Dynamic susceptibilities in dense soft athermal spheres under a finite-rate shear

TL;DR

This study uses molecular dynamics simulations to analyze how dense soft athermal spheres respond mechanically to finite-rate shear, revealing susceptibility ridges analogous to Widom lines in phase transitions.

Contribution

It introduces a novel analysis of susceptibilities in sheared dense soft spheres, highlighting their dependence on volume fraction and shear rate, and draws parallels to critical phenomena.

Findings

Susceptibilities form ridges on the volume fraction-shear rate plane.

Susceptibility ridges resemble Widom lines near critical points.

Mechanical response fluctuations depend on shear rate and volume fraction.

Abstract

The mechanical responses of dense packings of soft athermal spheres under a finite-rate shear are studied by means of molecular dynamics simulations. We investigate the volume fraction and shear rate dependence of the fluctuations in the shear stress and the interparticle contact number. In particular, we quantify them by defining the susceptibility as the ratio of the global to local fluctuations. The obtained susceptibilities form ridges on the volume fraction-shear rate plane, which are reminiscent of the Widom lines around the critical point in an equilibrium phase transition.