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

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/pssb.201290031

Front Cover: All‐optical structure assignment of individual single‐walled carbon nanotubes from Rayleigh and Raman scattering measurements (Phys. Status Solidi B 12/2012)

We perform infrared studies of the Landau level (LL) transitions in monolayer graphene in magnetic fields up to B = 18T. We observe both intra‐band transitions between neighboring hole/electron LLs, as well as inter‐band transitions between hole and electron LLs, all proportional to √B in energy. The lack of precise scaling between different LL transitions and the unexpectedly large energy shifts as a function of the LL filling factor near the charge neutrality point suggest considerable contributions of many‐body effects to the infrared transition energies.

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Cyclotron Resonance near the Charge Neutrality Point of Graphene


 The temperature distribution of current-carrying carbon nanotubes (CNs) have been measured by scanning thermal microscopy. The thermal imaging results support that multiwall (MW) CNs and semiconducting single wall (SW) CNs are diffusive and dissipative, while metallic SWCNs change from non dissipative at low electric fields to dissipative at high fields due to optical phonon emission. The temperature rise in a 4.5 μm long MWCN was of order 40 K for a power input of 22 μW and increased linearly with power input. There existed a large temperature drop at the tube-substrate interface due to a weak contact thermal conductance about 0.1 W/m-K. For the MWCN, comparable amount of Joule heat was lost from the tube bulk to the substrate and from the tube to the metal contacts.

Scanning Thermal Microscopy Study of Dissipation in Current-Carrying Carbon Nanotubes

Twisted interfaces between stacked van der Waals cuprate crystals enable tunable Josephson coupling between in-plane anisotropic superconducting order parameters. Employing a novel cryogenic assembly technique, we fabricate Josephson junctions with an atomically sharp twisted interface between Bi2Sr2CaCu2O8+x crystals. The Josephson critical current density sensitively depends on the twist angle, reaching the maximum value comparable to that of the intrinsic junctions at small twisting angles, and is suppressed by almost 2 orders of magnitude yet remains finite close to 45 degree twist angle. Through the observation of fractional Shapiro steps and the analysis of Fraunhofer patterns we show that the remaining superconducting coherence near 45 degree is due to the co-tunneling of Cooper pairs, a necessary ingredient for high-temperature topological superconductivity.

Emergent Interfacial Superconductivity between Twisted Cuprate Superconductors

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Philip Kim

Papers

Front Cover: All‐optical structure assignment of individual single‐walled carbon nanotubes from Rayleigh and Raman scattering measurements (Phys. Status Solidi B 12/2012)

Cyclotron Resonance near the Charge Neutrality Point of Graphene

Scanning Thermal Microscopy Study of Dissipation in Current-Carrying Carbon Nanotubes

Emergent Interfacial Superconductivity between Twisted Cuprate Superconductors

Effect of electron-electron interactions in thermoelectric power in graphene