References of "Pichler, T"
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See detailPhonon surface mapping of graphite: Disentangling quasi-degenerate phonon dispersions
Grueneis, A.; Serrano, J.; Bosak, A. et al

in Physical Review B (2009), 80(8),

The two-dimensional mapping of the phonon dispersions around the K point of graphite by inelastic x-ray scattering is provided. The present work resolves the longstanding issue related to the correct ... [more ▼]

The two-dimensional mapping of the phonon dispersions around the K point of graphite by inelastic x-ray scattering is provided. The present work resolves the longstanding issue related to the correct assignment of transverse and longitudinal phonon branches at K. We observe an almost degeneracy of the three TO-, LA-, and LO-derived phonon branches and a strong phonon trigonal warping. Correlation effects renormalize the Kohn anomaly of the TO mode, which exhibits a trigonal warping effect opposite to that of the electronic band structure. We determined the electron-phonon coupling constant to be 166 (eV/A degrees)(2) in excellent agreement to GW calculations. These results are fundamental for understanding angle-resolved photoemission, double-resonance Raman and transport measurements of graphene-based systems. [less ▲]

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See detailTight-binding description of the quasiparticle dispersion of graphite and few-layer graphene
Grueneis, A.; Attaccalite, C.; Wirtz, Ludger UL et al

in Physical Review B (2008), 78(20),

A universal set of third-nearest-neighbor tight-binding (TB) parameters is presented for calculation of the quasiparticle (QP) dispersion of N stacked sp(2) graphene layers (N=1...infinity) with AB ... [more ▼]

A universal set of third-nearest-neighbor tight-binding (TB) parameters is presented for calculation of the quasiparticle (QP) dispersion of N stacked sp(2) graphene layers (N=1...infinity) with AB stacking sequence. The present TB parameters are fit to ab initio calculations on the GW level and are universal, allowing to describe the whole pi "experimental" band structure with one set of parameters. This is important for describing both low-energy electronic transport and high-energy optical properties of graphene layers. The QP bands are strongly renormalized by electron-electron interactions, which results in a 20% increase in the nearest-neighbor in-plane and out-of-plane TB parameters when compared to band structure from density-functional theory. With the new set of TB parameters we determine the Fermi surface and evaluate exciton energies, charge carrier plasmon frequencies, and the conductivities which are relevant for recent angle-resolved photoemission, optical, electron energy loss, and transport measurements. A comparision of these quantitities to experiments yields an excellent agreement. Furthermore we discuss the transition from few-layer graphene to graphite and a semimetal to metal transition in a TB framework. [less ▲]

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See detailElectron-electron correlation in graphite: A combined angle-resolved photoemission and first-principles study
Grueneis, A.; Attaccalite, C.; Pichler, T. et al

in Physical Review Letters (2008), 100(3), 037601

The full three-dimensional dispersion of the pi bands, Fermi velocities, and effective masses are measured with angle-resolved photoemission spectroscopy and compared to first-principles calculations. The ... [more ▼]

The full three-dimensional dispersion of the pi bands, Fermi velocities, and effective masses are measured with angle-resolved photoemission spectroscopy and compared to first-principles calculations. The band structure by density-functional theory underestimates the slope of the bands and the trigonal warping effect. Including electron-electron correlation on the level of the GW approximation, however, yields remarkable improvement in the vicinity of the Fermi level. This demonstrates the breakdown of the independent electron picture in semimetallic graphite and points toward a pronounced role of electron correlation for the interpretation of transport experiments and double-resonant Raman scattering for a wide range of carbon based materials. [less ▲]

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See detailLow energy quasiparticle dispersion of graphite by angle-resolved photoemission spectroscopy
Grueneis, A.; Pichler, T.; Shiozawa, H. et al

in PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS (2007), 244(11), 4129-4133

The low energy electron dispersion in graphite is measured by angle-resolved photoemission spectroscopy. The measured photoemission intensity maxima are compared to a tight-binding calculation of the ... [more ▼]

The low energy electron dispersion in graphite is measured by angle-resolved photoemission spectroscopy. The measured photoemission intensity maxima are compared to a tight-binding calculation of the electronic band structure. We observe a strong trigonal warping of the equi-energy contour which is well reproduced by the calculations. Furthermore we clearly show that the concept of Dirac Fermions breaks down for AB stacked graphite. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. [less ▲]

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See detailFormation and electronic properties of BC3 single-wall nanotubes upon boron substitution of carbon nanotubes
Fuentes, G. G.; Borowiak-Palen, E.; Knupfer, M. et al

in Physical Review B (2004), 69(24),

We report a detailed experimental and theoretical study on the electronic and optical properties of highly boron-substituted (up to 15 at.%) single-wall carbon nanotubes. Core-level electron energy-loss ... [more ▼]

We report a detailed experimental and theoretical study on the electronic and optical properties of highly boron-substituted (up to 15 at.%) single-wall carbon nanotubes. Core-level electron energy-loss spectroscopy reveals that the boron incorporates into the lattice structure of the tubes, transferring similar to1/2 hole per boron atom into the carbon derived unoccupied density of states. The charge transfer and the calculated Fermi-energy shift in the doped nanotubes evidence that a simple rigid-band model can be ruled out and that additional effects such as charge localization and doping induced band-structure changes play an important role at this high doping levels. In optical absorption a new peak appears at 0.4 eV which is independent of the doping level. Compared to the results from a series of ab initio calculations our results support the selective doping of semiconducting nanotubes and the formation of BC3 nanotubes instead of a homogeneous random boron substitution. [less ▲]

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See detailElectronic structure and optical properties of boron doped single-wall carbon nanotubes
Pichler, T.; Borowiak-Palen, E.; Fuentes, G. G. et al

in AIP Conference Proceedings (2003), 685

We present a study of the electronic structure and the optical properties of boron doped single walled carbon nanotubes which have been produced by a substitution reaction from nanotube templates. The ... [more ▼]

We present a study of the electronic structure and the optical properties of boron doped single walled carbon nanotubes which have been produced by a substitution reaction from nanotube templates. The morphology and crystal structure of the samples have been characterized by transmission electron microscopy and electron energy-loss spectroscopy. Clean boron doped SWCNT with an average boron content of 15 at% have been produced. The B1s and C1s core level spectra reveal that boron is in an sp(2) configuration and that the effective charge transfer is about 0.5 holes per boron to the C-derived states. The boron substitution also leads to new features in the optical absorption spectra which can be attributed to the appearance of an acceptor band about 0.1 eV above the top of the valence band of the SWCNT. These changes in the electronic structure and in the optical properties upon boron substitution are in good agreement with state of the art ab initio calculations. [less ▲]

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