Sliding and superlubric moiré twisting ferroelectric transition in HfO₂

Despite progress in HfO₂ thin-film ferroelectrics, issues like high coercive fields persist, and the dynamics of twisted ferroelectricity remain largely unexplored. Here, we explore how sliding and twisting in bilayer HfO₂ enables low barrier switching. Among 144 sliding configurations, two exhibit strong in-plane polarization (2360 pC/m) with a low switching barrier of 9.57 meV/f.u. Twisting generates polar textures associated with moiré patterns, which drive ferroelectricity via a soft zone-center mode, as revealed by machine-learning-assisted first-principles calculations. The in-plane (out-of-plane) polarization values for HfO₂ at twist angles of 21.79°, 27.80°, and 46.83° are 430 (5.82), 367 (2.20), and 1057 (0.03) pC/m, respectively. For 21.79° and 27.80° twisting, switching barriers drop to 1.74 and 0.18 meV/f.u., indicating superlubric-like transitions. Notably, the 46.83° twisted bilayer shows an almost barrier-free polar evolution (0.03 meV /f.u.), attributed to sharply enhanced zone-center phonon linewidths. Our findings establish a moiré-engineered switching route for 2D ferroelectrics.