From Subaging to Hyperaging in Structural Glasses

Abstract

We demonstrate nonequilibrium scaling laws for the aging and equilibration dynamics in glass formers that emerge from combining a relaxation equation for the static structure with the equilibrium scaling laws of glassy dynamics. Different scaling regimes are predicted for the evolution of the structural relaxation time τ with age (waiting time tw), depending on the depth of the quench from the liquid into the glass: "simple" aging (τ∼tw) applies for quenches close to the critical point of mode-coupling theory (MCT) and implies "subaging" (τ≈tδw with δ<1) as a broad equilibration crossover for quenches to nearly arrested equilibrium states; "hyperaging" (or superaging, τ∼tδ′w with δ′>1) emerges for quenches deep into the glass. The latter is cut off by non-mean-field fluctuations that we account for within a recent extension of MCT, the stochastic β-relaxation theory (SBR). We exemplify the scaling laws with a schematic model that quantitatively fits simulation data.