Metastability at the Yield-Stress Transition in Soft Glasses

TL;DR

This study investigates the metastable solid-liquid transition in soft glasses under heterogeneous stress, revealing bimodal dynamics and long-range correlations near the yield point, with implications for experimental validation.

Contribution

It demonstrates the existence of metastable states and bimodal dynamics in soft glasses near yield stress, linking microscopic droplet behavior to macroscopic rheology.

Findings

Metastability involves two distinct stable rheological states.

Bimodal distribution of droplet displacements indicates intermittent transitions.

Similar behavior observed in pressure-driven flow, suggesting experimental relevance.

Abstract

We study the solid-to-liquid transition in a two-dimensional fully periodic soft-glassy model with an imposed spatially heterogeneous stress. The model we consider consists of droplets of a dispersed phase jammed together in a continuous phase. When the peak value of the stress gets close to the yield stress of the material, we find that the whole system intermittently tunnels to a metastable "fluidized" state, which relaxes back to a metastable "solid" state by means of an elastic-wave dissipation. This macroscopic scenario is studied through the microscopic displacement field of the droplets, whose time statistics displays a remarkable bimodality. Metastability is rooted in the existence, in a given stress range, of two distinct stable rheological branches as well as long-range correlations (e.g., large dynamic heterogeneity) developed in the system. Finally, we show that a similar behavior holds for a pressure-driven flow, thus suggesting possible experimental tests.