Low-temperature structural phase transitions: Phonon-like and relaxation order-parameter dynamics

Abstract

A theoretical study on low-temperature structural phase transitions is presented, in which both phonon-like and relaxation order-parameter dynamics are contemplated. While the first limiting case has been considered previously, the second one is studied here. Attention is put on the low-temperature asymptotics of the temperature dependence of the generalized susceptibility. In the relaxation case, it is found $\ensuremath{\sim}{({T}^{2}\ensuremath{-}{T}_{c}^{2})}^{\ensuremath{-}1}$ for temperature-independent relaxation times in a broad region of the temperature-pressure phase diagram. In contrast to that obtained in the phonon-like case, this asymptotics is not modified by long-range interactions (dipolar forces, piezoelectric effect, etc.).