Chirality Versus Symmetry: Electron's Spin Selectivity in Nonpolar Chiral Lead-Bromide Perovskites

In the last decade, chirality-induced spin selectivity (CISS), the spin-selective electron transport through chiral molecules, has been described in a large range of materials, from insulators to superconductors. Because more experimental studies are desired for the theoretical understanding of the CISS effect, chiral metal-halide semiconductors may contribute to the field thanks to their chiroptical and spintronic properties. In this regard, this work uses new chiral organic cations S-HP1A and R-HP1A (HP1A = 2-hydroxy-propyl-1-ammonium) to prepare 2D chiral halide perovskites (HPs) which crystallize in the enantiomorphic space groups P43212 and P41212, respectively. The fourfold symmetry induces antiferroelectricity along the stacking axis which, combined to incomplete Rashba-like splitting in each individual 2D polar layer, results in rare spin textures in the band structure. As revealed by magnetic conductive-probe atomic force microscopy (AFM) measurements, these materials show CISS effect with partial spin polarization (SP; +/- 40-45%). This incomplete effect is efficient enough to drive a chiro-spintronic device as demonstrated by the fabrication of spin valve devices with magnetoresistance (MR) responses up to 250 K. Therefore, these stable lead-bromide HP materials not only represent interesting candidates for spintronic applications but also reveal the importance of polar symmetry-breaking topology for spin selectivity. 2D chiral halide perovskites crystallizing in nonpolar enantiomorphic space groups present incomplete Rashba-like splittings of the bottom conduction and top valence bands, resulting in rare spin textures and chirality-induced spin selectivity. The electron's spin polarization in these stable thin films allows the fabrication of chiro-spintronic devices such as spin valves.image