Rashba-Related Spin-Selective Effect in 2D Chiral Perovskites with Achiral Organic Cation Spacers.

Abstract

Two-dimensional (2D) chiral perovskites offer a promising magnetic-field-free framework for spin-selective light-matter interactions. Yet, the influence of organic cations on Rashba-related spin effect has not been well comprehended. In this work, we demonstrate that the alloying of achiral and chiral spacers provides an efficient approach to modulating spin-selective phenomena in 2D chiral perovskites. Mixed-spacer films with achiral <i>n</i>-butylammonium spacers in a chiral methylbenzylammonium lattice exhibit enhanced chiroptical activity and spin-dependent optical responses compared the films with achiral or chiral organic cations. Based on the density functional theory and femtosecond circularly polarized transient absorption measurements, it is unveiled that spacer alloying perturbs the local structural environment and modifies Rashba-related band-edge asymmetry, resulting in a larger spin-selective transient response asymmetry and an enhanced optical Stark effect. It is elaborated that achiral-chiral spacer alloying can regulate Rashba-related spin-selective phenomena in 2D chiral perovskites and lead to coherent spin-optoelectronic functioning.