Aging of amorphous materials under cyclic strain

TL;DR

This paper investigates the aging behavior of amorphous materials under cyclic strain, revealing a universal logarithmic decay in dissipation and identifying the structural model that best captures this phenomenon.

Contribution

It demonstrates that only the random network of bi-stable elastic bonds model reproduces experimental aging behaviors under cyclic driving, highlighting the importance of complex energy landscapes.

Findings

Logarithmic decay of dissipation per cycle observed

Only the structural model with bi-stable elastic bonds matches experiments

Cyclic driving effectively probes energy landscape complexity

Abstract

Amorphous materials driven away from equilibrium display a diverse repertoire of complex, history-dependent behaviors. One striking feature is a failure to return to equilibrium after an abrupt change in otherwise static external conditions. Instead, amorphous materials often exhibit physical aging: an ever-slowing, nonexponential relaxation that can span a huge range of timescales. Here we examine the aging behavior of three different amorphous materials subjected to slow periodic driving. The results reveal a generic aging phenomenon characterized by a logarithmic decay of dissipation per cycle. This observation is evaluated against several mesoscopic models of amorphous matter that successfully capture aging under static conditions: (i) a collection of noninteracting relaxation processes (ii) a noisy hysteron model with random pairwise interactions, and (iii) a structural model consisting of a random network of bi-stable elastic bonds. We find that only the latter model reproduces all experimental findings and relate its success to its persistent, slow exploration of a complex energy landscape with clear signatures of replica symmetry breaking. Thus, cyclic driving emerges as a simple yet powerful protocol to characterize amorphous materials, probe their complex energy landscapes, and distinguish between different models.