Unique Pathways of Sliding Ferroelectricity in Few-Layered SnP₂Se₆ with Ultrahigh Carrier Mobility: A First-Principles Study

Understanding the transition pathway and relevant properties of sliding ferroelectricity presents a fascinating research frontier. Here, the ferroelectric and carrier behaviors of the few-layered SnP2Se6 were systematically investigated by the first-principles theory. It shows that the bilayer SnP2Se6 stabilizes in two degenerate minima, corresponding to AB- and AC-stackings, but with a reversal dipole moment, showing potential in sliding ferroelectricity. Unlike a conventional sliding procedure, a new transition mechanism can be found through a global surface potential search, along with a barrier four times lower than that through direct transition. Especially, a high tunneling electro-resistance (TER) ratio of 1.0 × 1013% at finite bias, as well as a relatively high carrier mobility, can be found in the bilayer case. Increasing thickness enables a significant enhancement of polarization and carrier mobility. Unexpectedly, the disparity of a electron and hole carriers can be linearly increasing to a rather high value of 12.31 for N = 6, showing potential in prohibiting carrier recombination. The analysis reveals that this unique behavior is strongly related to the elastic modulus and effective mass. Our findings exhibit the promising potential of few-layered SnP2Se6 for sliding ferroelectricity applications.