Origin of Rashba Spin Splitting and Strain Tunability in Ferroelectric Bulk CsPbF₃

Spin–orbit coupling (SOC) in conjunction with broken inversion symmetry acts as a key ingredient for several intriguing quantum phenomena, viz., persistent spin textures, topological surface states and Rashba–Dresselhaus (RD) effect. The coexistence of spontaneous polarization and the RD effect in ferroelectric (FE) materials enables the electrical control of spin degrees of freedom. Here, we explore the FE lead halide perovskite CsPbF₃ as a potential candidate in the field of spintronics by employing state-of-the-art first-principles-based methodologies, viz., density functional theory (DFT) with semilocal and hybrid functional (HSE06) combined with SOC and many-body perturbation theory (G₀W₀). For a deeper understanding of the observed spin splitting, the spin textures are analyzed using the k.p model Hamiltonian. We find there is no out-of-plane spin component indicating that the Rashba splitting dominates over Dresselhaus splitting. Owing to the presence of Pb-6p orbital in conduction band, the large value of Rashba coefficient (α_R) at conduction band minimum (CBm) is noticed in comparison to that of at the valence band maximum (VBM). We also observe that the strength of Rashba spin splitting can be substantially tuned on application of uniaxial strain (±5%). More interestingly, we notice reversible spin textures by switching the FE polarization in CsPbF₃ perovskite, making it potent for perovskite-based spintronic applications.