Glassiness, Rigidity and Jamming of Frictionless Soft Core Disks

TL;DR

This study investigates how different protocols like cooling, compression, and shear influence the jamming behavior of frictionless soft disks, revealing a unique shear-driven jamming point and clarifying its relation to glassy states and rigidity.

Contribution

It demonstrates that shear-driven jamming leads to a unique critical density independent of initial conditions, contrasting with other methods that depend on initial configurations.

Findings

Shear disrupts particle clustering, narrowing the jamming density range.

Cooling and compression produce a broad range of jamming densities.

Shear-driven jamming density is independent of initial configurations at low shear rates.

Abstract

The jamming of bi-disperse soft core disks is considered, using a variety of different protocols to produce the jammed state. In agreement with other works, we find that cooling and compression can lead to a broad range of jamming packing fractions $\phi_J$, depending on cooling rate and initial configuration; the larger the degree of big particle clustering in the initial configuration, the larger will be the value of $\phi_J$. In contrast, we find that shearing disrupts particle clustering, leading to a much narrower range of $\phi_J$ as the shear strain rate varies. In the limit of vanishingly small shear strain rate, we find a unique non-trivial value for the jamming density that is independent of the initial system configuration. We conclude that shear driven jamming is a unique and well defined critical point in the space of shear driven steady states. We clarify the relation between glassy behavior, rigidity and jamming in such systems and relate our results to recent experiments.