Deformation-driven modulation of chirality and spin polarization in L-cysteine intercalated MoS2 nanosheets: A mechanistic approach to chirality-induced spin selectivity in two-dimensional material

The electron spin represents an extra set of observables, and spin polarization has emerged as an important measurable for low-dimensional phenomena. Chirality-induced spin selectivity has emerged as a powerful strategy for generating spin-polarized currents without magnetic materials. Here, we demonstrate that controlled intercalation of chiral L-cysteine molecules into exfoliated MoS2 nanosheets at two different concentrations enables deformation-driven tuning of chirality and spin polarization. Notably, circular dichroism measurements show inversion of chiroptical response with molecular loading, which directly correlates with the sign and magnitude of spin polarization measured by using scanning tunneling spectroscopy. Density functional theory calculations reveal the structural-deformation dependence of the bandgap width and of the spin–orbit coupling splitting. The results establish a clear structure–chirality–spin relationship, where stacking-induced symmetry breaking governs spin-selective transport. This work provides a mechanistic framework for engineering chiral two-dimensional materials with tunable spin functionality for next-generation spintronic applications.