Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

The rise of graphene

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

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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The electronic properties of graphene

Quantum electrodynamics (resulting from the merger of quantum mechanics and relativity theory) has provided a clear understanding of phenomena ranging from particle physics to cosmology and from astrophysics to quantum chemistry. The ideas underlying quantum electrodynamics also influence the theory of condensed matter, but quantum relativistic effects are usually minute in the known experimental systems that can be described accurately by the non-relativistic Schrodinger equation. Here we report an experimental study of a condensed-matter system (graphene, a single atomic layer of carbon) in which electron transport is essentially governed by Dirac's (relativistic) equation. The charge carriers in graphene mimic relativistic particles with zero rest mass and have an effective 'speed of light' c* approximately 10(6) m s(-1). Our study reveals a variety of unusual phenomena that are characteristic of two-dimensional Dirac fermions. In particular we have observed the following: first, graphene's conductivity never falls below a minimum value corresponding to the quantum unit of conductance, even when concentrations of charge carriers tend to zero; second, the integer quantum Hall effect in graphene is anomalous in that it occurs at half-integer filling factors; and third, the cyclotron mass m(c) of massless carriers in graphene is described by E = m(c)c*2. This two-dimensional system is not only interesting in itself but also allows access to the subtle and rich physics of quantum electrodynamics in a bench-top experiment.

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Two-dimensional gas of massless Dirac fermions in graphene

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

We have experimentally demonstrated blackbodylike behavior in a thin nanostructured metallic layer shaped in the form of a composite deep diffraction grating. This behavior is recorded over a wide optical wavelength range (240--550 nm) and for a broad range of angles of light incidence $(0--75\ifmmode^\circ\else\textdegree\fi{})$ for samples with metal thickness of just 90 nm. The strong absorption at a level of 97--99% is observed for one light polarization and is attributed to excitation of localized plasmons coupled to incident light waves. We show that the studied structures exhibit anomalies which consist in disappearance of reflection for both $p$- and $s$-polarized light at corresponding ``Brewster'' angles. An effective-medium approach provides a satisfactory qualitative description of the reflection and transmission spectra in our samples and confirms their blackbody behavior.

Plasmonic blackbody : Almost complete absorption of light in nanostructured metallic coatings

We characterize plasmonic enhancement in a hotspot between two Au nanodisks using Raman scattering of graphene. Single layer graphene is suspended across the dimer cavity and provides an ideal two-dimensional test material for the local near-field distribution. We detect a Raman enhancement of the order of 103 originating from the cavity. Spatially resolved Raman measurements reveal a near-field localization one order of magnitude smaller than the wavelength of the excitation, which can be turned off by rotating the polarization of the excitation. The suspended graphene is under tensile strain. The resulting phonon mode softening allows for a clear identification of the enhanced signal compared to unperturbed graphene.

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Polarized Plasmonic Enhancement by Au Nanostructures Probed through Raman Scattering of Suspended Graphene

We fabricate gold plasmonic nanoarrays on a glass substrate supporting narrow collective (diffraction coupled) resonances that can be excited with normal incident light in an asymmetric air or water environment. We measure quality factors of normal incidence resonances up to 19 in air, 45 in water, and 85 in glycerol and register a very high figure of merit for biosensing applications in water. The coupled dipole approximation is used to evaluate the optimum resonance conditions and qualitatively explain the properties of the resonances. Our results could help to develop simpler and cheaper surface plasmon resonance based approaches to gas and biodetection.

Narrow Collective Plasmon Resonances in Nanostructure Arrays Observed at Normal Light Incidence for Simplified Sensing in Asymmetric Air and Water Environments

We report properties of a plasmonic nanoarray coupled to a single layered graphene sheet transferred on the top of the nanoarray. We observe significant (up to 1000 times) enhancements of resonant Raman scattering from a graphene layer generated by near fields of a plasmonic nanoarray. This enhancement is quantitatively explained by the electromagnetic mechanism. We experimentally demonstrate a significant spectral shift of diffractive coupled plasmon resonances induced by the graphene presence and show that the collective plasmon resonances can be used to study surface chemistry of graphene. Our results emphasize prospective capabilities of graphene-functionalized plasmonics.

Surface Hydrogenation and Optics of a Graphene Sheet Transferred onto a Plasmonic Nanoarray

The composition and magnetic properties of two types of ultrathin ${\mathrm{Fe}}_{3\ensuremath{-}\ensuremath{\delta}}{\mathrm{O}}_{4}(111)$ films grown epitaxially on Pt(111) have been characterized using conversion electron M\"ossbauer spectroscopy (CEMS) and x-ray magnetic circular dichroism (XMCD). CEMS data from both films indicate that the magnetic moments lie in-plane and that a paramagnetic contribution is present that is not seen in spectra of bulk magnetite samples. The XMCD results are in good agreement with theoretical calculations, enabling the stoichiometry of the films to be determined as ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ and ${\mathrm{Fe}}_{2.91}{\mathrm{O}}_{4}.$ The concentrations of both the tetrahedral ${\mathrm{Fe}}^{3+}$ and octahedral ${\mathrm{Fe}}^{2+}$ ions are reduced in the nonstoichiometric film, the decrease in the tetrahedral site probably being due to disorder. CEMS consistently yields a high tetrahedral:octahedral ratio of about 0.7:1, probably because of a contribution from a nonstoichiometric FeO interface layer.

Fred Schedin

Papers

Plasmonic blackbody : Almost complete absorption of light in nanostructured metallic coatings

Polarized Plasmonic Enhancement by Au Nanostructures Probed through Raman Scattering of Suspended Graphene

Narrow Collective Plasmon Resonances in Nanostructure Arrays Observed at Normal Light Incidence for Simplified Sensing in Asymmetric Air and Water Environments

Surface Hydrogenation and Optics of a Graphene Sheet Transferred onto a Plasmonic Nanoarray

Stoichiometry of Fe3-delta O4(111) ultrathin films on Pt(111)