The project is aimed to solving the fundamental scientific problem of the physics of nonequilibrium states associated with the study and description of the evolution of structures, including processes with significantly different timescales. As a model object, the evolution of the domains shape including the ultrafast domain walls kinetics during polarization reversal in ferroelectric lithium niobate single crystals will be studied. The scientific importance of the planned research is determined by the fact that the evolution of metastable structures, including ultrafast restructuring processes, will be studied in a homogeneous model system, the parameters of which will be controlled in a wide range, with visualization of the process with high time resolution. The practical importance of the problem is associated with the further development of methods for creation of regular ferroelectric domain structures with domain walls of arbitrary orientation, such as fan-out domain structures for highly tunable optical parametric oscillation and ring-shaped domain structures for diffractive optical elements.

The experimental study of the kinetics of the main types of domain walls in single crystals of the lithium niobate family will be conducted. The following fundamental tasks will be solved:

1) Experimental study of the formation and motion of ultrafast domain walls in single crystals of the lithium niobate family. Measurement of the kinetic Wulff plot for domain wall velocities.

2) Study of the dependence of the parameters of the kinetics of ultrafast domain walls on the magnitude of the external field.

3) Computer simulation of the domain shape evolution due to the formation and movement of ultrafast domain walls.

4) Investigation of the relationship between the evolution of the ultrafast domain wall and the shape of the corresponding switching current peak.

The proposed project is the first in the world practice systematic experimental study of the kinetics of ultrafast domain walls in model ferroelectric crystals of the lithium niobate family using a set of complementary methods. It should be noted that so far there are no experimental studies on the of kinetic Wulff plot in ferroelectrics. The principal moment in the project is the available experimental equipment and experience in in situ visualization of the domain structure kinetics with a time resolution down to 12 us. An original computer simulation of the domain shape evolution will be carried out taking into account the formation and movement of ultrafast domain walls based on the experimental measured kinetic Wulff plot.