Slow Polarization and Depolarization Dynamics in a Single-Molecule Electret

Recently, single-molecule electrets (SMEs), which exhibit ferroelectric behavior within an individual molecule based on an intramolecular double-well potential associated with polarization, have been reported. However, their polarization dynamics have not yet been clarified, although they have attracted significant interest. In this study, the polarization and depolarization relaxation processes of Preyssler-type polyoxometalate K12[Tb3+⊂P5W30O110], which behaves as an SME, are analyzed by examining its charging and discharging currents. The results indicate that both processes exhibit relaxation behavior that can be described by the Kohlrausch–Williams–Watts (KWW) function. Subsequently, the double-well potential governing material polarization in the absence of an external electric field, as well as its asymmetrization under an applied field, is quantitatively evaluated based on the temperature dependence of the relaxation times of the charging and discharging currents obtained by fitting with the KWW function. Furthermore, it is demonstrated that polarization hysteresis emerges in an electric-field regime where the relaxation time of the discharging current exceeds that of the charging current. These results deepen the physical understanding of SMEs while also providing an important foundation for the design of new SMEs.