Electrical noise properties in aging materials

TL;DR

This study investigates electric thermal noise in aging materials, revealing strong intermittency and FDT violations during their transition from fluid-like to solid-like states, with results aligning with models of aging dynamics.

Contribution

It provides experimental evidence of intermittency and FDT violation in aging materials, linking noise properties to aging models and their dependence on quench speed and concentration.

Findings

Electric noise shows strong intermittency during aging.

FDT violations can persist for hours at low frequency.

Noise statistics depend on quench speed and sample concentration.

Abstract

The electric thermal noise has been measured in two aging materials, a colloidal suspension (Laponite) and a polymer (polycarbonate), presenting very slow relaxation towards equilibrium. The measurements have been performed during the transition from a fluid-like to a solid-like state for the gel and after a quench for the polymer. For both materials we have observed that the electric noise is characterized by a strong intermittency, which induces a large violation of the Fluctuation Dissipation Theorem (FDT) during the aging time, and may persist for several hours at low frequency. The statistics of these intermittent signals and their dependance on the quench speed for the polymer or on sample concentration for the gel are studied. The results are in a qualitative agreement with recent models of aging, that predict an intermittent dynamics.