Uncovering Multiple Intrinsic Chiral Phases with Unexpected Properties in (PEA)₂PbI₄

We investigate the ground state of the benchmark (PEA)₂PbI₄ compound, using complementary information from low-temperature x-ray diffraction (XRD) and photoluminescence spectroscopy, combined with density functional theory calculations. We find four crystallographic configurations from low-temperature XRD, indicating a ground state with an intrinsic disorder stemming from two coexisting chiral sublattices, each with a bi-oriented organic spacer molecule. We further show evidence that these chiral structures form unevenly populated ground states, portraying uneven anharmonicity, where the state population may be tuned by surface effects. Importantly, our computational studies further reveal the presence of an intrinsic Rashba effect within some of the ground state phases, suggesting its overall existence despite the nominally centrosymmetric nature of the structure.