Design of Two-Dimensional\nHybrid Perovskites with\nGiant Spin Splitting and Persistent Spin Textures

Semiconductors with large energetic separation Δ<i>E</i><sup>±</sup> of energy sub-bands with distinct spin\nexpectation\nvalues (spin textures) represent a key target to enable control over\nspin transport and spin-optoelectronic properties. While the paradigmatic\ncase of symmetry-dictated Rashba spin splitting and associated spin\ntextures remains the most explored pathway toward designing future\nspin-transport-based quantum information technologies, controlling\nspin physics beyond the Rashba paradigm by accessing strategically\ntargeted crystalline symmetries holds significant promise. In this\npaper, we show how breaking the traditional paradigm of octahedron-rotation\nbased structure distortions in 2D organic–inorganic perovskites\n(2D-OIPs) can facilitate exceptionally large spin splittings (Δ<i>E</i><sup>±</sup> > 400 meV) and spin textures with\nextremely\nshort spin helix lengths (<i>l</i><sub>PSH</sub> ∼\n5 nm). A simple bond angle difference captures the distortion-driven\nglobal asymmetry and correlates quantitatively with first-principles\ncomputed spin-splitting magnitudes. A multiband effective mass model\nthat accounts for interlayer coupling provides a unified understanding\nof how specific symmetry elements dictate layer- and state-dependent\nspin polarizations within these multi-quantum-well structures. The\ngeneral symmetry analysis methodology presented here, together with\nthe potential for rationally creating 2D-OIPs with unique symmetry\npatterns, opens a pathway to design semiconductors with outstanding\nspin properties for next generation opto-spintronics.