Connecting diffusion and dynamical heterogeneities in actively deformed amorphous systems

TL;DR

This study investigates how dynamical heterogeneities influence diffusion in actively deformed amorphous solids, revealing a direct link between diffusion coefficients and cooperative region sizes at low strain rates.

Contribution

It establishes a quantitative connection between self-diffusion and cooperative regions in amorphous solids under deformation, using scaling arguments and numerical simulations.

Findings

Diffusion coefficient correlates with cooperative region size.

Both diffusion and cooperative regions depend on strain rate and system size.

Passive tracer displacement reveals microscopic rheology.

Abstract

We present an extensive numerical study of dynamical heterogeneities and their influence on diffusion in an athermal mesoscopic model for actively deformed amorphous solids. At low strain rates the stress dynamics are governed by cooperative regions of plastic events. On the basis of scaling arguments as well as an extensive numerical study of an athermal elasto-plastic model, we show that there is a direct link between the self-diffusion coefficient and the size of cooperative regions at low strain rates. Both depend strongly on rate and on system size. A measure of the mean square displacement of passive tracers in deformed amorphous media thus gives information about the microscopic rheology, such as the geometry of the cooperative regions and their scaling with strain rate and system size.