Phonon localization in glasses

Graebner, J. E.; Golding, B.; Allen, L. C.

doi:10.1103/physrevb.34.5696

Cited by 267 publications

(167 citation statements)

References 32 publications

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“…This effect which grows with the fourth power of the frequency was described long ago by Lord Rayleigh [8]. Although this mechanism has been invoked to explain the plateau in the thermal conductivity of glasses, or the "end" of acoustic branches [10,21,22,23], it has been known for quite some time that it is difficult to construct a model for glasses that produces strong Rayleigh scattering [24]. It has been recently reemphasized that the Rayleigh scattering of sound is generally too weak for it to play any appreciable role at frequencies below at least 1 THz [25,26].…”

Section: Introductionmentioning

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: Introductionmentioning

confidence: 99%

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

et al. 2005

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“…This region spans roughly 1.5 decades in temperature between several mK (lowest T accessed so far for the heat conductivity measurements) and to 1-10 K, depending on the substance. The short linear region at higher temperatures (20-60 K) corresponds to l mfp /λ ≃ 1, which actually implies complete phonon localization (Graebner et al, 1986) according to the heuristic Ioffe-Riegel criterion. This implies, among other things, that one can no longer use kinetic theory expressions for heat transfer at these temperatures, as a diffusive mechanism must prevail 1 .…”

Section: Introductionmentioning

confidence: 99%

The Microscopic Quantum Theory of Low Temperature Amorphous Solids

Lubchenko¹,

Wolynes²

2007

Advances in Chemical Physics

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The quantum excitations in glasses have long presented a set of puzzles for condensed matter physicists. A common view is that they are largely disordered analogs of elementary excitations in crystals, supplemented by two level systems which are chemically local entities coming from disorder. A radical revision of this picture argues that the excitations in low temperature glasses are deeply connected to the energy landscape of the glass when it vitrifies: the excitations are not low excited states built on a single ground state but locally defined resonances, high in the energy spectrum of a solid. According to a semiclassical analysis, the two level systems involve resonant collective tunneling motions of around two hundred molecular units which are relics of the mosaic of cooperative motions at the glass transition temperature Tg. The density of states of the TLS is determined by Tg and the mosaic's length scale, which is a weak function of the cooling rate. The universality of phonon scattering in insulating glasses is explained. The Boson Peak and the plateau in thermal conductivity, observed at higher temperatures, are also quantitatively understood within the picture as arising from the same cooperative motions, but now accompanied by thermal activation of the mosaic's vibrational modes. The dynamics of some of the local structural transitions have significant quantum corrections to the semiclassical picture. These corrections lead to a deviation of the heat capacity and conductivity from the standard tunneling model results and explain the anomalous time dependence of the heat capacity. Interaction between tunneling centers contributes to the large and negative value of the Grüneisen parameter often observed in glasses.

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“…Experimental measurements, estimates based on experiments, and modeling predictions have demonstrated that propagating modes contribute significantly to the thermal conductivity of amorphous silicon (a-Si) [4][5][6][7][8][9][10] and amorphous silicon nitride [11], but not to that of amorphous silica (a-SiO 2 ) [5,10,[12][13][14][15][16][17][18]. Notably, using broadband frequency domain thermoreflectance, Regner et al measured how the thermal conductivity of a-SiO 2 and a-Si thin films at a temperature of 300 K change with the thermal penetration depth associated with the heating laser, which identifies the depth normal to the surface at which the temperature amplitude is 1/e of its surface amplitude [10].…”

Section: Introductionmentioning

confidence: 99%

“…* mcgaughey@cmu.edu Traditionally, empirical expressions and simple models have been the only means to estimate MFPs in amorphous materials [12][13][14]22], while the Allen-Feldman (AF) theory can be used to model the nonpropagating modes [1,4].…”

Section: Introductionmentioning

confidence: 99%

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Thermal conductivity accumulation in amorphous silica and amorphous silicon

2014

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We predict the properties of the propagating and nonpropagating vibrational modes in amorphous silica (a-SiO 2 ) and amorphous silicon (a-Si) and, from them, thermal conductivity accumulation functions. The calculations are performed using molecular dynamics simulations, lattice dynamics calculations, and theoretical models. For a-SiO 2 , the propagating modes contribute negligibly to thermal conductivity (6%), in agreement with the thermal conductivity accumulation measured by Regner et al. [Nat. Commun. 4, 1640]. For a-Si, propagating modes with mean-free paths up to 1 μm contribute 40% of the total thermal conductivity. The predicted contribution to thermal conductivity from nonpropagating modes and the total thermal conductivity for a-Si are in agreement with the measurements of Regner et al. The accumulation in the measurements, however, takes place over a narrower band of mean-free paths (100 nm-1 μm) than that predicted (10 nm-1 μm).

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Phonon localization in glasses

Cited by 267 publications

References 32 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

The Microscopic Quantum Theory of Low Temperature Amorphous Solids

Thermal conductivity accumulation in amorphous silica and amorphous silicon

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