All-Electrical Control of Shift Current and Persistent Spin Textures in Two-Dimensional Ferroelectric Ruddlesden–Popper Perovskites

Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) are promising materials for optoelectronic and spintronic applications. Using first-principles calculations combined with irreduciblerepresentation decomposition and wave-vector point-group symmetry analysis, we investigate three C_2 \mathrmv-symmetric Ruddlesden-Popper ferroelectric perovskites, (4,4-\mathrmDFPD)_2 \mathrmPbI_4,(\mathrmDFCHA)_2 \mathrmPbI_4, and PEPI, together with monoclinic (4,4-\mathrmDFHHA)_2 \mathrmPbI_4 in lower C_2 symmetry. The sizable shift-current (SC) responses up to 69.16 \mu \mathrm~A / \mathrmV^2 are predicted in PEPI, an order of magnitude larger than those of conventional ferroelectric oxides. Among the orthorhombic 2D perovskites with C_2 \mathrmv point group, SC shows an empirical positive correlation with the local octahedral bond-length distortion index D_i. However, (4,4-\mathrmDFHHA)_2 \mathrmPbI_4 exhibits a large D_i but a comparatively small SC response. Bondresolved COHP/ICOHP analysis reveals weakened and strongly differentiated Pb-I bonding in this compound, demonstrating that local structural distortion and bonding-induced orbital hybridization must be considered to rationalize the variation in SC. The symmetry-protected persistent spin textures (PSTs) in those C_2 \mathrmv Perovskites are favorable for suppressing spin dephasing and potentially achieving long spin lifetimes and transport distances. Although the reduced C_2 symmetry cannot accommodate the ideal PST, (4,4-\mathrmDFHHA)_2 \mathrmPbI_4 retains a quasi-PST and may therefore hold these spin-transport advantages. Ferroelectric polarization switching can reverse the SC direction and the spin textures under the incident light, indicating the advantage for nonvolatile, all-electrical control of both shift current and spin current responses. Finally, we propose practical criteria for evaluating material with potential PST, including spin-splitting coefficients, momentum-space coverage, suitable band gaps, and the Curie temperatures of the host ferroelectric phases. Our work provides the guidance for designing high-performance multifunctional spintronic-photovoltaic materials and devices.