Phenomenological phase field modeling of monolayer ferroelectrics FEβ-In2Se3

Recently, a number of two-dimensional van der Waals (vdW) ferroelectrics have been reported, showing the potential to develop various ultra-thin smart devices down to the atomic monolayer limit. In particular, they have been demonstrated to exhibit intriguing polar domain structures. However, phenomenological thermodynamic models of vdW ferroelectrics, which can capture their ferroic domain structure evolution, are still lacking, limiting our further exploration of domain-structure-related applications. In this work, combining first-principles calculations, we construct a phenomenological phase field model for monolayer ferroelectrics, FEβ-In2Se3. Based on the model, one can calculate the phase stability, ferroelectric hysteresis curves, and domain structures of FEβ-In2Se3 under different loading conditions, showing the feasibility of electromechanically driving the rotation of in-plane polarization and manipulation of the domain structures. By including the second-order partial derivative gradient energy term, the model further captures well the antiferroelectric–ferroelastic domain structures of β′-In2Se3 observed in previous experiments. The developed phase field model should help better understand the domain structure evolution behavior in low-dimensional materials and promote further exploration of domain-structure-related applications.