Multiple memory formation in glassy landscapes

TL;DR

This paper investigates how interactions between particle clusters in sheared jammed packings enable the formation of multiple, long-lasting memories of shear amplitude, surpassing simple models and revealing complex memory encoding.

Contribution

It introduces an interacting cluster model that explains long training times, multi-period orbits, and simultaneous multiple memory formation in sheared jammed packings.

Findings

Interactions enable long training times and multi-period orbits.

Multiple memories can be encoded simultaneously due to interactions.

These memories differ from transient memories in sheared suspensions.

Abstract

Cyclically sheared jammed packings form memories of the shear amplitude at which they were trained by falling into periodic orbits where each particle returns to the identical position in subsequent cycles. While simple models that treat clusters of rearranging particles as isolated two-state systems offer insight into this memory formation, they fail to account for the long training times and multi-period orbits observed in simulated sheared packings. We show that adding interactions between rearranging clusters overcomes these deficiencies. In addition, interactions allow simultaneous encoding of multiple memories which would not have been possible otherwise. These memories are different in an essential way from those found in other systems, such as multiple transient memories observed in sheared suspensions, and contain information about the strength of the interactions.