Competing time scales at the ferroelectric phase transition

Abstract

The order of the ferroelectric phase transition is investigated using two different methods. i) A molecular dynamics study of the two-dimensional nonlinear polarizability model; ii) An investigation of exact solutions of the one-dimensional analogue of the same nonlinear model. Both methods clearly show that, in the vicinity of the ferroelectric phase transition temperature, T _c the particle dynamics are governed by two different time scales, one reflecting order-disorder dynamics while the other corresponds to classical mode softening. Even though order-disorder effects always govern the dynamics very close to T _c , their onset strongly depends on the mass ratio of the constituting ions, the anharmonicity of the system and the time scale used to investigate the material.