Multiple transient memories in sheared suspensions: robustness, structure, and routes to plasticity

TL;DR

This paper investigates multiple transient memories in sheared suspensions, demonstrating their robustness, the influence of particle structure, and how overdriving can control memory formation and retention.

Contribution

It extends previous work by exploring the robustness, structural effects, and control mechanisms of transient memories in simulated sheared suspensions.

Findings

Transient memories are robust across different models.

Memory formation is independent of particle correlation details.

Overdriving can control memory retention.

Abstract

Multiple transient memories, originally discovered in charge-density-wave conductors, are a remarkable and initially counterintuitive example of how a system can store information about its driving. In this class of memories, a system can learn multiple driving inputs, nearly all of which are eventually forgotten despite their continual input. If sufficient noise is present, the system regains plasticity so that it can continue to learn new memories indefinitely. Recently, Keim & Nagel showed how multiple transient memories could be generalized to a generic driven disordered system with noise, giving as an example simulations of a simple model of a sheared non-Brownian suspension. Here, we further explore simulation models of suspensions under cyclic shear, focussing on three main themes: robustness, structure, and overdriving. We show that multiple transient memories are a robust feature independent of many details of the model. The steady-state spatial distribution of the particles is sensitive to the driving algorithm; nonetheless, the memory formation is independent of such a change in particle correlations. Finally, we demonstrate that overdriving provides another means for controlling memory formation and retention.