Stretched-exponential decay functions from a self-consistent model of dielectric relaxation

There are many materials whose dielectric properties are described by a stretched exponential, the so-called Kohlrausch–Williams–Watts (KWW) relaxation function. Its physical origin and statistical-mechanical foundation have been a matter of debate in the literature. In this Letter we suggest a model of dielectric relaxation, which naturally leads to a stretched exponential decay function. Some essential characteristics of the underlying charge conduction mechanisms are considered. A kinetic description of the relaxation and charge transport processes is proposed in terms of equations with time-fractional derivatives.