The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Janina Maultzsch - One of the best experts on this subject based on the ideXlab platform.
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Phonon Dispersion in mos 2
Physical Review B, 2019Co-Authors: Hans Tornatzky, Roland Gillen, Hiroshi Uchiyama, Janina MaultzschAbstract:The Phonon Dispersion is one of the most fundamental properties of a crystalline material. It determines virtually all of its physical properties, including optical, electronic, mechanical, and thermal behavior. Despite its importance, the Phonon Dispersion of MoS${}_{2}$ -- one of the most investigated two-dimensional semiconductors -- has not been determined experimentally in relevant parts of the Brillouin zone. In a combined experimental and theoretical approach, the authors present comprehensively the entire Phonon Dispersion of a MoS${}_{2}$ crystal and determine displacement patterns, symmetries, and scattering intensities.
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signature of the two dimensional Phonon Dispersion in graphene probed by double resonant raman scattering
Physical Review B, 2013Co-Authors: Patrick May, Michele Lazzeri, Francesco Mauri, J S Reparaz, P Venezuela, Felix Herziger, Gordon Callsen, A Hoffmann, Janina MaultzschAbstract:In this article we unravel the origin of the two-Phonon D + D �� peak and its asymmetric line shape by combining experimental data of single-layer graphene with a full twodimensional calculation of the double-resonant Raman process based on fourth-order perturbation theory. We show that the main peak originates from Phonons along the K highsymmetry line and that the asymmetry is due to Phonons from the two-dimensional Brillouin zone. The analysis of the asymmetric line shape in experiment provides a direct probe of the two-dimensional Phonon Dispersion. We further show how the D + D �� peak evolves with the number of graphene layers.
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Phonon Dispersion of graphite by inelastic x ray scattering
Physical Review B, 2007Co-Authors: M Moh, Janina Maultzsch, E Dobardzic, Stephanie Reich, I Milosevic, M Damnjanovic, Alexey Osak, M Krisch, C ThomseAbstract:We present the full in-plane Phonon Dispersion of graphite obtained from inelastic x-ray scattering, including the optical and acoustic branches, as well as the mid-frequency range between the $K$ and $M$ points in the Brillouin zone, where experimental data have been unavailable so far. The existence of a Kohn anomaly at the $K$ point is further supported. We fit a fifth-nearest neighbour force-constants model to the experimental data, making improved force-constants calculations of the Phonon Dispersion in both graphite and carbon nanotubes available.
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Phonon Dispersion of graphite by inelastic x ray scattering
Physical Review B, 2007Co-Authors: Marcel Mohr, Janina Maultzsch, E Dobardzic, Stephanie Reich, I Milosevic, M Damnjanovic, M Krisch, Alexey Bosak, C ThomsenAbstract:We present the full in-plane Phonon Dispersion of graphite obtained from inelastic x-ray scattering, including the optical and acoustic branches, as well as the midfrequency range between the $K$ and $M$ points in the Brillouin zone, where the experimental data have been unavailable so far. The existence of a Kohn anomaly at the $K$ point is further supported. We fit a fifth-nearest neighbor force-constant model to the experimental data, making improved force-constant calculations of the Phonon Dispersion in both graphite and carbon nanotubes available.
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double resonant raman scattering in graphite interference effects selection rules and Phonon Dispersion
Physical Review B, 2004Co-Authors: Janina Maultzsch, Stephanie Reich, C ThomseAbstract:We present a comprehensive analysis of double-resonant Raman scattering in graphite and derive an analytical expression for the Raman cross section of the D mode in one dimension. The extension to two dimensions does not change the double-resonant Phonon wave vectors. In the full integration of the Raman cross section, the contributions by Phonons from exactly the K point cancel due to destructive interference. We calculate the D mode explicitly based on recent experimental data of the graphite Phonon Dispersion. Applying the selection rules, a mapping of additional disorder-induced and second-order Raman modes onto the Brillouin zone of graphite is obtained. DOI: 10.1103/PhysRevB.70.155403
Ado Jorio - One of the best experts on this subject based on the ideXlab platform.
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raman scattering study of the Phonon Dispersion in twisted bilayer graphene
Nano Research, 2013Co-Authors: Jessica Camposdelgado, Ado Jorio, Luiz Gustavo Cancado, C A Achete, Jeanpierre RaskinAbstract:Bilayer graphene with a twist angle θ between the layers generates a superlattice structure known as a Moire pattern. This superlattice provides a θ-dependent q wavevector that activates Phonons in the interior of the Brillouin zone. Here we show that this superlattice-induced Raman scattering can be used to probe the Phonon Dispersion in twisted bilayer graphene (tBLG). The effect reported here is different from the widely studied double-resonance in graphene-related materials in many aspects, and despite the absence of stacking order in tBLG, layer breathing vibrations (namely ZO’ Phonons) are observed.
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raman scattering study of the Phonon Dispersion in twisted bilayer graphene
Nano Research, 2013Co-Authors: Jessica Camposdelgado, Ado Jorio, Luiz Gustavo Cancado, C A Achete, Jeanpierre RaskiAbstract:Bilayer graphene with a twist angle θ between the layers generates a superlattice structure known as a Moire pattern. This superlattice provides a θ-dependent q wavevector that activates Phonons in the interior of the Brillouin zone. Here we show that this superlattice-induced Raman scattering can be used to probe the Phonon Dispersion in twisted bilayer graphene (tBLG). The effect reported here is different from the widely studied double-resonance in graphene-related materials in many aspects, and despite the absence of stacking order in tBLG, layer breathing vibrations (namely ZO’ Phonons) are observed. Open image in new window
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determination of two dimensional Phonon Dispersion relation of graphite by raman spectroscopy
Physical Review B, 2002Co-Authors: A Gruneis, Riichiro Saito, Ado Jorio, A Souza G Filho, M A Pimenta, T Kimura, Luiz Gustavo Cancado, G DresselhausAbstract:Phonon Dispersion relations of a two-dimensional (2D) graphite are obtained by fitting dispersive Raman modes that originate from nonzone center Phonons near the $\ensuremath{\Gamma}$ or K point in the Brillouin zone (BZ). A new set of 12 force constants of 2D graphite up to the fourth neighbor are determined by a self-consistent fitting procedure, combined with double-resonance Raman theory. Analytical expressions for eigenvalues and eigenvectors at high symmetry points of the BZ are presented.
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probing Phonon Dispersion relations of graphite by double resonance raman scattering
Physical Review Letters, 2001Co-Authors: Riichiro Saito, Mildred S. Dresselhaus, Ado Jorio, A Souza G Filho, G Dresselhaus, M A PimentaAbstract:The Phonon Dispersion relations of graphite can be probed over a wide range of the Brillouin zone by double resonance Raman spectroscopy. The double resonance Raman process provides us with new assignments for the dispersive and nondispersive features observed in the Raman spectra of disordered graphite and carbon nanotubes, some features having been incorrectly assigned previously, or not assigned at all.
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probing Phonon Dispersion relations of graphite by double resonance raman scattering
Physical Review Letters, 2001Co-Authors: Riichiro Saito, Mildred S. Dresselhaus, Ado Jorio, A Souza G Filho, G Dresselhaus, M A PimentaAbstract:(Received 13 August 2001; published 20 December 2001)The Phonon Dispersion relations of graphite can be probed over a wide range of the Brillouin zoneby double resonance Raman spectroscopy. The double resonance Raman process provides us with newassignments for the dispersive and nondispersive features observed in the Raman spectra of disorderedgraphite and carbon nanotubes, some features having been incorrectly assigned previously, or not as-signed at all.
M A Pimenta - One of the best experts on this subject based on the ideXlab platform.
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determination of la and to Phonon Dispersion relations of graphene near the dirac point by double resonance raman scattering
Physical Review B, 2007Co-Authors: D L Mafra, Ge G Samsonidze, Leandro M Malard, D C Elias, J C A, F Plentz, E S Alves, M A PimentaAbstract:Raman spectroscopy was used to determine the Dispersion of the longitudinal acoustic (LA) and in-plane transverse optic Phonon branches near the Dirac $K$ point of monolayer graphene from the analysis of the Dispersion of two second-order Raman peaks involving the LA and TO Phonons. We show that the velocities of the Phonons involved in the double resonance Raman process are given by ${v}_{\mathit{LA}}=7.70\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}{v}_{F}$ and ${v}_{\mathit{TO}}=5.47\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}{v}_{F}$, where ${v}_{F}$ is the Fermi velocity of the associated electrons. The experimental results for the Phonon Dispersion in monolayer graphene are compared with those for turbostratic graphite and also with different theoretical models.
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determination of two dimensional Phonon Dispersion relation of graphite by raman spectroscopy
Physical Review B, 2002Co-Authors: A Gruneis, Riichiro Saito, Ado Jorio, A Souza G Filho, M A Pimenta, T Kimura, Luiz Gustavo Cancado, G DresselhausAbstract:Phonon Dispersion relations of a two-dimensional (2D) graphite are obtained by fitting dispersive Raman modes that originate from nonzone center Phonons near the $\ensuremath{\Gamma}$ or K point in the Brillouin zone (BZ). A new set of 12 force constants of 2D graphite up to the fourth neighbor are determined by a self-consistent fitting procedure, combined with double-resonance Raman theory. Analytical expressions for eigenvalues and eigenvectors at high symmetry points of the BZ are presented.
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probing Phonon Dispersion relations of graphite by double resonance raman scattering
Physical Review Letters, 2001Co-Authors: Riichiro Saito, Mildred S. Dresselhaus, Ado Jorio, A Souza G Filho, G Dresselhaus, M A PimentaAbstract:The Phonon Dispersion relations of graphite can be probed over a wide range of the Brillouin zone by double resonance Raman spectroscopy. The double resonance Raman process provides us with new assignments for the dispersive and nondispersive features observed in the Raman spectra of disordered graphite and carbon nanotubes, some features having been incorrectly assigned previously, or not assigned at all.
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probing Phonon Dispersion relations of graphite by double resonance raman scattering
Physical Review Letters, 2001Co-Authors: Riichiro Saito, Mildred S. Dresselhaus, Ado Jorio, A Souza G Filho, G Dresselhaus, M A PimentaAbstract:(Received 13 August 2001; published 20 December 2001)The Phonon Dispersion relations of graphite can be probed over a wide range of the Brillouin zoneby double resonance Raman spectroscopy. The double resonance Raman process provides us with newassignments for the dispersive and nondispersive features observed in the Raman spectra of disorderedgraphite and carbon nanotubes, some features having been incorrectly assigned previously, or not as-signed at all.
A Souza G Filho - One of the best experts on this subject based on the ideXlab platform.
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determination of two dimensional Phonon Dispersion relation of graphite by raman spectroscopy
Physical Review B, 2002Co-Authors: A Gruneis, Riichiro Saito, Ado Jorio, A Souza G Filho, M A Pimenta, T Kimura, Luiz Gustavo Cancado, G DresselhausAbstract:Phonon Dispersion relations of a two-dimensional (2D) graphite are obtained by fitting dispersive Raman modes that originate from nonzone center Phonons near the $\ensuremath{\Gamma}$ or K point in the Brillouin zone (BZ). A new set of 12 force constants of 2D graphite up to the fourth neighbor are determined by a self-consistent fitting procedure, combined with double-resonance Raman theory. Analytical expressions for eigenvalues and eigenvectors at high symmetry points of the BZ are presented.
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probing Phonon Dispersion relations of graphite by double resonance raman scattering
Physical Review Letters, 2001Co-Authors: Riichiro Saito, Mildred S. Dresselhaus, Ado Jorio, A Souza G Filho, G Dresselhaus, M A PimentaAbstract:The Phonon Dispersion relations of graphite can be probed over a wide range of the Brillouin zone by double resonance Raman spectroscopy. The double resonance Raman process provides us with new assignments for the dispersive and nondispersive features observed in the Raman spectra of disordered graphite and carbon nanotubes, some features having been incorrectly assigned previously, or not assigned at all.
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probing Phonon Dispersion relations of graphite by double resonance raman scattering
Physical Review Letters, 2001Co-Authors: Riichiro Saito, Mildred S. Dresselhaus, Ado Jorio, A Souza G Filho, G Dresselhaus, M A PimentaAbstract:(Received 13 August 2001; published 20 December 2001)The Phonon Dispersion relations of graphite can be probed over a wide range of the Brillouin zoneby double resonance Raman spectroscopy. The double resonance Raman process provides us with newassignments for the dispersive and nondispersive features observed in the Raman spectra of disorderedgraphite and carbon nanotubes, some features having been incorrectly assigned previously, or not as-signed at all.
Francesco Mauri - One of the best experts on this subject based on the ideXlab platform.
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signature of the two dimensional Phonon Dispersion in graphene probed by double resonant raman scattering
Physical Review B, 2013Co-Authors: Patrick May, Michele Lazzeri, Francesco Mauri, J S Reparaz, P Venezuela, Felix Herziger, Gordon Callsen, A Hoffmann, Janina MaultzschAbstract:In this article we unravel the origin of the two-Phonon D + D �� peak and its asymmetric line shape by combining experimental data of single-layer graphene with a full twodimensional calculation of the double-resonant Raman process based on fourth-order perturbation theory. We show that the main peak originates from Phonons along the K highsymmetry line and that the asymmetry is due to Phonons from the two-dimensional Brillouin zone. The analysis of the asymmetric line shape in experiment provides a direct probe of the two-dimensional Phonon Dispersion. We further show how the D + D �� peak evolves with the number of graphene layers.
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adiabatic and nonadiabatic Phonon Dispersion in a wannier function approach
Physical Review B, 2010Co-Authors: Matteo Calandra, Gianni Profeta, Francesco MauriAbstract:We develop a first-principles scheme to calculate adiabatic and nonadiabatic Phonon frequencies in the full Brillouin zone. The method relies on the stationary properties of a force-constant functional with respect to the first-order perturbation of the electronic charge density and on the localization of the deformation potential in the Wannier function basis. This allows for calculation of Phonon-Dispersion curves free from convergence issues related to Brillouin-zone sampling. In addition our approach justifies the use of the static screened potential in the calculation of the Phonon linewidth due to decay in electron-hole pairs. We apply the method to the calculation of the Phonon Dispersion and electron-Phonon coupling in ${\text{MgB}}_{2}$ and ${\text{CaC}}_{6}$. In both compounds we demonstrate the occurrence of several Kohn anomalies, absent in previous calculations, that are manifest only after careful electron- and Phonon-momentum integration. In ${\text{MgB}}_{2}$, the presence of Kohn anomalies on the ${\text{E}}_{2g}$ branches improves the agreement with measured Phonon spectra and affects the position of the main peak in the Eliashberg function. In ${\text{CaC}}_{6}$ we show that the nonadiabatic effects on in-plane carbon vibrations are not localized at zone center but are sizable throughout the full Brillouin zone. Our method opens perspectives in large-scale first-principles calculations of dynamical properties and electron-Phonon interaction.
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Adiabatic and nonadiabatic Phonon Dispersion in a Wannier function approach
Physical Review B: Condensed Matter and Materials Physics, 2010Co-Authors: Matteo Calandra, Gianni Profeta, Francesco MauriAbstract:We develop a first-principles scheme to calculate adiabatic and nonadiabatic Phonon frequencies in the full Brillouin zone. The method relies on the stationary properties of a force-constant functional with respect to the first-order perturbation of the electronic charge density and on the localization of the deformation potential in the Wannier function basis. This allows for calculation of Phonon-Dispersion curves free from convergence issues related to Brillouin-zone sampling. In addition our approach justifies the use of the static screened potential in the calculation of the Phonon linewidth due to decay in electron-hole pairs. We apply the method to the calculation of the Phonon Dispersion and electron-Phonon coupling in MgB2 and CaC6. In both compounds we demonstrate the occurrence of several Kohn anomalies, absent in previous calculations, that are manifest only after careful electron- and Phonon-momentum integration. In MgB2, the presence of Kohn anomalies on the E2g branches improves the agreement with measured Phonon spectra and affects the position of the main peak in the Eliashberg function. In CaC6 we show that the nonadiabatic effects on in-plane carbon vibrations are not localized at zone center but are sizable throughout the full Brillouin zone. Our method opens perspectives in large-scale first-principles calculations of dynamical properties and electron-Phonon interacti
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Phonon Dispersion and lifetimes in MgB2
Physical Review Letters, 2003Co-Authors: Abhay Shukla, Matteo Calandra, Matteo D'astuto, Michele Lazzeri, Francesco Mauri, Christophe Bellin, Michael Krisch, J. Karpinski, S. M. Kazakov, J. JunAbstract:We measure Phonon Dispersion and linewidth in a single crystal of MgB_2 along the Gamma-A, Gamma-M and A-L directions using inelastic X-Ray scattering. We use Density Functional Theory to compute the effect of both electron-Phonon coupling and anharmonicity on the linewidth, obtaining excellent agreement with experiment. Anomalous broadening of the E_2g Phonon mode is found all along Gamma-A. The dominant contribution to the linewidth is always the electron-Phonon coupling.