Elasticity of two-dimensional ferroelectrics across their paraelectric phase transition*

Two-dimensional (2D) ferroelectric SnSe monolayers turn paraelectric at finite temperature due to an effective increase in atomistic coordination at their ferroelectric-to-paraelectric transition, whereby the structure turns from a three-fold coordination onto an average five-fold coordination, and from a rectangular unit cell onto a square one.  Current understanding for elasticity only looks at zero-temperature structures, and it tends to neglect the strong non-linear mechanical behavior of this material that even leads to phase transitions.  In this presentation, we propose a model to estimate the elastic moduli at finite temperature and across the structural transition.