CRITICAL-DYNAMICS OF DIPOLAR GLASSES

We discuss the critical dynamics of dipolar glasses as observed in the dynamic dielectric response and the dynamic structure factor. Our ana lysis is based on a hydrodynamic model, generalized to include slow (d ipolar) fluctuations near the glass transition. The critical slowing-d own of the dipoles gives rise to anomalies in the dynamic dielectric r esponse, the appearance of a central peak and a divergent sound dampin g. All three phenomena are interrelated and determined by the critical exponents of an Ising spin glass. We work out the consequences of a d ynamic scaling hypothesis for the dipolar autocorrelation and discuss two examples of such a scaling function. One is calculated within mean -field theory and the other is taken from numerical simulations. We co mpare our results to recent experiments on (NH4I)(x)(KI)(1-x).