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.