Intermittency in aging

TL;DR

This paper investigates the violation of the fluctuation-dissipation relation during aging in gels and glasses, revealing intermittent dynamics with large fluctuations that persist over hours and vary with frequency.

Contribution

It provides experimental evidence of fluctuation-dissipation relation violations during aging in gels and glasses, highlighting the role of intermittent dynamics.

Findings

FDR is strongly violated during aging in gel and polymer glass.

Violation amplitude and duration decrease with frequency.

Intermittent large fluctuations characterize the aging dynamics.

Abstract

The fluctuation-dissipation relation (FDR) is measured on the dielectric properties of a gel (Laponite) and of a polymer glass (polycarbonate). For the gel it is found that during the transition from a fluid-like to a solid-like state the fluctuation dissipation theorem is strongly violated. The amplitude and the persistence time of this violation are decreasing functions of frequency. Around $1Hz$ it may persist for several hours. A very similar behavior is observed in polycarbonate after a quench below the glass transition temperature. In both cases the origin of this violation is a highly intermittent dynamics characterized by large fluctuations. The relevance of these results for recent models of aging are discussed.