Photostrictive two-dimensional materials in the monochalcogenide family

Abstract

Photostriction is predicted for SnS and SnSe monolayers, two-dimensional ferroelectrics with rectangular unit cells (the lattice vector ${\mathbf{a}}_1$ is larger than ${\mathbf{a}}_2$) and an intrinsic dipole moment parallel to ${\mathbf{a}}_1$. Photostriction in these two-dimensional materials is found to be induced by a screened electric polarization in the photoexcited electronic state (i.e., a converse piezoelectric effect) that leads to a compression of $a_1$ and a comparatively smaller increase of $a_2$ for a reduced unit cell area. The structural change documented here is ten times larger than that observed in BiFeO${}_3$, making monochalcogenide monolayers an ultimate platform for this effect. This structural modification should be observable under experimentally feasible densities of photexcited carriers on samples that have been grown already, having a potential usefulness for light-induced, remote mechano-opto-electronic applications.

5 pages, 4 figures, one Table