Inherent state memory as a probe for non-equilibrium Gardner physics in thermal soft spheres

The Gardner transition, located deep within the glass phase, denotes a topological change in the (effective) free energy landscape of a glass from smooth to rough. The saddle points inherent to this change lead to a marked dynamical slowdown and to growing correlation lengths. Until recently, the Gardner transition had only been characterized in equilibrium or quasi-equilibrium systems near jamming, and thus its experimental observation would have required enormous time scales and high instrumental accuracy. However, recent work has shown that Gardner-related signatures also emerge when a dense liquid or glass is rapidly quenched towards the nearest jammed configuration. In this talk, we demonstrate the existence of an out-of-equilibrium Gardner transition in a nearly-hard-sphere liquid that manifests in: (i) a divergence in the time required for energy minimization, (ii) the onset of a large susceptibility, and (iii) the onset of rattler identity changes. The last of these effects, in particular, should be experimentally accessible.