Glassy aging with modified Kohlrausch-Williams-Watts form.

ABSTRACT

In this paper, we address the question of whether aging in the nonequilibrium glassy state is controlled by the equilibrium alpha-relaxation process, which occurs at temperatures above T(g) . Recently, Lunkenheimer [Phys. Rev. Lett. 95, 055702 (2005)] proposed a model for the glassy aging data of dielectric relaxation using a modified Kohlrausch-Williams-Watts form exp[-(t(age)/tau(age)(beta(age))] . The aging time t(age) dependence of the relaxation time tau(age) is defined by these authors through a functional relation involving the corresponding frequency nu(t(age))=1/(2pi tau(age)) , but the stretching exponent beta(age) is the same as beta(alpha), the alpha-relaxation stretching exponent. We present here an alternative functional form for tau(age)(t(age)) directly involving the relaxation time itself. The proposed model fits the data of Lunkenheimer perfectly with a stretching exponent beta(age) different from beta(alpha) .