Heat capacity and thermal transport revisited in displacive ferroelectrics

The collective excitation in displacive ferroelectrics, so called ferron, describes polarization fluctuations and exhibits a low excitation energy at long-wavelength limit. Essential contribution of this excitation to thermal properties can therefore be expected. Here, we study the temperature and external electric-field dependence of the ferron contribution to heat capacity and thermal transport, by incorporating the self-consistent renormalization theory of the phase transition of displacive ferroelectricity. We consider PbTiO₃ as specific application, and the produced results can quantitively capture the experimental measurement. These findings offer unexpected prospects for the interplay between polarization fluctuations and thermal transport in ferroelectrics materials.