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, Tc. We calculate the free energy by applying the bosonic operator formalism to the Hamiltonian. A linear temperature-dependent specific heat Cv conforming with experimental data for some ferroelectric materials is obtained. We calculate the isotope exponent, α, on Tc. We also derive phonon dispersion relations in the presence of electron-phonon interactions to show soft modes at Tc.