Various Possible Forms of Absolute-Type Ferroelectro-Incommensurateness
itsiro Aizu · Journal of the Physical Society of Japan · 1988
Phases that are incommensurate but yet also ferroelectric are possible, A ferroelectric incommensurate phase of the absolute type is defined as an incommensurate phase in which the relation P = f (| Q α | 2 , | Q β | 2 , | Q γ | 2 , …) holds and which has P 0 ≠0 through this relation. Here P denotes a polarization component; P 0 is its spatial average; Q α , Q α * , Q β etc. compose a degenerate set of order parameters; f is a function of only the absolute magnitudes (not depending on the arguments) of the order parameters. No possible specific forms of the above function have been known, except the simplest form P = J (| Q α | 2 -| Q β | 2 ), where J is a mere coefficient. The present paper shows a variety of specific forms and the cases where they occur. Some of these cases are particularly discussed.