Strain-aided room-temperature second-order ferroelectric phase transition in monolayer PbTe: Deep potential molecular dynamics simulations

The discovery of room-temperature monolayer ferroelectrics (FEs) holds significant promise for advancing the development of nanoscale functional devices. Although the ab initio calculations have demonstrated the strain-induced ferroelectricity of two-dimensional (2D) PbTe, the structural and thermodynamic characteristics of this ferroelectric phase transition at larger temporal and spatial scales remain unexplored. Molecular dynamics (MD) is an effective tool to use to address this question. However, the lack of an appropriate force field has hindered progress. Here, we have developed an interatomic potential for 2D PbTe based on the deep potential framework, enabling MD simulations with ab initio-level accuracy to investigate the FE phase transition. Our MD results demonstrate robust ferroelectricity at room temperature in adequately strained 2D PbTe, which remains paraelectric at lower temperatures. Structural analyses indicate that the FE transitions are displacive, highlighting the strong coupling between the strain condition and the polarization state. Furthermore, we established a phase diagram of 2D PbTe in the temperature-strain space, guiding the tunable phase transition temperature with the aid of prestrains. Finally, the second-order transition nature of FE transition in 2D PbTe is observed, suggesting the potential utilization of a new room-temperature, nonhysteresis 2D ferroelectric material.