered, and the interlayer electronic hybridization is described by a nearest-neighbor hopping term.
Abstract: The charge distribution induced by external fields in finite stacks of graphene planes, or in semi-infinite graphite is considered. The interlayer electronic hybridization is described by a nearest-neighbor hopping term, and the charge induced by the self-consistent electrostatic potential is calculated within the linear response theory (random phase approximation). The screening properties are determined by contributions from interband and intraband electronic transitions. In neutral systems, only interband transitions contribute to the charge polarizability, leading to insulatinglike screening properties, and to oscillations in the induced charge, with a period equal to the interlayer spacing. In doped systems, we find a screening length that is equivalent to two-to-three graphene layers, superimposed to significant charge oscillations.
160 citations
"The electronic properties of graphe..." refers background in this paper
...The hopping leads to coherence (Guinea, 2007)....
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...The hopping leads to oheren e (Guinea, 2007)....
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...This effect greatly enhances Friedel like oscillations in the charge distribution in the out of plane direction, which can lead to the changes in the sign of the charge in neighboring layers (Guinea, 2007)....
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...Rev. Lett.100, 026802.Castro Neto, A. H., 2007, Nature Materials 6, 176.Castro Neto, A. H., and F. Guinea, 2007, Phys....
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...The renormalized phonon frequen y, Ω0(q), is givenby (Ando, 2006a, 2007b; Castro Neto and Guinea, 2007;Lazzeri and Mauri, 2006; Saha et al., 2007): Ω0(q) ≈ ω0 − 2β2 a2ω0 χ(q, ω0) , (209)where ω0 is the bare phonon frequen y, and the ele tron-phonon polarization fun tion is given by: χ(q, ω)=…...
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TL;DR: It is suggested that the ferromagnetism is a magnetic proximity effect induced at the interface with magnetite or kamacite inclusions, which is strongly ferromagnetic at room temperature.
Abstract: There are recent reports of weak ferromagnetism in graphite1,2 and synthetic carbon materials3 such as rhombohedral C60 (ref. 4), as well as a theoretical prediction of a ferromagnetic instability in graphene sheets5. With very small ferromagnetic signals, it is difficult to be certain that the origin is intrinsic, rather than due to minute concentrations of iron-rich impurities. Here we take a different experimental approach to study ferromagnetism in graphitic materials, by making use of meteoritic graphite, which is strongly ferromagnetic at room temperature. We examined ten samples of extraterrestrial graphite from a nodule in the Canyon Diablo meteorite. Graphite is the major phase in every sample, but there are minor amounts of magnetite, kamacite, akaganeite, and other phases. By analysing the phase composition of a series of samples, we find that these iron-rich minerals can only account for about two-thirds of the observed magnetization. The remainder is somehow associated with graphite, corresponding to an average magnetization of 0.05 Bohr magnetons per carbon atom. The magnetic ordering temperature is near 570 K. We suggest that the ferromagnetism is a magnetic proximity effect induced at the interface with magnetite or kamacite inclusions.
157 citations
"The electronic properties of graphe..." refers background in this paper
...Upon heating, the sili on from the top layersdesorbs, and a few layers of graphene are left onthe surfa e (Berger et al., 2004; Bommel et al., 1975;Coey et al., 2002; Forbeaux et al., 1998; Hass et al.,2007a; de Heer et al., 2007; Rollings et al., 2005)....
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TL;DR: In this article, it was demonstrated that the quasiparticle dynamics, the layer-dependent charge and potential, and the c-axis screening coefficient could be extracted from measurements of the spectral function of few layer graphene films grown epitaxially on SiC using angle-resolved photoemission spectroscopy (ARPES).
Abstract: Recently, it was demonstrated that the quasiparticle dynamics, the layer-dependent charge and potential, and the c-axis screening coefficient could be extracted from measurements of the spectral function of few layer graphene films grown epitaxially on SiC using angle-resolved photoemission spectroscopy (ARPES). In this paper we review these findings, and present detailed methodology for extracting such parameters from ARPES. We also present detailed arguments against the possibility of an energy gap at the Dirac crossing ED.
156 citations
TL;DR: In this article, the effects of simultaneous scattering from many scatterers on the level broadening of each Landau level are investigated by assuming short-ranged scatterrs, and the double-site approximation does not give physically reasonable solution of the self-consistency equation which determines the Green's function.
Abstract: Effects of simultaneous scattering from many scatterers on the level broadening of each Landau level are investigated by assuming short-ranged scatterers. The double-site approximation, which is the direct extension of the single-site approximation, does not give physically reasonable solution of the self-consistency equation which determines the Green's function. Such singular behavior is a result of the incorrect analyticity of the self-energy part and is shown to exist in still higher approximations. At high concentrations of scatterers, an approximate infinite summation of the many-site series gives a reasonable density of states, which has low- and high-energy tails and whose width is effectively smaller than that in the lowest approximation.
155 citations
"The electronic properties of graphe..." refers methods in this paper
...(Ando, 1974a,b, , 1975; Ando and Uemura, 1974; Ohta,1968, 1971) using the averaging pro edure over impuritypositions of Duke (Duke, 1968)....
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