Self-trapped carrier states and dielectric hysteresis in disordered dipole systems

Theory of self-trapped free-carrier states (fluctuons) at polarization fluctuations in KTaO₃:Li,Nb-type disordered ferroelectrics has been developed. The main characteristics of the fluctuon, viz. its energy, localization length, effective mass, and mobility have been calculated as functions of impurity-dipole concentration and temperature. The theory predicts the appearance of stable fluctuon states both in the ferroelectric-dipole-glass mixed phase and in the dipole glass state of disordered ferroelectrics. The possible participation of fluctuons in conduction and other transport phenomena in disordered ferroelectrics is discussed. Fiz. Tverd. Tela (St. Petersburg) 40, 722–727 (April 1998)