Dynamic correlations below the anti-ferrodistortive transition in perovskites

Abstract

Abstract Dynamic behavior in certain perovskites below the anti-ferrodistortive transition is studied along the longitudinal excitation branch by investigating effects of weak anisotropy for a n = 3 component order parameter field. Exploiting the consequences of small deviations from isotropy and of the relatively high frequencies involved, it is found that the longitudinal excitation frequency ωL may be expected to be proportional to the average value P of the order parameter beyond the static mean-field region of temperatures. Experimental implications of our theory are briefly discussed.