Superconductors and multiferroics are two of the hottest branches in condensed matter physics. The connections between those two fields are fundamentally meaningful to unify the physical rules of correlated electrons. Recently, BaFe2Se3, was predicted to be multiferroic [Phys. Rev. Lett. 113, 187204 (2014)] due to its unique one-dimensional block-type antiferromagnetism. Here, another iron-selenide KFe2Se2, a parent state of iron-based superconductor, is predicted to be multiferroic. Its two-dimensional block-type antiferromagnetism can generate a moderate electric dipole for each Fe-Se layer via the Fe-Se-Fe exchange striction. Different stacking configurations of these magnetic blocks give closely proximate energies and thus the ground state of KFe2Se2 may be switchable between antiferroelectric and ferroelectric phases.
@article{arxiv.1609.02614,
title = {Block antiferromagnetism and possible ferroelectricity in KFe$_2$Se$_2$},
author = {Yang Zhang and Huimin Zhang and Yakui Weng and Lingfang Lin and Xiaoyan Yao and Shuai Dong},
journal= {arXiv preprint arXiv:1609.02614},
year = {2016}
}