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Boson Peak

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D Fioretto – 1st expert on this subject based on the ideXlab platform

  • stress induced modification of the Boson Peak scaling behavior
    Journal of Physical Chemistry B, 2013
    Co-Authors: S Corezzi, S Caponi, F Rossi, D Fioretto

    Abstract:

    The scaling behavior of the so-called Boson Peak in glass-formers and its relation to the elastic properties of the system remains a source of controversy. Here the Boson Peak in a binary reactive mixture is measured by Raman scattering (i) on cooling the unreacted mixture well below its glass-transition temperature and (ii) after quenching to very low temperature the mixture at different times during isothermal polymerization. We find that the scaling behavior of the Boson Peak with the properties of the elastic medium — as measured by the Debye frequency — holds for states in which the elastic moduli follow a generalized Cauchy-like relationship, and breaks down in coincidence with the departure from this relation. A possible explanation is given in terms of the development of long-range stresses in glasses. The present study provides new insight into the Boson Peak behavior and is able to reconcile the apparently conflicting results presented in literature.

  • stress induced modification of the Boson Peak scaling behavior
    arXiv: Soft Condensed Matter, 2013
    Co-Authors: S Corezzi, S Caponi, F Rossi, D Fioretto

    Abstract:

    The scaling behavior of the so-called Boson Peak in glass-formers and its relation to the elastic properties of the system remains a source of controversy. Here, the Boson Peak in a binary reactive mixture is measured by Raman scattering (i) on cooling the unreacted mixture well below its glass transition temperature and (ii) after quenching to very low temperature the mixture at different times during isothermal polymerization. These different paths to the glassy phase are able to generate glasses with different amounts of residual stresses, as evidenced by the departure of the elastic moduli from a Cauchy-like relationship. We find that the scaling behavior of the Boson Peak with the properties of the elastic medium — as measured by the Debye frequency — holds for states in which the system is able to release internal stress and breaks down in the presence of residual stresses. These findings provide new insight into the Boson Peak behavior and are able to reconcile the apparently conflicting results presented in literature.

  • equivalence of the Boson Peak in glasses to the transverse acoustic van hove singularity in crystals
    Physical Review Letters, 2011
    Co-Authors: A I Chumakov, R Ruffer, G Monaco, A Monaco, Wilson A Crichton, Alexey Bosak, A Meyer, F Kargl, L Comez, D Fioretto

    Abstract:

    We compare the atomic dynamics of the glass to that of the relevant crystal. In the spectra of inelastic scattering, the Boson Peak of the glass appears higher than the transverse acoustic (TA) singularity of the crystal. However, the density of states shows that they have the same number of states. Increasing pressure causes the transformation of the Boson Peak of the glass towards the TA singularity of the crystal. Once corrected for the difference in the elastic medium, the Boson Peak matches the TA singularity in energy and height. This suggests the identical nature of the two features.

Alain Pasturel – 2nd expert on this subject based on the ideXlab platform

  • structural and dynamic origin of the Boson Peak in a cu zr metallic glass
    Physical Review B, 2012
    Co-Authors: Noel Jakse, Abdallah Nassour, Alain Pasturel

    Abstract:

    Using molecular dynamics simulations, we studied the short-time dynamics of the amorphous Cu50Zr50 alloy. We determined the occurrence of a well-defined Boson Peak in agreement with experimental observations. Our results indicate that the structural origin of the Boson Peak can be related to Cu and Zr atoms having large mean-square amplitudes in low-density defective local structures. Moreover, we show that these structural motifs display quasilocalized modes that resonantly couple with transverse phonons, leading to the accumulation of the low-energy modes around the Boson Peak. Finally, the correlation between the attenuation of sound and the Boson Peak is discussed.

  • Structural and dynamic origin of the Boson Peak in a Cu-Zr metallic glass
    Physical Review B, 2012
    Co-Authors: Noel Jakse, Abdallah Nassour, Alain Pasturel

    Abstract:

    Using molecular dynamics simulations, we studied the short-time dynamics of the amorphous Cu 50Zr 50 alloy. We determined the occurrence of a well-defined Boson Peak in agreement with experimental observations. Our results indicate that the structural origin of the Boson Peak can be related to Cu and Zr atoms having large mean-square amplitudes in low-density defective local structures. Moreover, we show that these structural motifs display quasilocalized modes that resonantly couple with transverse phonons, leading to the accumulation of the low-energy modes around the Boson Peak. Finally, the correlation between the attenuation of sound and the Boson Peak is discussed. © 2012 American Physical Society.

D. A. Parshin – 3rd expert on this subject based on the ideXlab platform

  • Application of the random matrix theory to the Boson Peak in glasses.
    arXiv: Disordered Systems and Neural Networks, 2019
    Co-Authors: D. A. Conyuh, Y. M. Beltukov, D. A. Parshin

    Abstract:

    The density of vibrational states $g(\omega)$ of an amorphous system is studied by using the random-matrix theory. Taking into account the most important correlations between elements of the random matrix of the system, equations for the density of vibrational states $g(\omega)$ are obtained. The analysis of these equations shows that in the low-frequency region the vibrational density of states has the Debye behavior $g(\omega) \sim \omega^2$. In the higher frequency region, there is the Boson Peak as an additional contribution to the density of states. The obtained equations are in a good agreement with the numerical results and allow us to find an exact shape of the Boson Peak.

  • Boson Peak in various random-matrix models
    JETP Letters, 2016
    Co-Authors: Y. M. Beltukov, D. A. Parshin

    Abstract:

    A so-called Boson Peak in the reduced density g (ω)ω^2 of vibrational states is one of the most universal properties of amorphous solids (glasses). It quantifies the excess density of states above the Debye value at low frequencies ω. Its nature is not fully understood and, at a first sight, is nonuniversal. It is shown in this work that, under rather general assumptions, the Boson Peak emerges in a natural way in very dissimilar models of stable random dynamic matrices possessing translational symmetry. This Peak can be shifted toward both higher and lower frequencies (down to zero frequency) by varying the parameters of the distribution and the degree of disorder in the system. The frequency ω_b of the Boson Peak appears to be proportional to the elastic modulus E of the system in all cases under investigation.

  • vibrational instability two level systems and the Boson Peak in glasses
    Physical Review B, 2007
    Co-Authors: D. A. Parshin, H R Schober, V L Gurevich

    Abstract:

    We show that the same physical mechanism is fundamental for two seemingly different phenomena such as the formation of two-level systems in glasses and the Boson Peak in the reduced density of low-frequency vibrational states $g(\ensuremath{\omega})∕{\ensuremath{\omega}}^{2}$. This mechanism is the vibrational instability of weakly interacting harmonic modes. Below some frequency ${\ensuremath{\omega}}_{c}⪡{\ensuremath{\omega}}_{0}$ (where ${\ensuremath{\omega}}_{0}$ is of the order of Debye frequency), the instability, controlled by the anharmonicity, creates a new stable universal spectrum of harmonic vibrations with a Boson Peak feature as well as double-well potentials with a wide distribution of barrier heights. Both are determined by the strength of the interaction $I\ensuremath{\propto}{\ensuremath{\omega}}_{c}$ between the oscillators. Our theory predicts in a natural way a small value for the important dimensionless parameter $C=\overline{P}{\ensuremath{\gamma}}^{2}∕\ensuremath{\rho}{v}^{2}\ensuremath{\approx}{10}^{\ensuremath{-}4}$ for two-level systems in glasses. We show that $C\ensuremath{\approx}{(W∕\ensuremath{\hbar}{\ensuremath{\omega}}_{c})}^{3}\ensuremath{\propto}{I}^{\ensuremath{-}3}$ and decreases with increasing interaction strength $I$. The energy $W$ is an important characteristic energy in glasses and is of the order of a few Kelvin. This formula relates the two-level system’s parameter $C$ with the width of the vibration instability region ${\ensuremath{\omega}}_{c}$, which is typically larger or of the order of the Boson Peak frequency ${\ensuremath{\omega}}_{b}$. Since $\ensuremath{\hbar}{\ensuremath{\omega}}_{c}\ensuremath{\gtrsim}\ensuremath{\hbar}{\ensuremath{\omega}}_{b}⪢W$, the typical value of $C$ and, therefore, the number of active two-level systems is very small, less than 1 per $1\ifmmode\times\else\texttimes\fi{}{10}^{7}$ of oscillators, in good agreement with experiment. Within the unified approach developed in the present paper, the density of the tunneling states and the density of vibrational states at the Boson Peak frequency are interrelated.