Long-range current-induced spin accumulation in chiral crystals

The chirality-induced spin selectivity (CISS) refers to a conversion between charge and spin currents occurring in chiral molecules and solids, which reveals a great potential for applications in various areas of technology. Nevertheless, after two decades of studies, the understanding of its microscopic origin remains elusive. Here, the CISS effect in materials with strong spin-orbit coupling is explained in terms of the unconventional current-induced spin accumulation, an analog of the Rashba-Edelstein effect that may manifest in systems with a radial spin texture reversing the sign for opposite enantiomers. The calculations of spin accumulation based on the density functional theory, performed for the first time for Te and TaSi$_2$, provide a rationale for the experimental studies reporting CISS in these materials. The analysis of a general Weyl-type spin-orbit coupling locally describing the spin texture at specific momentum vectors, reveals that a quasi-persistent spin helix emerges in the real space as a consequence of the crystal symmetries, and prevents the spins from decoherence, which qualitatively supports the observation of the long-range spin transport in CISS experiments. These results open the perspectives for DFT calculations of CISS for any chiral crystals and represent a step forward to its understanding in general systems.