Mobility of phase solitons in polar commensurate phase

Dynamics of phase solitons in the polar commensurate phase is analysed in the framework of the phenomenological model usually used to describe the commensurate-incommensurate phase transition of the first kind, assuming the continuous order parameter and the constant amplitude approximation. Comparison with domain walls in the usual ferroelectric phase is provided. While the mobility of a usual ferroelectric domain wall diverges at the continuous phase transition to the disordered state, soliton mobility remains finite at the commensurate-incommensurate phase transition.