Interlayer Decoupling Growth for Atomically Thin Hybrid Perovskite Ferroelectrics with Giant Rashba Splitting Energy

Ferroelectric materials enable direct spin-to-charge conversion through the electrical switching of ferroelectric polarization, which is crucial for future spintronic devices. Particularly, hybrid perovskite ferroelectrics with atomically thin thickness introduce additional degrees of freedom, thereby improving spin-to-charge conversion efficiency. However, the atomically thin growth of these materials is challenging due to their intrinsic ionic character and low lattice formation energy, which leads to three-dimensional unordered growth. Herein, we establish an interlayer decoupling growth (IDG) strategy to achieve precise synthesis of atomically thin hybrid perovskite ferroelectrics. This strategy weakens the coordination between organic cations and inorganic layers, thereby promoting the in-plane anisotropic growth. Well-defined hybrid perovskite ferroelectrics with thickness from 2 to 7 unit cells (UC) are achieved by precise solvent tuning, offering a platform for studying their layer-dependent spin properties. Importantly, a giant Rashba spin-splitting energy E_R of 128 ± 20 meV was observed in atomically thin (CHA)₂PbBr₄ (CHA = cyclohexylammonium) owing to increased structural asymmetry. This work presents a strategy for synthesizing atomically thin hybrid perovskite ferroelectrics with giant Rashba spin-splitting energy, offering new classes of Rashba ferroelectric materials for future spin-orbitronic applications.