Excitons in Boron Nitride Nanotubes: Dimensionality Effects

Wirtz, Ludger; Marini, Andrea; Rubio, Ángel

doi:10.1103/physrevlett.96.126104

Cited by 369 publications

(385 citation statements)

References 28 publications

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“…On the experimental side, the challenge is the fabrication of high quality single crystals which has been achieved only recently 2 . On the theoretical side, it is well established that the band-structure of hBN displays an indirect gap 3,4 and the optical absorption spectrum is dominated by correlation effects leading to a strong Frenkel-type excitonic peak at 5.8 eV [4][5][6] in agreement with the experimental findings 1 . However, the origin of the fine structure of the absorption and luminescence spectra around this peak is still under debate [7][8][9] .…”

supporting

confidence: 84%

Anisotropic excitonic effects in the energy loss function of hexagonal boron nitride

et al. 2011

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We demonstrate that the valence energy-loss function of hexagonal boron nitride (hBN) displays a strong anisotropy in shape, excitation energy and dispersion for momentum transfer q parallel or perpendicular to the hBN layers. This is manifested by e.g. an energy shift of 0.7 eV that cannot be captured by single-particle approaches and is a demonstration of a strong anisotropy in the two-body electron-hole interaction. Furthermore, for in-plane directions of q we observe a splitting of the π-plasmon in the ΓM direction that is absent in the ΓK direction and this can be traced back to band-structure effects.

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supporting

confidence: 84%

Anisotropic excitonic effects in the energy loss function of hexagonal boron nitride

et al. 2011

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“…The LDA-ALDA spectrum shows a broad absorption peak with an onset at 4.5 eV in good agreement with literature. 56 The GLLBSC-ALDA spectrum is essentially identical to the LDA-ALDA, but blue shifted by the difference in the band gap. For the BSE calculation, the Brillouin zone was sampled on a non--centered 32 × 32 Monkhorst-Pack grid, and 70 unoccupied bands were included to obtain the screened interaction W .…”

Section: Graphene/boron-nitridementioning

confidence: 91%

“…The optical properties of layered BN sheets as well as BN nanotubes have been studied extensively both experimentally 55 and theoretically. 13,56 Upon adsorption of graphene onto a h-BN sheet, a small band gap of around 10-200 meV, depending on the configuration and interplane distance, emerges. 57 The ground state electronic properties, including the role of dispersive forces, and the band structure have been studied.…”

Section: Graphene/boron-nitridementioning

confidence: 99%

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Optical properties of bulk semiconductors and graphene/boron nitride: The Bethe-Salpeter equation with derivative discontinuity-corrected density functional energies

2012

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We present an efficient implementation of the Bethe-Salpeter equation (BSE) for optical properties of materials in the projector augmented wave method GPAW. Single-particle energies and wave functions are obtained from the GLLBSC functional which explicitly includes the derivative discontinuity, is computationally inexpensive, and yields excellent fundamental gaps. Electron-hole interactions are included through the BSE using the statically screened interaction evaluated in the random phase approximation. For a representative set of semiconductors and insulators we find excellent agreement with experiments for the dielectric functions, onset of absorption, and lowest excitonic features. For the two-dimensional systems of graphene and hexagonal boron-nitride (h-BN) we find good agreement with previous many-body calculations. For the graphene/h-BN interface, we find that the fundamental and optical gaps of the h-BN layer are reduced by 2.0 eV and 0.7 eV, respectively, compared to freestanding h-BN. This reduction is due to image charge screening which shows up in the GLLBSC calculation as a reduction (vanishing) of the derivative discontinuity.

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“…Since h-BN is a relevant material for UV lasing, it is imperative to resolve the existing controversies and critically assess the quality of the ab initio calculations. Furthermore, we need exact information on the lattice dynamics in order to properly understand the contributions due to electron-phonon coupling observed in the cathodoluminescence and absorption spectra of h-BN [7] and BN nanotubes [15,16].In this Letter we address the above discrepancies in the vibrational properties by reporting inelastic x-ray scattering (IXS) measurements and first principles calculations of the phonon dispersion relations of bulk h-BN. We also report ab initio calculations of the phonon dispersion of a monolayer of h-BN on a nickel substrate.…”

mentioning

confidence: 99%

Vibrational Properties of Hexagonal Boron Nitride: Inelastic X-Ray Scattering andAb InitioCalculations

et al. 2007

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The phonon dispersion relations of bulk hexagonal boron nitride have been determined from inelastic x-ray scattering measurements and analyzed by ab initio calculations. Experimental data and calculations show an outstanding agreement and reconcile the controversies raised by recent experimental data obtained by electron-energy loss spectroscopy and second-order Raman scattering. DOI: 10.1103/PhysRevLett.98.095503 PACS numbers: 63.20.Dj, 61.10.Eq, 63.10.+a, 71.15.Mb Besides their intermediate structure between twodimensional sheets and 3D crystals, layered compounds are relevant materials for storage of other compounds [1] and as potential building blocks for nanotubes [2]. Among these materials, graphite and hexagonal boron nitride (h-BN) have drawn most of the attention due to their simple hexagonal structure, their fascinating properties, and the successful realization of carbon-[3] and more recently BN [4 -6] nanotubes. A wide band gap semiconductor, h-BN, has been grown successfully very recently as a single crystal. It exhibits a lasing behavior at 5.8 eV that makes it attractive for optoelectronic applications in the ultraviolet energy range [7].Despite the tremendous effort devoted to the characterization of physical properties of h-BN, the lattice dynamics, responsible for the elastic and thermodynamic properties such as the heat capacity and the thermal expansion, are still under debate. First principles calculations are generally accepted as the most accurate theoretical description of the lattice dynamics [8]. Recently, for h-BN, the validity of state of the art ab initio calculations was put in doubt by two experiments: Rokuta et al. [9] reported the only experimental data available for the phonon dispersion relations by electron-energy loss spectroscopy (EELS) performed on a monolayer of h-BN deposited on a Ni(111) substrate. Among several deviations from ab initio calculations of the lattice dynamics both for a monolayer [10,11] and for bulk h-BN [12,13], the EELS data show a degeneracy at the K point between acoustic (ZA) and optical (ZO) modes polarized along the c axis. The origin of this degeneracy has not been clarified yet. More recently [14], second-order Raman spectra of single crystalline h-BN revealed two features that contested the predictions based on a simple doubling of the energy scale of ab initio calculations for the one-phonon density of states, suggesting deviations up to 40% for the calculated energy of the TA branch in the K-M region. Since h-BN is a relevant material for UV lasing, it is imperative to resolve the existing controversies and critically assess the quality of the ab initio calculations. Furthermore, we need exact information on the lattice dynamics in order to properly understand the contributions due to electron-phonon coupling observed in the cathodoluminescence and absorption spectra of h-BN [7] and BN nanotubes [15,16].In this Letter we address the above discrepancies in the vibrational properties by reporting inelastic x-ray scattering (IXS) measurements...

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Excitons in Boron Nitride Nanotubes: Dimensionality Effects

Cited by 369 publications

References 28 publications

Anisotropic excitonic effects in the energy loss function of hexagonal boron nitride

Anisotropic excitonic effects in the energy loss function of hexagonal boron nitride

Optical properties of bulk semiconductors and graphene/boron nitride: The Bethe-Salpeter equation with derivative discontinuity-corrected density functional energies

Vibrational Properties of Hexagonal Boron Nitride: Inelastic X-Ray Scattering andAb InitioCalculations

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