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