Evidence of growing spatial correlations during the aging of glassy glycerol
C. Brun, F. Ladieu, L'Hôte, G. Biroli, Jean-Philippe Bouchaud
Abstract
We have measured, as a function of the age
t
a
, the aging of the nonlinear dielectric susceptibility
χ
3
of glycerol below the glass transition. Whereas the linear susceptibility can be accurately accounted for in terms of an age dependent relaxation time
τ
α
(
t
a
)
, this scaling breaks down for
χ
3
, suggesting an increase of the amplitude of
χ
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×
T
g
, we find that
N
corr
increases by
∼10
when
t
a
varies from
1ks
to
100ks
. This sheds new light on the relation between length scales and time scales in glasses.