Solitons and critical breakup fields in lithium niobate type uniaxial ferroelectrics

Ferroelectric materials, such as lithium niobate, show interesting non-linear hysteresis behavior that can be explained by a dynamical system analysis. By using variational principle, a non-linear Klein-Gordon (K-G) equation is derived for lithium niobate type of uniaxial ferroelectrics involving various types of energy, which was not considered previously to construct the Hamiltonian. This leads to soliton solutions under different conditions of soliton velocity. The critical value of the (dimensional) effective electric field has been estimated to be 54-58 kV/cm for lithium niobate depending on the impurity content in these type inhomogeneous ferroelectrics. Beyond this critical field, there is no existence of solitons. This critical field is related to a break-up mechanism of Landau-Ginzburg two-well potential to a single well, as the driving force is increased.