Numerical Study on Aging Dynamics in Ising Spin-Glass Models: Temperature-Change Protocols

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By means of Monte Carlo simulations on the three-dimensional Ising spin-glass model, we have studied aging phenomena with various temperature(T)-change protocols. Particularly, a T-shift protocol, in which a system is first quenched to and aged for a period t w1 at a temperature T₁, and subsequently aged at a new temperature T₂ is closely investigated. Most importantly, the mean size of domains, which is extracted from the replica-overlap function, was found to grow monotonically without any appreciable decrease by the T-change. We also found the relaxation of energy density and spin auto-correlation function during the T-shift process can be explained within the following picture: the dynamics finally crossovers to an isothermal aging of T₂ at around t₂ ≃ t w1 (eff) after the T-change, where t w1 (eff) is an effective waiting time related with t w1, but in the transient regime t₂ t w1 (eff), adjustment of the population of thermally active droplets from that at T₁ to T₂ takes place very slowly. Implications of the results on aging phenomena in other T-change protocols such as T-cycling and continuous T-change with an intermittent stop observed by simulations as well as experiments are discussed.