Propagating irreversibility fronts in cyclically-sheared suspensions

TL;DR

This paper investigates the emergence of diffuse, critical interfaces in cyclically-sheared suspensions, linking front width to diverging correlation lengths near phase transitions, with implications for understanding irreversibility in complex systems.

Contribution

It demonstrates that diffuse interfaces occur generally at critical points in incompressible phases, extending understanding of phase transition phenomena in suspensions.

Findings

Diffuse traveling fronts mark the boundary between reversible and irreversible phases.

Front width diverges as the system approaches a critical transition.

Avalanche dynamics reveal diverging correlation lengths near criticality.

Abstract

The interface separating a liquid from its vapor phase is diffuse: the composition varies continuously from one phase to the other over a finite length. Recent experiments on dynamic jamming fronts in two dimensions [Waitukaitis et al., Europhysics Letters 102, 44001 (2013)] identified a diffuse interface between jammed and unjammed discs. In both cases, the thickness of the interface diverges as a critical transition is approached. We investigate the generality of this behavior using a third system: a model of cyclically-sheared non-Brownian suspensions. As we sediment the particles towards a boundary, we observe a diffuse traveling front that marks the interface between irreversible and reversible phases. We argue that the front width is linked to a diverging correlation lengthscale in the bulk, which we probe by studying avalanches near criticality. Our results show how diffuse interfaces may arise generally when an incompressible phase is brought to a critical point.