Fluctuations, response and aging dynamics in a simple glass-forming liquid out of equilibrium

TL;DR

This study uses molecular dynamics simulations to analyze the aging and out-of-equilibrium relaxation dynamics of a simple glass-forming liquid after a quench, revealing complex time-dependent correlations and violations of fluctuation-dissipation relations.

Contribution

It provides new insights into the aging dynamics and response functions of a binary Lennard-Jones glass former out of equilibrium, including the characterization of correlation functions and response relations.

Findings

Correlation functions approach Edwards-Anderson value via power-law.

The function h(t) shows a slightly super-logarithmic growth.

Fluctuation-dissipation relation is violated similar to spin glasses.

Abstract

By means of molecular dynamics computer simulations we investigate the out of equilibrium relaxation dynamics of a simple glass former, a binary Lennard-Jones system, after a quench to low temperatures. We study both one time quantities and two-times correlation functions. Two-times correlation functions show a strong time and waiting time $t_w$ dependence. For large $t_w$ and times corresponding to the early $\beta$-relaxation regime the correlators approach the Edwards-Anderson value by means of a power-law in time. at long times $\tau$ the correlation functions can be expressed as $C_{\rm AG}(h(t_w+\tau)/h(t_w))$ and compute the function $h(t)$. This function is found to show a $t$-dependence which is a bit stronger than a logarithm and to depend on the observable considered. Finally we discuss our measurements of the time dependent response function. We find that at long times the correlation functions and the response are not related by the usual fluctuation dissipation theorem but that this relation is similar to the one found for spin glasses with one step replica symmetry breaking.