Direct evidence for a characteristic dynamic lengthscale in the intermediate phase of glasses

TL;DR

This study provides direct evidence of a characteristic dynamic lengthscale in the intermediate phase of glasses, revealing how ion diffusion paths change with composition and rigidity.

Contribution

It introduces a novel measurement of a dynamical lengthscale in glasses, demonstrating its maximum in the intermediate phase, a key insight into glass dynamics.

Findings

Maximum lengthscale observed in the intermediate phase

Dynamic lengthscale correlates with rigidity transition

First direct evidence of a dynamical lengthscale in this context

Abstract

AC conductivity spectra of xAgI-(1-x)AgPO$_3$ fast ion conducting glasses spanning the flexible, intermediate (isostatically rigid) and stressed rigid phases are analyzed. The rescaled frequency dependent spectra are mapped into time-dependent mean square displacements out of which a typical lengthscale characterizing the spatial extent $\sqrt{\langle R^2(\infty)\rangle}$ of non-random diffusion paths is computed. The latter quantity is studied as a function of AgI composition, it is found to display a maximum in the intermediate phase, providing the first clear evidence of a typical lengthscale of a dynamical nature when a system becomes isostatically rigid and enters the intermediate phase.