Effect of chirality on spin-polarization and conduction at a ferromagnetic interface

The chirality-induced spin-selectivity (CISS) effect has attracted significant interest for its potential in spintronic applications. However, the underlying mechanism behind CISS remains an open question. In this work, we systematically investigate inorganic chiral crystals placed on ferromagnetic substrates, with the aim to shed light on the source of the CISS effect. We focus on enantiomeric TM-Si₂ systems (TM: Transition Metal) and non-enantiomeric TMX systems (X: Al, Si, Ga), systematically varying the thickness of the materials by controlling the number of unit cells along the perpendicular direction. Using density functional theory (DFT), we explore the propagation of spin polarization in these systems. Additionally, we employ Landauer's approach to examine electron conduction through chiral substrates with magnetized electrodes. Our findings indicate distinct spin-polarization propagation patterns and spin-current characteristics depending on the material’s chirality and thickness. These results provide crucial insights into the role of structural chirality and the interface with ferromagnetic substrates in the manifestation of CISS. This study contributes valuable knowledge to the ongoing efforts of identifying the fundamental origin of the CISS effect, which could enhance the design of chiral materials for spintronic technologies.