Elucidating the Structure and Rashba/Dresselhaus Effect of Two-Dimensional Hybrid Organic–Inorganic Perovskites: The Role of Organic Cations

Two-dimensional hybrid organic-inorganic perovskites display strong spin-orbit coupling due to the presence of heavy elements. This results in pronounced Rashba-Dresselhaus splitting when inversion symmetry is broken. Nevertheless, the (PEA)₂PbI₄ (PEA = C₆H₅C₂H₄NH₃⁺) crystal with the centrosymmetric global space group exhibits a significant Rashba/Dresselhaus splitting, implying that the underlying mechanism responsible for inversion symmetry breaking in (PEA)₂PbI₄ is largely unexplored. Herein, we theoretically demonstrate that nominally centrosymmetric (PEA)₂PbI₄ shows a stable ground-state structure with local inorganic layer distortion connected with a specific orientation disparity of methyleneammonium moieties, which is driven by face-to-edge arrangement of phenyl groups. Subsequently, we quantitatively establish the correlation between local distortion and spin splitting, followed by disentangling different spin-orbit coupling coefficients from the complex spin texture. These findings emphasize the structures of (PEA)₂PbI₄ with local inversion symmetry breaking triggered by intricate interplays connecting with organic cations, paving the way for further exploration of their unique characteristics in spintronic applications.