Hyper-Raman Scattering Observation of the Boson Peak in Vitreous Silica

Hehlen, Bernard; Courtens, E.; Vacher, R.; Yamanaka, Akio; Kataoka, M.; Inoue, Kuon

doi:10.1103/physrevlett.84.5355

Cited by 148 publications

(105 citation statements)

References 27 publications

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“…To achieve Ωτ th = 1 would require Ω/2π ≃ 3 THz which is already above ω c /2π ≃ 2 THz. One runs then into a regime in which the sound waves are presumably hybridizing [26] with the SiO 4 librational mode [60], producing the boson peak [30]. Although such a measurement might give an indication about v ∞ , it is certainly not a clean cut situation.…”

Section: Discussionmentioning

confidence: 99%

Anharmonic versus relaxational sound damping in glasses. I. Brillouin scattering from densified silica

et al. 2005

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This series discusses the origin of sound damping and dispersion in glasses. In particular, we address the relative importance of anharmonicity versus thermally activated relaxation. In this first article, Brillouin-scattering measurements of permanently densified silica glass are presented. It is found that in this case the results are compatible with a model in which damping and dispersion are only produced by the anharmonic coupling of the sound waves with thermally excited modes. The thermal relaxation time and the unrelaxed velocity are estimated.

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Section: Discussionmentioning

confidence: 99%

Anharmonic versus relaxational sound damping in glasses. I. Brillouin scattering from densified silica

et al. 2005

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“…Another possible reason is more profound. In silica the BP relates to rigid tetrahedra rotations [33] which cannot be pointlike in this connected network [34]. Thus, it produces a diffuse optic branch which hybridizes with the acoustic branch, an effect that depends both on the frequency and size of the excitations.…”

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confidence: 99%

Observation of the Onset of Strong Scattering on High Frequency Acoustic Phonons in Densified Silica Glass

et al. 2003

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The linewidth of longitudinal acoustic waves in densified silica glass is obtained by inelastic x-ray scattering. It increases with a high power α of the frequency up to a crossover where the waves experience strong scattering. We find that α is at least 4, and probably larger. Resonance and hybridization of acoustic waves with the boson-peak modes seems to be a more likely explanation for these findings than Rayleigh scattering from disorder. PACS numbers: 63.50+x, 78.35+c, 78.70.Ck A controversy regarding the fate of very high frequency acoustic-like excitations in glasses arose in recent years [1,2]. Acoustic waves propagate in glasses up to rather high frequencies, for example up to at least Ω/2π ≃ 0.4 THz in vitreous silica, v-SiO 2 [3,4]. However, silica shows a pronounced "plateau" in the temperature (T ) dependence of its thermal conductivity κ(T ) [5]. This feature was explained by postulating the existence of a rapid crossover of acoustic waves into a regime where they experience strong scattering [6]. In v-SiO 2 , this crossover is expected at a frequency Ω co /2π ≃ 1 THz [7]. For the observed horizontal plateau to occur, besides strong scattering of thermal phonons, phonons of lower Ω must also experience a sufficiently strong T -independent scattering [8]. Several models predict that the inhomogeneous width of acoustic waves can increase with a high power of Ω, typically in Ω 4 [9, 10], leading to this rapid crossover. However, the origin of the high power remained debated, whether Rayleigh scattering from structural defects [6], or resonance with local modes [10,11,12]. Rayleigh scattering seems generally too weak in materials as homogeneous as dense glasses to be able to account for the relatively low Ω co suggested by the position of the plateau [6,8]. The local modes are seen in the "boson peak" (BP) and produce an excess over the Debye specific heat [13]. Successful models based on resonance or on soft potentials were developed to describe the observed properties, e.g. in [10,14,15].It might seem, judging from some recent literature [2], that the above picture should be revised after it became possible to observe in glasses the spectrum of longitudinal acoustic (LA) waves at THz frequencies with x-ray Brillouin scattering (BS) [16]. This new experimental tool is important here, as it potentially allows to check some of the previous conjectures. It led to many publications claiming to prove that sound propagates at frequencies much above the early expectations for Ω co , e.g. [17,18]. In this respect, it must be emphasized that inelastic x-ray scattering (IXS) still is a difficult spectroscopy with severe limitations on resolution and intensity. Firstly, it is practically not possible with current instruments to investigate scattering vectors Q below ∼ 1 nm −1 , a value which happens to coincide with the expected wave vector q at crossover, q co , in v-SiO 2 [7] and in many other glasses. Secondly, the narrowest instrumental profile allowing for sufficient intensity [19] still has an energy w...

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“…The BP is an anomalous override of the low-frequency phonon density over the Debye density. The BP was observed in the Raman and Brillouin scattering spectra (Hehlen et al, 2000;Rufflé et al, 2006) and in inelastic neutron scattering experiments (Buchenau et al, 1984) as maxima in the frequency dependence  2   or  2 I  (   I  is the scattering intensity). These peaks appear in the low-frequency region (between 0.5 and 2 THz) of the vibration density of states (Ahmad et al, 1986), i.e.…”

Section: Low-frequency Characteristics Of the Phonon Spectra Of Disormentioning

confidence: 99%

The Features of Low Frequency Atomic Vibrations and Propagation of Acoustic Waves in Heterogeneous Systems

Feher¹,

Syrkin²,

Feodosyev³

et al. 2011

Waves in Fluids and Solids

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Hyper-Raman Scattering Observation of the Boson Peak in Vitreous Silica

Cited by 148 publications

References 27 publications

Anharmonic versus relaxational sound damping in glasses. I. Brillouin scattering from densified silica

Anharmonic versus relaxational sound damping in glasses. I. Brillouin scattering from densified silica

Observation of the Onset of Strong Scattering on High Frequency Acoustic Phonons in Densified Silica Glass

The Features of Low Frequency Atomic Vibrations and Propagation of Acoustic Waves in Heterogeneous Systems

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