Effective photon exchange correlations in ferroelectrics

Abstract

We propose a photon correlation theory for ferroelectrics especially focused on KDP-type where we consider a photon field from its constituent electrons and ions. We derive a Curie-Weiss type dielectric susceptibility from the microscopic Hamiltonian and we obtain the ferroelectric transition temperature, T-c. We calculate the free energy by applying the bosonic operator formalism to the Hamiltonian. A linear temperature-dependent specific heat C-upsilon conforming with experimental data for some ferroelectric materials is obtained. We calculate the isotope exponent, alpha, on T-c. We also derive phonon dispersion relations in the presence of electron-phonon interactions to show soft modes at T-c.