Chirality induced spin selectivity in chiral crystals

Abstract

Chirality is a fundamental property of great importance in physics, chemistry, and biology, and has recently been found to generate unexpected spin polarization for electrons passing through organic molecules, known as chirality-induced spin selectivity (CISS). CISS shows promising application potential in spintronic devices, spin-controlled chemistry, and enantiomer separation. It focuses on organic molecules that exhibit poor electronic conductivity and inherent complexities, such as the debated role of SOC at the molecule-metal interface. In this work, we go beyond organic molecules and study chiral solids with excellent electrical conductivity, intrinsic SOC, and topological electronic structures. We demonstrate that electrons exhibit both spin and orbital polarization as they pass through chiral crystals. Both polarization increases with material thickness before saturating to the bulk values. The spin polarization is proportional to intrinsic SOC while the orbital polarization is insensitive to SOC. The large spin polarization comes with strong electrical magnetochiral anisotropy in the magneto-transport of these chiral crystals (e.g., RhSi). Our work reveals the interplay of chirality, electron spin, and orbital in chiral crystals, paving the way for developing chiral solids for chirality-induced phenomena.