Ferroelectric (FE) size effects against the scaling law were reported recently in ultrathin group-IV monochalcogenides, and extrinsic effects (e.g. defects and lattice strains) were often resorted to. Via first-principles based finite-temperature (T) simulations, we reveal that these abnormalities are intrinsic to their unusual symmetry breaking from bulk to thin film. Changes of the electronic structures result in different order parameters characterizing the FE phase transition in bulk and in thin films, and invalidation of the scaling law. Beyond the scaling law Tc limit, this mechanism can help predicting materials promising for room-T ultrathin FE devices of broad interest.
@article{arxiv.1805.05055,
title = {A ferroelectric problem beyond the conventional scaling law},
author = {Qi-Jun Ye and Zhi-Yuan Liu and Yexin Feng and Peng Gao and Xin-Zheng Li},
journal= {arXiv preprint arXiv:1805.05055},
year = {2018}
}