Ferroelectricity (Valasek, J. Phys. Rev. 1921, 17, 475) - a spontaneous formation of electric polarisation - is a solid state phenomenon, usually, associated with ionic compounds or complex materials. Here we show that, atypically for elemental solids, few-layer graphenes can host an equilibrium out-of-plane electric polarisation, switchable by sliding the constituent graphene sheets. The systems hosting such effect include mixed-stacking tetralayers and thicker (5-9 layers) rhombohedral graphitic films with a twin boundary in the middle of a flake. The predicted electric polarisation would also appear in marginally (small-angle) twisted few-layer flakes, where lattice reconstruction would give rise to networks of mesoscale domains with alternating value and sign of out-of-plane polarisation.
@article{arxiv.2305.10896,
title = {Mixed-Stacking Few-Layer Graphene as an Elemental Weak Ferroelectric Material},
author = {Aitor Garcia-Ruiz and Vladimir Enaldiev and Andrew McEllistrim and Vladimir I. Fal'ko},
journal= {arXiv preprint arXiv:2305.10896},
year = {2023}
}