Dynamic correlations below structural phase transitions in weakly anisotropic systems

Abstract

Below the critical temperature of structural phase transitions dynamic behavior is studied along the longitudinal excitation branch in slightly anisotropic systems with an =3 component order parameter field. Exploiting the consequences of small deviations from isotropy and of the relatively high frequencies involved, it is found that a proportionality between the longitudinal excitation frequency and the order parameter can be expected to hold also beyond the static mean field temperature region. The applicability of the theory to certain perovskites is briefly discussed.