Strong Rashba-Dresselhaus Effect in Non-chiral 2D Ruddlesden-Popper Perovskites

Chirality transfer from organic chiral molecules to lead halides has been theorized as the origin of the strong Rashba-Dresselhaus effect causing large circular dichroism (CD) and circularly polarized luminescence (CPL) in metal halide perovskites (MHPs). Here, we provide a concrete empirical evidence that such strong CD and CPL can occur even in non-chiral 2D Ruddlesden-Popper perovskites (RPPs) such as in (BA)₂(MA)_n-1Pb_nI_3n+1 (where MA = CH₃NH₃ and BA = CH₃(CH₂)₃NH₃). The CD and CPL responses occuring at the excitonic transition of the MHPs are strongest (~100 mdeg and 4.8%, respectively) when a single lead halide octahedral [PbI₆]^4- layer is repeatedly stacked between two non-chiral molecules BA⁺ (n = 1). However, they are rapidly quenched as n increases. We hypothesize that strong Rashba-Dresselhaus splitting in the 2D RPPs originates the strong CD and CPL signatures. Density functional theory (DFT) calculations reveal that the large inter-layer distortions in the inorganic layers at the organic/inorganic interface gives raise to the strong Rashba-Dresselhaus splitting. A Rashba-Dresselhaus field of 600 mT and 50 mT for n = 1 and 2, respectively, are estimated by magnetic circular dichroism (MCD) spectroscopy. Our studies may have significant impact on designing 2D RPPs with large Rashba-Dresselhaus effects at room temperature for spintronic applications.