Temperature behaviour of solitons in ferroelectrics of the order-disorder type

Abstract

The temperature dependence of ferroelectric soliton characteristics is analysed. Ferroelectric solitons appearing as a result of the interaction between quasispins and mechanical oscillations are investigated. An equivalent temperature-dependent Hamiltonian of the system containing ferroelectric excitations, phonons and the interaction of phonons with quasispin excitations is formulated. This Hamiltonian includes the ordering parameter of the quasispin subsystem and the temperature-dependent force constant controlling the behaviour of the mechanical oscillations. The wave functions and energies belonging to ferroelectric solitons are derived. It is shown that the soliton effect is more pronounced at low temperature, whereas in the neighbourhood of the transition temperature, the energies of ferroelectric solitons and of normal soliton excitations become very close and differ only by a negligible amount. © 1988.