Intrinsic Rashba Effect in Stable Configurations of Two-Dimensional (PEA)₂PbI₄

Halide perovskites (HPs) are crystalline solids that feature a unique softness, absent in conventional semiconducting materials. In recent years, this softness has been pivotal to many properties in these materials, in both static and dynamic regimes. Here, we focus on the two-dimensional (2D) (PEA)2PbI4 crystal. We employ extensive density functional theory calculations and structural analysis to uncover a rich mosaic of ground-state configurations, identifying several stable configurations with distinct electronic properties. Our study uncovers an intrinsic Rashba effect within a structure traditionally considered as globally centrosymmetric, presenting a challenge to conventional understanding in the field. The observed effect emerges from a local symmetry-breaking induced by specific spatial orientations of the organic PEA molecules. This intrinsic Rashba effect, observed in select configurations, underscores the nuanced symmetrical complexities of 2D HPs and highlights their potential for spin-related applications. Additionally, our investigation demonstrates the exceptional flexibility of 2D HPs, as evidenced by an observed significant tolerance toward single-molecule rotations. This flexibility suggests potential pathways for smoother transitions between different molecular domains within these materials. Overall, our findings emphasize the intricate interplay between the organic/inorganic counterparts and the electronic properties in 2D HPs, paving the way for further exploration and exploitation of their unique characteristics in various optoelectronic and spintronic applications.卤化物钙钛矿（Halide Perovskites，HPs）是一类兼具独特柔软性的结晶固体，而该特性在传统半导体材料中并不存在。近年来，这种柔软性在该类材料的静态与动态特性中均发挥了至关重要的作用。本文聚焦于二维（2D）(PEA)₂PbI₄晶体，通过大规模密度泛函理论（Density Functional Theory）计算与结构分析，揭示了其丰富的基态构型图谱，并鉴定出多种具备独特电子性质的稳定构型。本研究发现，在传统上被认为是整体中心对称的结构中，存在本征拉什巴效应（Rashba Effect），这对该领域的传统认知构成了挑战。该效应源于有机PEA分子特定空间取向所引发的局域对称性破缺。在特定构型中观测到的本征拉什巴效应，凸显了二维卤化物钙钛矿中微妙的对称复杂性，并彰显了其在自旋相关应用中的潜力。此外，本研究还证实了二维卤化物钙钛矿具备优异的结构灵活性：观测到其对单分子旋转具有极高的耐受性。这种灵活性为该类材料中不同分子畴域间的平滑过渡提供了潜在可行路径。总体而言，本研究结果强调了二维卤化物钙钛矿中有机/无机组分与电子性质之间的复杂相互作用，为进一步探索并利用其在各类光电子学与自旋电子学应用中的独特特性铺平了道路。