Fig. 1. (a) Schematic illustration of the anomalous transverse spin OT induced by chirality transfer (depicted by the sky-blue curved arrow) from a chiral particle to a gold sphere. The dimer system is excited by a pair of counter-propagating linearly polarized plane waves with identical polarization states. The green double arrow represents an electric field polarized along the y-direction, while the dark blue double arrow represents polarization along the x-direction. It observes the variation of the transverse spin OT as a function of the position xAu of the gold sphere when it is placed to the (b) left and (c) right of the chiral particle.

Fig. 2. The physical origin of chirality-transfer-induced transverse spinning motions of achiral particles. The relationship between the location xAu of gold sphere and the exerted transverse spin OT, along with its components associated with the electric and magnetic dipole moments as described in Eq. (12) (a), (c), or the electric and magnetic SAM densities as described in Eq. (19) (b), (d). The system is excited by counter-propagating fields with (a), (b) x-polarization and (c), (d) y-polarization. The transverse spin OT TxFW based on full-wave calculation (black circle) is also plotted for comparison. The symbol ×0.1 indicates that the respective values have been scaled by a factor of 10 for better visualization.

Fig. 3. Local transverse SAM arises from the contribution of chirality transfer. For excitation light with (a), (b) x-polarization and (c), (d) y-polarization, the normalized x-component of the SAM density and its electric and magnetic contributions, as well as the components based on Eqs. (21) and (22) as a function of the chirality parameter κ of the particle.

Fig. 4. Effects of chirality-transfer-induced transverse spin OT on achiral particles under excitation light with (a), (c) x-polarization and (b), (d) y-polarization. (a), (b) The transverse spin OT and its decomposition terms as functions of the chirality parameter κ of the particle. The transverse spin OT TxFW based on full-wave calculations (circle) and Txb (triangle) and Txa (diamond) based on simplified derivation are also plotted for comparison. (c) The transverse magnetic spin OT and (d) electric spin OT as functions of the separation distance g of the dimer system and the radius of the gold particle.

Fig. 5. (a) Transverse OT exerted on a gold nanoparticle with a fixed radius of RAu=80  nm, plotted as a function of the radius of a nearby chiral particle. The gold nanoparticle is positioned at xAu=3.5  μm. (b) Transverse OT on the same gold nanoparticle as a function of the chirality parameter κ of the chiral particle, whose radius is either 500 nm (black dashed line) or 80 nm (red line). The permittivity and permeability of the chiral particle are fixed at εc=2.53 and μc=1, respectively. The surface-to-surface separation between chiral and gold dipole particles is 90 nm.

Fig. 6. The chirality-transfer-induced transverse spin OT on various types of achiral particles under excitation light with (a) x-polarization and (b) y-polarization. The symbol ×100  (×10) indicates that the respective values have been magnified by a factor of 100 (10) for better visualization.

Fig. 7. Electric and magnetic contributions to chirality-transfer-induced transverse spin OTs for Au (left column), Si (middle column), and Ge (right column) spheres. The spectrum of (a)–(c) the transverse spin OT, (d)–(f) the parameters related to the Mie coefficients, and (g)–(i) the normalized x-component of the local SAM density at the location of the achiral sphere. The red solid lines and blue dashed lines represent electric and magnetic quantities, respectively. Resonances facilitating electric or magnetic chirality transfer are marked by magenta and green dashed lines.