Amorphous solids or glasses are known to exhibit stretched-exponential decay over broad time intervals in several of their macroscopic observables: intermediate scattering function, dielectric relaxation modulus, time-dependent elastic modulus, etc. This behaviour is prominent especially near the glass transition. In this Letter we show, on the example of dielectric relaxation, that stretched-exponential relaxation is intimately related to the peculiar lattice dynamics of glasses. By reformulating the Lorentz model of dielectric matter in a more general form, we express the dielectric response as a function of the vibrational density of states (DOS) for a random assembly of spherical particles interacting harmonically with their nearest-neighbours. Surprisingly we find that near the glass transition for this system (which coincides with the Maxwell rigidity transition in this model), the dielectric relaxation is perfectly consistent with stretched-exponential behaviour with Kohlrausch exponents 0.56 < beta < 0.65, which is the range where exponents are measured in most experimental systems. Crucially, the root cause of stretched-exponential relaxation can be traced back to soft modes (boson-peak) in the DOS.
The relation between stretched-exponential relaxation and the vibrational density of states in glassy disordered systems / B. Cui, R. Milkus, A. Zaccone. - In: PHYSICS LETTERS A. - ISSN 0375-9601. - 381:5(2017 Feb 05), pp. 446-451.
|Titolo:||The relation between stretched-exponential relaxation and the vibrational density of states in glassy disordered systems|
ZACCONE, ALESSIO (Ultimo) (Corresponding)
|Parole Chiave:||glasses; Boson peak; dielectric relaxation; Stretched-exponential; Kohlrausch; Jamming|
|Settore Scientifico Disciplinare:||Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici|
Settore FIS/03 - Fisica della Materia
|Data di pubblicazione:||5-feb-2017|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1016/j.physleta.2016.12.003|
|Appare nelle tipologie:||01 - Articolo su periodico|