Unusual static and dynamical characteristics of domain evolution in ferroelectric superlattices

The evolution from nanostripes to monodomains is explored in ferroelectric BaTiO3/SrTiO3 (BT/ST) superlattices under dc and ac electric fields via the use of a first-principles-based technique. Such evolution involves original states that result in the decoupling of (static and dynamical) properties between BT versus ST layers. For instance, domain walls of nanostripes move at a different speed inside BT versus ST layers, and one intermediate state consists of three-dimensional nanobubbles inside BT layers coexisting with a monodomain inside ST layers. Moreover, velocities of domain walls of nanostripes and nanobubbles are determined as a function of the magnitude and frequency of the applied electric field. The domain-wall motion in BT and ST layers is found to follow a previously determined equation at small fields. On the other hand, velocities of domain walls of nanostripes and nanobubbles are found to obey a different empirical law at higher fields.