C. Brun, F. Ladieu, L'Hôte, G. Biroli, Jean-Philippe Bouchaud
We have measured, as a function of the age $t_a$, the aging of the nonlinear dielectric susceptibility $\chi_3$ of glycerol below the glass transition. Whereas the linear susceptibility can be accurately accounted for in terms of an age dependent relaxation time $\tau_{\alpha}(t_a)$, this scaling breaks down for $\chi_3$, suggesting an increase of the amplitude of $\chi_3$. This is a strong indication that the number $N_{corr}$ of molecules involved in relaxation events increases with $t_a$. For $T=0.96 \times T_g$, we find that $N_{corr}$ increases by $\sim 10%$ when $t_a$ varies from $1\mathrm{ks}$ to $100\mathrm{ks}$. This sheds new light on the relation between length scales and time scales in glasses.
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http://arxiv.org/abs/1209.3401
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