D. M. Basko

Raman spectroscopy as a versatile tool for studying the properties of graphene

Raman spectroscopy is an integral part of graphene research. It is used to determine the number and orientation of layers, the quality and types of edge, and the effects of perturbations, such as electric and magnetic fields, strain, doping, disorder and functional groups. This, in turn, provides insight into all sp(2)-bonded carbon allotropes, because graphene is their fundamental building block. Here we review the state of the art, future directions and open questions in Raman spectroscopy of graphene. We describe essential physical processes whose importance has only recently been recognized, such as the various types of resonance at play, and the role of quantum interference. We update all basic concepts and notations, and propose a terminology that is able to describe any result in literature. We finally highlight the potential of Raman spectroscopy for layered materials other than graphene.

Graphene mode-locked ultrafast laser.

Graphene is at the center of a significant research effort. Near-ballistic transport at room temperature and high mobility make it a potential material for nanoelectronics. Its electronic and mechanical properties are also ideal for micro- and nanomechanical systems, thin-film transistors, and transparent and conductive composites and electrodes. Here we exploit the optoelectronic properties of graphene to realize an ultrafast laser. A graphene-polymer composite is fabricated using wet-chemistry techniques. Pauli blocking following intense illumination results in saturable absorption, independent of wavelength. This is used to passively mode-lock an erbium-doped fiber laser working at 1559 nm, with a 5.24 nm spectral bandwidth and approximately 460 fs pulse duration, paving the way to graphene-based photonics.

Raman Spectroscopy of Graphene Edges

Graphene edges are of particular interest since their orientation determines the electronic properties. Here we present a detailed Raman investigation of graphene flakes with edges oriented at different crystallographic directions. We also develop a real space theory for Raman scattering to analyze the general case of disordered edges. The position, width, and intensity of G and D peaks are studied as a function of the incident light polarization. The D-band is strongest for polarization parallel to the edge and minimum for perpendicular. Raman mapping shows that the D peak is localized in proximity of the edge. For ideal edges, the D peak is zero for zigzag orientation and large for armchair, allowing in principle the use of Raman spectroscopy as a sensitive tool for edge orientation. However, for real samples, the D to G ratio does not always show a significant dependence on edge orientation. Thus, even though edges can appear macroscopically smooth and oriented at well-defined angles, they are not necessarily microscopically ordered.

Metal-insulator transition in a weakly interacting many-electron system with localized single-particle states

Abstract We consider low-temperature behavior of weakly interacting electrons in disordered conductors in the regime when all single-particle eigenstates are localized by the quenched disorder. We prove that in the absence of coupling of the electrons to any external bath dc electrical conductivity exactly vanishes as long as the temperature T does not exceed some finite value Tc. At the same time, it can be also proven that at high enough T the conductivity is finite. These two statements imply that the system undergoes a finite temperature metal-to-insulator transition, which can be viewed as Anderson-like localization of many-body wave functions in the Fock space. Metallic and insulating states are not different from each other by any spatial or discrete symmetries. We formulate the effective Hamiltonian description of the system at low energies (of the order of the level spacing in the single-particle localization volume). In the metallic phase quantum Boltzmann equation is valid, allowing to find the kinetic coefficients. In the insulating phase, T

Electron-electron interactions and doping dependence of the two-phonon Raman intensity in graphene

Raman spectroscopy is a fast and nondestructive means to characterize graphene samples. In particular, the Raman spectra are strongly affected by doping. While the resulting change in position and width of the

Theory of resonant multiphonon Raman scattering in graphene

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Excitons and optical nonlinearities in hybrid organic-inorganic nanostructures

peak can be explained by the nonadiabatic Kohn anomaly at

Observation of three-dimensional massless Kane fermions in a zinc-blende crystal

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A Photothermoelectric Effect in Graphene

, the significant doping dependence of the

Weak chaos in the disordered nonlinear Schrödinger chain: Destruction of Anderson localization by Arnold diffusion

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