Predicting two-dimensional ferroelastic semiconductors LuX (X=N, P, As): negative poisson's ratio, high carrier mobility, and strong visible light absorption

Abstract Two-dimensional (2D) materials manifesting ferroelasticity have received significant attention, yet it is uncommon for single materials to exhibit ferroelasticity alongside high carrier mobilities and strong visible light absorption. In this study, we use first-principles calculations to predict three 2D semiconductors: LuX monolayers (X = N, P, As), which are distinguished by their exceptional dynamical, thermodynamic, and mechanical stability. These LuX monolayers feature band gaps ranging from 0.98 eV to 1.98 eV, placing them within the ideal range for solar cell applications, and they exhibit strong visible light absorption, reaching up to 5%. Notably, the LuP monolayer demonstrates remarkable carrier mobility, reaching 1796 cm²·s⁻¹·V⁻¹, surpassing that of MoS₂ and showcasing its superior transport properties. Mechanical analyses reveal a significant in-plane negative Poisson's ratio (NPR) for these materials, as high as -0.37, which is substantially greater than that of black phosphorus. Additionally, all LuX monolayers are identified as 2D ferroelastic materials, with reversible strains ranging from 12.9% to 17.8%. Our findings highlight the exceptional electronic, mechanical, and optical properties of the LuX monolayers, making them promising candidates for a wide range of multifunctional applications.