Dynamic Stabilization of Metastable States in Triple-Well Ferroelectric Sn2P2S6

Polarization dynamics in ferroelectric materials is governed by the effective potential energy landscape of the order parameter. The unique aspect of ferroelectrics compared to many other transitions is the possibility of more than two potential wells, leading to complicated energy landscapes with new fundamental and functional properties. Here, direct dynamic evidence is revealed of a triple-well potential in the metal thiophosphate Sn2P2S6 compound using multivariate scanning probe microscopy combined with theoretical simulations. The key finding is that the metastable zero polarization state can be accessed through a gradual switching process and is stabilized over a broad range of electric fields. Simulations confirm that the observed zero polarization state originates from a kinetic stabilization of the nonpolar state of the triple-well, as opposed to domain walls. Dynamically, the triple-well of Sn2P2S6 becomes equivalent to antiferroelectric hysteresis loops. Therefore, this material combines the robust and well-defined domain structure of a proper ferroelectric with dynamic hysteresis loops present in antiferroelectrics. Moreover, the triple-well enhances mem-capacitive effects in Sn2P2S6, which are forbidden for ideal double-well ferroelectrics. These findings provide a path to tunable electronic elements for beyond binary high-density computing devices and neuromorphic circuits based on dynamic properties of the triple-well.

Automated summary

The polarization dynamics in ferroelectric materials depends on the potential energy landscape of the order parameter. Ferroelectrics have the unique property of having more than two potential wells, resulting in complex energy landscapes. In this study, the presence of a triple-well potential in the Sn2P2S6 compound was revealed using scanning probe microscopy and theoretical simulations. The metastable zero polarization state in Sn2P2S6 was accessed through a gradual switching process and was found to be stabilized over a wide range of electric fields. The observed zero polarization state originated from the kinetic stabilization of the nonpolar state of the triple-well.