Collective Motion in Superionic Conductors–Transverse Conductivity and Polaritons–

Abstract

The frequency and wave number dependent transverse conductivity of α-AgI type superionic conductors is calculated by using a continuum model. The anion cage is supposed to be immersed in the cation liquid. A short-range viscoelastic force as well as the Coulomb interaction is taken into account as the anion-cation interaction. The calculated conductivity, which satisfies the sum rule, reproduces the main features of the experimental results. The spectral density function and the dispersion relation of polaritons are also computed. It is shown that the latter is much similar to that in ordinary ionic crystals except that phonons are much damped.