Low-frequency excitation spectra in double-walled armchair carbon nanotubes

Ho, Yen-Hung; Ho, Ghim Wei; Chen, S. C.; Ho, J. H.; Lin, Mingyao

doi:10.1103/physrevb.76.115422

Cited by 12 publications

(20 citation statements)

References 39 publications

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“…4,[37][38][39] Even for some commensurate cases, such as armchair doublewall nanotubes with significant interwall hoppings, their contributions to the polarization function have been shown to be quite small in tight-binding calculations. 45 The polarization function P j (m,q) of tube j can be divided into two contributions,…”

Section: Formulationmentioning

confidence: 99%

Interwall screening and excitons in double-wall carbon nanotubes

2012

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Exciton properties of double-wall carbon nanotubes are studied in the static screened Hartree-Fock approximation within a k · p scheme. The intrawall electron-hole interaction is largely suppressed by interwall screening effects. The suppression is sensitive to the effective interwall distance between the inner and outer tubes and reduces the exciton binding energy as well as the band gap. As a result, the exciton energy levels are redshifted from those in the single-wall tube with the same diameter. The energy shift of the ground exciton has little dependence on the tube diameter, in contrast to that of the excited excitons. In the case of a metallic outer and inner tube, excited exciton states in the semiconducting tube disappear due to strong screening.

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Section: Formulationmentioning

confidence: 99%

Interwall screening and excitons in double-wall carbon nanotubes

2012

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“…This correspondence is as a consequence of the fact that the K and K points are related to each other via the time-reversal operation. 49,50 The Fourier transform of the Coulomb interaction, with angular momentum m along the circumference and wave number q in the axis direction is given by [51][52][53][54][55][56] …”

Section: Formulationmentioning

confidence: 99%

Cross-polarized excitons in double-wall carbon nanotubes

2012

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Optical absorption in double-wall carbon nanotubes for light polarized perpendicular to the tube axis is studied by taking into account exciton effects and depolarization effects within an effective-mass theory. The Coulomb interaction is suppressed by not only intrawall screening effects but also interwall screening, leading to the reduction of exciton binding energies and band gaps. When two tubes are both semiconducting, a clear exciton peak still survives even under depolarization effects for the outer tube, but the exciton peak of the inner tube has an asymmetric Fano line shape due to the coupling with continuum states of the outer tube. When a double-wall nanotube contains a metallic tube, either inner or outer, the exciton of the semiconducting tube loses its peak structure under depolarization effects.

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“…(See also the paper by Thess, et al 31 .) The observed plasmons are in the energy range of 5-7 eV and wave number ∼ 0.15Å −1 and are believed to be excitations of the π-electrons which are formed by the 2p z orbitals 19 . For metallic and narrow-gap semiconducting SWNTs, the plasmon excitation energies are of low frequency with energies in the range < 1 eV 19 .…”

Section: Introductionmentioning

confidence: 98%

“…The observed plasmons are in the energy range of 5-7 eV and wave number ∼ 0.15Å −1 and are believed to be excitations of the π-electrons which are formed by the 2p z orbitals 19 . For metallic and narrow-gap semiconducting SWNTs, the plasmon excitation energies are of low frequency with energies in the range < 1 eV 19 . These collective excitations are due principally by exciting the charge carriers in the low-energy bands near the Fermi level.…”

Section: Introductionmentioning

confidence: 98%

“…[1][2][3][4][5][6] Their extraordinary strength, unique electrical properties and their ability to conduct heat efficiently have generated considerable interest among both experimentalists and theoreticians. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Nanotubes may also be produced by synthesis methods, for instance multi-wall nanotubes (MWNTs) which consist of multiple layers of graphene rolled in on themselves to form a cylindrical tube. There are two models which can be used to describe the structures of multi-wall nanotubes.…”

Section: Introductionmentioning

confidence: 99%

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Model of plasmon excitations in a bundle and a two-dimensional array of nanotubes

2008

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We calculate the plasma excitations in a bundle as well as a two-dimensional (2D) periodic array of aligned parallel multishell nanotubes on a substrate. The carbon nanotubes are oriented perpendicular to the substrate. The model we use for the system is an electron gas confined to the surface of an infinitely long cylinder embedded in a background dielectric medium. Electron tunneling between individual tubules is neglected. We include the Coulomb interaction between electrons on the same tubule and on different tubules for the same nanotube and neighboring nanotubes. We present a self-consistent field theory for the dispersion equation for intrasubband and intersubband plasmon excitations. For both the bundle and 2D array of aligned parallel nanotubes, the dispersion relation of the collective modes is determined by a three-dimensional wave vector with components in the direction of the nanotube axes and in the transverse directions. The dispersion equation is solved numerically for a singlewall nanotube 2D array as well as a bundle, and the plasmon excitation energies are obtained as a function of wave vector. The intertube Coulomb interaction couples plasmons with different angular momenta m in individual nanotubes, lifting the ±m degeneracy of the single-nanotube modes. This effect is analyzed numerically as a function of the separation between the tubules. We show that the translational symmetry of the lattice is maintained in the plasmon spectrum for the periodic array, and the plasmon energies have a periodic dependence on the transverse wave vector q ⊥ . For the bundle, the Coulomb interaction between nanotubes gives rise to optical plasmon excitations.

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Low-frequency excitation spectra in double-walled armchair carbon nanotubes

Cited by 12 publications

References 39 publications

Interwall screening and excitons in double-wall carbon nanotubes

Interwall screening and excitons in double-wall carbon nanotubes

Cross-polarized excitons in double-wall carbon nanotubes

Model of plasmon excitations in a bundle and a two-dimensional array of nanotubes

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