Asymmetric driving reveals a glassy way to remember

Studies of glassy systems have demonstrated that cyclic driving forms memories of amplitude. We show that choice of driving protocol exposes dramatically different features of this memory. We model rearranging soft spots in sheared amorphous solids as hysterons. Cyclic shear with positive and negative shear strain reveals a return-point memory of multiple strains known from experiments and molecular dynamics simulations, while asymmetric driving (e.g. only positive shear strains) suppresses it. However, when we introduce frustrated interactions between hysterons, the capacity for multiple memories is restored. We show that this memory is due to pairs of hysterons with frustrated interactions, even within larger systems. Our work suggests that this enhanced memory is a signature of frustration, and establishes a generic principle for remembering asymmetric driving.