Anomalous Stress Fluctuations in Athermal Two Dimensional Amorphous Solids

TL;DR

This study reveals that in two-dimensional amorphous solids, stress fluctuations increase at large scales, challenging existing theories and suggesting such behavior might be a universal feature of these materials.

Contribution

The paper provides numerical evidence of algebraically increasing stress fluctuations at large scales in 2D amorphous solids, contrasting recent theoretical predictions.

Findings

Stress fluctuations grow algebraically at small wavenumbers.

The length scale of fluctuations does not significantly change near jamming.

Similar large-scale stress fluctuations are observed in Lennard-Jones liquids.

Abstract

We numerically study the local stress distribution within athermal, isotropically stressed, mechanically stable, packings of bidisperse frictionless disks above the jamming transition in two dimensions. Considering the Fourier transform of the local stress, we find evidence for algebraically increasing fluctuations in both isotropic and anisotropic components of the stress tensor at small wavenumbers, contrary to recent theoretical predictions. Such increasing fluctuations imply a lack of self-averaging of the stress on large length scales. The crossover to these increasing fluctuations defines a length scale $\ell_0$, however it appears that $\ell_0$ does not vary much with packing fraction $\phi$, nor does $\ell_0$ seem to be diverging as $\phi$ approaches the jamming $\phi_J$. We also find similar large length scale fluctuations of stress in the inherent states of a quenched Lennard-Jones liquid, leading us to speculate that such fluctuations may be a general property of amorphous solids in two dimensions.