Aging in spin glasses is analyzed via the probability density function (PDF) of the heat transfer over a short time δt between system and heat bath. The PDF contains a Gaussian part, describing reversible fluctuations, and an exponential "intermittent" tail. We find that the relative weight of these two parts depends, for fixed δt, on the ratio of the total sampling time t to the age tw. Fixing this ratio, the intensity of the intermittent events is proportional to δt/tw and independent of the temperature. The Gaussian part has a variance with the same temperature dependence as the variance of the equilibrium energy in a system with an exponential density of states. All these observations are explained assuming that for any tw, intermittent events are triggered by local energy fluctuations exceeding those previously occurred.
EPL (Europhysics Letters)
- Pub Date:
- February 2005
- Condensed Matter - Soft Condensed Matter;
- Condensed Matter - Statistical Mechanics
- 7 pages, 4 figs Final, extended version to appear in Europhysics Letter