Vector, bidirector, and Bloch skyrmion phases induced by structural crystallographic symmetry breaking

Abstract

The 212 species of structural phase transitions which break macroscopic symmetry are analyzed with respect to the occurrence of time-reversal-invariant vector and bidirector order parameters. The possibility of discerning the orientational domain states of the low-symmetry phase by these ``vectorlike'' physical properties has been derived using a computer algorithm exploiting the concept of polar, axial, chiral, and neutral dipoles. It is argued that the presence of a pseudo-Lifshitz invariant of chiral bidirector symmetry in a Ginzburg-Landau functional of uniaxial ferroelectrics can induce electric Bloch skyrmions in the same way as the Dzyaloshinskii-Moriya interaction induces bulk magnetic Bloch skyrmions in chiral magnets. It is found that this is possible for three types of fully ferroelectric phase transitions with a chiral paraelectric phase.