Photonic spin-Hall effect in chiral plasmonic assemblies

Domain: physics
Published: 2026-02-26
Editorial outcome: minor_revision

Abstract
Directional light splitting based on the photonic spin-Hall effect is a desired feature for the development of spin-dependent optical elements. Here, we report on the routing of surface plasmon polaritons (SPPs) by using chiral gold nanocubes (AuNCs) and silver nanowires (AgNWs). We experimentally and theoretically observe the photonic spin-Hall effect in AgNWs under circularly polarized excitation and show that, when AuNCs of opposite chirality are attached to the NWs, linearly polarized illumination can modulate the SPPs formed on the NWs. We achieve directional emission of valley-polarized excitons from hybrid structures made of (chiral AuNC)–(AgNW) assembled with transition metal dichalcogenide monolayers and observe an enhanced degree of valley polarization. The underlying mechanism of the routing effect is understood through numerical simulations, confirming that the observed chirality-dependent routing effect can have important implications for the development of valleytronic circuits.

Introduction
The photonic spin-Hall effect is an optical phenomenon that demonstrates a correlation between the polarization of incident circularly polarized light (CPL) and the direction of excited evanescent waves1–3. One interesting result of this effect is the generation of unidirectional evanescent waves propagating in opposite directions with CPL of different handednesses. Spin-controlled directional light splitting has been achieved in both achiral plasmonic and dielectric waveguides under excitation of CPL4,5, which offers a versatile toolbox for efficient signal transmission and reception6, information encoding and retrieval7, and the construction of optical isolators and circulators for quantum optical applications8. However, there are still challenges to be addressed9. First, the output intensities at both ports of achiral waveguides are symmetric under linearly polarized excitation. Achieving robust directional transmission through asymmetric nanostructures thus becomes imperative when incident polarization is constrained to a fixed linear state. Second, precise manipulation of the near-field polarization state of light and its interaction with surface plasmon polariton (SPP) modes in plasmonic waveguides remains difficult. Chiral plasmonic nanostructures, which possess geometric properties that cannot be superposed on their mirror images, have emerged as a promising solution to address the aforementioned challenges10. A seed-mediated growth strategy has been developed to synthesize various chiral Au nanoparticles with controllable sizes and large extinction dissymmetry factors (g-factors) of 0.211–13. These chiral Au nanoparticles exhibit distinct interactions with left- and right-handed circularly polarized (LCP and RCP) light, enabling the modulation of the polarization of the surrounding electromagnetic field. Chiral nanoparticles can be assembled on the surface of a waveguide and used as spin-filters in routing devices. In addition, precise control over the plasmonic properties of chiral nanoparticles can be achieved by the design of their compositions and sizes. This enables efficient coupling of light to SPPs in the waveguide. Such a chirality-dependent manipulation method plays a crucial role in achieving desired routing performances and meeting specific application requirements. Assembling chiral plasmonic nanoparticles with nano-waveguides is therefore highly desirable, yet this important scenario has remained unexplored.

Chiral plasmonic nanostructures have been integrated with two-dimensional (2D) materials for the manipulation of their luminescent emissions, leveraging the plasmonic and chiroptical properties of chiral plasmonic nanostructures and the electronic and optical properties of 2D materials14. The recent discovery of 2D materials has provided rich opportunities to explore valley-polarized exciton emissions15. The combination of large spin splitting and time-reversal symmetry in transition metal dichalcogenide (TMDC) monolayers leads to opposite signs of spin splitting in the +K and −K valleys. This property enables the selective pumping of electrons into specific valley and spin states using LCP and RCP light in plasmon–exciton hybrid nanostructures16,17. Such a valley-dependent optical selection rule results in valley-polarized exciton emissions with particular circular polarization states18. Researchers have utilized chiral plasmonic nanostructures to tailor the valley-polarized photoluminescence (PL) in TMDC monolayers at room temperature19–21. The foundations are mainly based on two points. First, chiral plasmons can be used to reshape the polarization state of the electromagnetic field at TMDC monolayers. The pumping probability of electrons in one valley can be selectively enhanced or suppressed by the chiral electromagnetic field through the interaction between plasmons and excitons. Second, the Purcell effect induced by chiral plasmons can reduce the recombination lifetime of excitons and effectively increase the quantum yield of an emitter while keeping the valley scattering time unaffected. However, on-chip TMDC-based valleytronic devices face challenges in efficiently routing valley-polarized emissions with large degrees of valley polarization, high directionality, position-independent robustness, and long propagation distances for future applications in information processing and transmission. Coupling a plasmon–exciton hybrid waveguide with a chiral plasmonic nanoparticle is a promising approach to address these challenges. The integrated waveguide can enhance the degree of valley polarization and transduce chirality-dependent valley information into optical spin angular momentum information that can be detected over a long distance. The capabilities provided by the plasmon–exciton hybrid waveguide hold profound implications for the development of valley-based optoelectronics22, ultrafast valley-polarized transport23, and valley-based qubits for quantum computing24.

Herein, we report on the assembly of chiral Au nanocubes (NCs) onto the surface of Ag nanowires (NWs) to achieve the routing of SPPs and PL in WS2 monolayers. The photonic spin-Hall effect is demonstrated with the (chiral Au NC)–NW hybrid waveguides under excitation of CPL. When the system is excited with linearly polarized laser light, the SPPs propagate preferentially in a specific direction along the NW, dictated by the chiroptical response of the attached chiral Au NC. The (chiral Au NC)–NW structures are further used to control the valley-polarized exciton emissions in WS2 monolayers and enhance the degree of circular polarization (DCP) under excitation of linearly polarized light. The pumping and decay rates of excitons located in the elliptically polarized electric field generated by the (chiral Au NC)–NW structures are calculated to investigate the preferential excitation and emission of excitons in one of the valleys. The polarization states of the localized electromagnetic field and the valley states of excitons can be readout by the photonic path of the NW based on the photonic spin-Hall effect. The ability to manipulate the coupling of light and excitons in a chirality-dependent manner using chiral plasmonic nanoparticles provides promising avenues for exploiting spin or valley degrees of freedom to achieve chiral sensors and valleytronic logic gates.

Results
Surface plasmon propagation excited by CPL and linearly polarized light

The (chiral Au NC)–NW hybrid waveguides were fabricated by assembling chiral Au NCs with distinct chiral morphologies on as-prepared Ag NWs that were deposited on Si/SiO2 substrates (Supplementary Figs. 1 and 2). D- and L-handed Au NCs were synthesized through seed-mediated overgrowth on Au nano-octahedra in the presence of chiral molecules, which directed asymmetric growth on high-Miller-index facets. The Ag NW with a single attached chiral Au NC can be found on the Si/SiO2 substrate (Fig. 1a, b). The coupled SPPs were launched as evidenced by the light spot at each end of the NW when a laser beam was focused on the attached chiral Au NC. The left and right outputs are designated by LO and RO, which correspond to the −x direction and +x direction, respectively. The (chiral Au NC)–NW devices with the chiral Au NC located roughly at the center of the Ag NW were fabricated and considered ideal chiral waveguides. These ideal waveguides can eliminate deviations in the LO and RO intensities induced by the different distances from the central position to the LO and RO positions because the output intensity of SPPs decays as the propagating distance along the Ag NW is increased. The intensity difference between the LO and RO in the ideal waveguide can thus be utilized to analyze the coupling efficiency of light propagating along the −x and +x directions. A coordinate system is defined for the fabricated (chiral Au NC)–NW structures. The x-axis is defined to be aligned along the longitudinal direction of the Ag NW. The chiral Au NC is defined to be always positioned on the +y side of the NW.

The chiral Au NC in a (chiral Au NC)–(Ag NW) structure was illuminated by a LCP or RCP laser beam at the wavelength of 633 nm (Fig. 1c). The scattered laser light at the junction of the hybrid structure induced strong light–matter interaction at the surface of the Ag NW, which leads to the excitation of SPP modes within the Ag NW. The LCP excitation led to main SPP emissions at the RO of the (D-handed chiral Au NC)–NW structures, whereas the RCP excitation led to main SPP emissions at the LO, as shown in the pseudocolor images in Fig. 1c (central column). Such a relationship between the propagating direction and the polarization of the incident light is called spin-direction locking or photonic spin-Hall effect. The (L-handed chiral Au NC)–NW structures under the CPL excitation exhibited a similar photonic spin-Hall effect, as evidenced by the pseudocolor images in Fig. 1c (right column). SPPs propagated to one end of the NW preferentially when the CPL was focused on the chiral Au NC.

The scattering g-factors of the individual chiral Au NCs supported on SiO2 substrates characterize the chiroptical responses of the chiral Au NCs25. The D- and L-handed chiral Au NCs scatter LCP and RCP light preferentially at the wavelength of 633 nm, respectively. A linearly polarized light can be decomposed into an equal amount of the LCP and RCP components. When the chiral Au NC of the (chiral Au NC)–NW structure is excited by 633 nm linearly polarized laser light, it can scatter light of a specific handedness preferentially. The SPP propagation of the (D/L-handed chiral Au NC)–NW structures under the excitation of 633 nm linearly polarized laser light was demonstrated (Fig. 1d). The incident laser light propagated along the −z direction, with its polarization along the y-axis. The results show that a D-handed chiral Au NC gives a larger SPP intensity at the RO, while the L-handed chiral Au NC gives a larger SPP intensity at the LO. The scanning electron microscopy (SEM) images of the (chiral Au NC)–NW structures with a D-handed chiral Au NC and an L-handed chiral Au NC, respectively, are shown in Supplementary Fig. 3.

The directionality of SPP propagation in the hybrid structure is defined as (IR − IL)/(IR + IL), where IR and IL are the intensities measured at the RO and LO, respectively. The normalized intensities of the LO and RO collected from three representative (D-/L-handed chiral Au NC)–NW devices excited separately by LCP and RCP laser light are summarized in Fig. 1e. The selected regions of the LO and RO in the charge-coupled device (CCD) images and the calculation of the LO and RO intensities are shown in Supplementary Fig. 4. The statistical directionality of the (D-/L-handed chiral Au NC)–NW shows good routing behaviors with a maximal directionality of ~1.0 under the excitation of LCP light, whereas a minimal directionality of about −1.0 was obtained under the excitation of RCP light. The spin-direction locking phenomenon under CPL is repeatable. These findings suggest that the chiroptical effect of the attached chiral nanoparticles is overshadowed by the handedness of the incident CPL. The coupling between the chiral Au NC and the Ag NW enhances the electric field at their junction while maintaining the polarization of the incident light. The LCP and RCP components of light in the gap region between the chiral Au NC and the Ag NW are coupled into the SPP modes with different propagation directions according to the photonic spin-Hall effect. The photonic spin-Hall effect was not violated when the chiral Au NC and the laser spot were moved away from the central position of the Ag NW and the attached chiral Au NCs were subjected to spatial rotations relative to the ideal chiral waveguide (Supplementary Fig. 5). More (chiral Au NC)–(Ag NW) structures were further fabricated and excited with linearly polarized laser light to evaluate the routing performance (Fig. 1f, g). The output intensities and directionality of the structures were calculated in the way described above. The chirality-dependent directional propagation of light can be reproduced. The RO intensities are higher than the LO intensities in all D-handed devices, while the LO intensities exceed the RO ones in all L-handed devices. The statistical results show that the directionality of SPP propagation fluctuates with the morphologies of the attached chiral Au NCs. A minimal directionality of about −0.96 for the L-handed devices and a maximal directionality of ~0.4 for the D-handed devices were obtained under the excitation of linearly polarized light.

The L-handed chiral Au NC of the hybrid structure was then excited by 633 nm linearly polarized laser light with polarization aligned parallel to the long axis of the Ag NW (Supplementary Fig. 6a). The intensity of the LO was higher than that of the RO. Rotating the polarization direction of the linearly polarized laser light by 90° still permitted the observation of the chirality-dependent directional propagation in the (chiral Au NC)–NW structure. Waveguides with chiral elements can be oriented in different directions relative to the linear polarization direction of incident light to achieve routing, whereas waveguides with achiral elements require a specific orientation or position relative to the direction of incident CPL for routing. In addition, only the light spot from the LO could be detected when the attached L-handed chiral Au NC was spatially rotated with respect to the ideal devices (Supplementary Fig. 6b, c), which indicates the maintenance of the chirality-dependent directional propagation in the structure. To further make a comparison with the results from the chiral structures, the SPP propagation in achiral structures was investigated (Fig. 1f, g and Supplementary Figs. 7–9). An achiral Au NC was assembled on the surface of the Ag NW. LCP and RCP exciting light were directionally coupled to the LO and RO of the NW, respectively, which is referred to as a reversed photonic spin‑Hall effect. Such a reversal highlights the role of plasmon coupling in spin-dependent routing. Under the excitation of linearly polarized light, the intensity difference between the LO and RO was negligible. The directional SPP propagation observed in the (chiral Au NC)–NW structures under linearly polarized light, therefore, originates from their chiroptical responses and the photonic spin‑Hall effect.

Theoretical demonstration of the photonic spin-Hall effect

The distributions of the electric field in the NW of the (chiral Au NC)–(Ag NW) structure under the excitation of 633 nm circularly polarized and linearly polarized dipoles were simulated by the finite-difference time-domain (FDTD) method (Fig. 2a). The propagating SPPs excited toward the +x direction appear to be stronger than those toward the −x direction under the illumination of LCP light. On the other hand, SPPs are more likely to propagate toward the −x direction under illumination of RCP light. The simulations for the (D-handed chiral Au NC)–(Ag NW) structure gave similar results (Supplementary Fig. 10), indicating that the photonic spin-Hall effect does not change with the chirality of the attached chiral Au NC. In contrast, the propagating direction of SPPs excited by linearly polarized dipoles is reversed when the attached chiral nanoparticle changes from L-handed to D-handed (Fig. 2a). The propagating SPPs preferentially propagate to the −x direction and the +x direction for an L-handed and D-handed chiral Au NC, respectively. The cross-sections of the Ag NWs were experimentally characterized as a smoothed pentagon (Supplementary Fig. 11a). The FDTD simulations of the (chiral Au NC)–(faceted pentagonal Ag NW) structures suggest that the spin-direction locking effect and the directional SPP propagations induced by the chirality of the attached chiral nanoparticle remain robust (Supplementary Fig. 11b–d). The simulations of the achiral hybrid structures demonstrated that the direction of SPP propagation under the excitation of CPL can be tuned by the plasmon coupling of the NW with different attached nanoparticles (Supplementary Fig. 12).

The photonic spin-Hall effect was theoretically demonstrated by calculating the intensities scattered into the plasmon modes of the Ag NW. The overlapping intensities for the incident LCP and RCP light can be determined by SLCP = |σLCP*·E|2 and SRCP = |σRCP*·E|2, respectively5, with σLCP and σRCP representing the polarization states of CPL. The theoretical calculation process of the fundamental modes26,27 and overlapping intensities of an infinitely long Ag NW are shown in Supplementary Figs. 13 and 14 and Supplementary Note 1. The propagating plasmon modes of an Ag NW with a specific length and the overlapping intensities were reproduced by COMSOL and FDTD simulations. The hybrid modes, HE1 and HE−1 mode, of the Ag NW can be excited by linearly polarized light with y-direction and z-direction polarizations (Supplementary Fig. 15). The superscripts +x and −x of the HE modes represent the propagation direction of the SPP modes. The calculated overlaps localized on the surface of the NW show that the photonic spin-Hall effect is valid for the coupling between CPL illumination and the HE modes (Fig. 2b and Supplementary Figs. 16 and 17). The incident light from the HE modes (Fig. 2b and Supplementary Fig. 17) with LCP and −z (or −y) propagating direction is localized at the +y (or −z) side of the NW surface, and thus the SPP will be efficiently coupled by the HE+x mode, and the SPPs will propagate along the +x direction. The +x direction means that the SPPs will be routed to the RO of the Ag NW. When the incident electromagnetic field with RCP and −z propagation direction is localized at the +y side of the NW surface, the incident field efficiently couples into the HE−x mode and the excited SPPs propagate along the −x direction, corresponding to the LO of the NW. Such a mirror symmetry of SLCP and SRCP is also valid for the distributions of the overlapping intensities for CPL propagating along the −y or −z directions and the HE−1 mode (Supplementary Fig. 17). The mirror symmetry of SLCP and SRCP for the HE modes was reproduced by FDTD simulations and the calculations on the overlapping intensities (Supplementary Fig. 18 and Supplementary Note 2). The coupling efficiency of the plasmon modes in the NW and CPL is therefore determined by the polarization and the distribution of the localized electromagnetic field enhancement on the surface of the NW. The coupling of the nanoparticle and the NW modifies the directions of the Poynting vectors in the gap between the nanoparticle and the NW. Further analysis of the z‑component of the Poynting vector (Pz) in Supplementary Fig. 19 reveal that the sign reversal of Pz from negative to positive accounts for the transition from the normal to the reversed spin‑Hall effect. The theoretically demonstrated photonic spin-Hall effect can be used to explain the directionality of the SPP outputs when a chiral Au NC is positioned on the +y side of the NW surface and illuminated with a focused laser beam.

We also analyzed the photonic spin-Hall effect of the Ag NW coupling with elliptically polarized light by calculating the overlapping intensities. An elliptically polarized light propagating along the −z direction can be written as σ = (−e−iεe)/√2. The polarization ellipticity ε can take values between −1 (RCP) and +1 (LCP). The polarization of light becomes linear when ε is equal to 0. Sσ is defined as |σ*·E(y,z)|2. The Sσ/|E0|2 values between linearly polarized light and the HE1 mode are distributed separately and accumulated on the two sides of the NW, resulting in the malfunction of the photonic spin-Hall effect under the excitation of linearly polarized light (Supplementary Fig. 20). The overlaps between the HE−x mode and elliptically polarized light on the +y side of the NW surface decreases as ε is increased from −1 (RCP) to 0 (Fig. 2c). The overlaps between the HE+x mode and elliptically polarized light on the same side of the NW decreases as ε is decreased from +1 (LCP) to 0. The variation of Sσ/|E0|2 on the +y side of the NW surface for the HE−1 −x and HE−1 +x mode, respectively, as a function of ε shows similar results (Fig. 2c). The photonic spin-Hall effect under the excitation of elliptically polarized light only occurs when its ellipticity has a relatively large absolute value. The preferred propagation direction of SPPs in the hybrid structure can therefore be predicted by analyzing the distribution of the ellipticity at the junction and the photonic spin-Hall effect. The distributions of the ellipticity of the (chiral Au NC)–(Ag NW) structures were calculated to analyze the chirality-dependent SPP propagation. A 633 nm linearly polarized Gaussian beam with polarization perpendicular to the long axis of the Ag NW was illuminated on the chiral Au NC (Fig. 2d–g and Supplementary Figs. 21 and 22). The electric field is enhanced in the gap region between the chiral Au NC and the Ag NW. The coupling effect results in a strongly scattered electromagnetic field that can be efficiently coupled into the SPP modes of the Ag NW. The correlation between the ellipticity of light in the gap region, with the wave vector pointing toward the −z direction, and the routing effect was understood based on the calculation results. The distribution of the z-component of the Poynting vector Pz in the x–y plane ROI is shown in Supplementary Fig. 21c. The ellipticity angle η of the electric field in the x–y plane can be defined as tanη = tan(arcsin(S3/S0))/2, with the use of the Stokes parameters of S0 = |Ex|2 + |Ey|2 and S3 = 2Im(Ex*Ey). The distribution of tanη shows that the electromagnetic field in the gap region between the chiral Au NC and the Ag NW is elliptically polarized (Supplementary Fig. 21d). The strength of the ellipticity R in the gap region defined as −(tanη)Pz was used to analyze the routing effect of the (chiral Au NC)−(Ag NW) structures (Fig. 2d). The negative sign defines the direction of Pz to be pointing in the −z direction, which corresponds to the previously defined incident light direction. The sum of R in the line has a negative value of −5.8 × 10−10 for the (L-handed chiral Au NC)–NW structure, which indicates that the RCP component is dominant (Fig. 2e). The resultant right-handed elliptically polarized electromagnetic field in the gap region leads to a higher LO intensity, in accordance with the observed chirality-dependent directional propagation.

The distributions of Pz, tanη, and R in the x–y plane monitor were also calculated for the (D-handed chiral Au NC)–(Ag NW) structure using the same method as for the L-handed one (Fig. 2f and Supplementary Fig. 22). The sum of R in the line has a positive value of 7.8 × 10−10 for the (D-handed chiral Au NC)–NW structure, which indicates that the LCP component is dominant (Fig. 2g). The resultant left-handed elliptically polarized electromagnetic field in the gap region leads to a higher RO intensity. The handedness of the elliptically polarized electromagnetic field in the gap region induced by the D-handed chiral Au NC and L-handed chiral Au NC is opposite. The opposite handednesses originate from their different twisting directions of the chiral arms and concave surfaces. The SPPs in the NW can therefore be routed under the excitation of linearly polarized light depending on the chiroptical properties of the attached chiral nanoparticle. To investigate the effect of the distance between the chiral Au NC and the Ag NW on the SPP propagation, the chiral Au NCs were coated with a 15-nm-thick SiO2 shell (Supplementary Fig. 23). The SiO2 shell modulated the plasmon coupling and thus reversed the directionality compared to the results of the (chiral Au NC)–NW structures. The simulation results reveal that tuning the SiO2 thickness from 10 nm to 5 nm can switch the SPP propagation direction under linearly polarized excitation (Supplementary Fig. 24). The SPP routing depends not only on the chiroptical property of the nanoparticle but also on its plasmon coupling with the NW.

Chirality-dependent routing of the valley excitons in WS2 monolayers

The coupling of plasmons and valley excitons was investigated using the (chiral Au NC)–(Ag NW) structures combined with WS2 monolayers. The WS2 monolayers were grown by physical vapor deposition28. The (chiral Au NC)–(Ag NW)-on-WS2 structures were fabricated through a transfer process (Fig. 3a, b and Supplementary Fig. 25). The details of the fabrication process of the (chiral Au NC)–(Ag NW)-on-WS2 structures are provided in Methods. The (chiral Au NC)–(Ag NW) structures were utilized to alter the excitation and emission of nearby excitons in the WS2 monolayer (Fig. 3c). The localized surface plasmon resonance effect induced by the chiral Au NC resulted in an increase in the PL intensity of the WS2 monolayer when a laser beam was focused onto the chiral Au NC. The valley-polarized excitons in the WS2 monolayer can be considered as circular transition dipoles to couple with the SPP modes of the Ag NW29,30. The SPPs will propagate along the Ag NW and emit light at the ends. The experimental setup for the measurements of the PL spectra, as well as the LCP and RCP components of the PL emissions, is illustrated in Supplementary Fig. 26a. The PL spectra at the LO and RO of the Ag NW were measured simultaneously under the excitation of linearly polarized laser light propagating along the −z direction (Fig. 3d).

The correlation between the directionality of the SPP emissions and the chiroptical response of the chiral nanoparticle was investigated by examining the routing performance under the excitation of linearly polarized laser light at the wavelengths of 594 nm and 514 nm. The polarization direction of the excitation light for the PL emission measurements was aligned along the x-axis. The PL spectra at the outputs of the (chiral Au NC)–(Ag NW)-on-WS2 structure under the excitation of linearly polarized laser light were measured (Fig. 4a–d). The PL intensity of the RO at the peak wavelength (PLRO) is stronger than that of the LO (PLLO) under the excitation of 594 nm light (Fig. 4a) for the D-handed structure. The PL spectra of the L-handed structure under the excitation of 514 nm light show that PLLO is higher than PLRO (Fig. 4d). The directionality of the SPP emissions can be expressed by (PLRO − PLLO)/(PLRO + PLLO). The PL emission directionality is positive for the D-handed structure, whereas the routing direction is reversed with the L-handed structure (Fig. 4e). The PL spectra were also measured from NW-on-WS2 structures (Supplementary Fig. 26b). The dashed lines in Fig. 4a show that PLLO and PLRO for the NW-on-WS2 structure have nearly the same intensity, resulting in a near-zero directionality.

The scattering spectra of the attached chiral Au NCs in the (chiral Au NC)–(Ag NW)-on-WS2 structures were measured under illumination of CPL (Supplementary Fig. 27). The corresponding scattering g-factor spectra were utilized to explore the chiroptical responses of the chiral Au NCs at different excitation wavelengths. The scattering intensity of the attached D-handed chiral Au NC under LCP light is greater than that under RCP light, resulting in a positive scattering g-factor. In contrast, the scattering g-factor of the attached L-handed chiral Au NC is negative. The sign and magnitude of the scattering g‑factor reflect the handedness and strength of the chiroptical response, which governs the spin‑selective coupling of linearly polarized incident light into SPPs. A larger positive g‑factor at a given wavelength indicates stronger preferential scattering of LCP light, which lead to more pronounced directional propagation of SPPs toward the RO of the NW. A negative scattering g‑factor implies dominant RCP scattering and directional outputs toward the LO. The directionalities under the excitation of 594 nm and 514 nm laser light in Fig. 4e (D594 and D514, in short) and the scattering g-factors at the excitation wavelengths of 594 nm and 514 nm (g594 and g514, in short) are represented in Fig. 4f. The variations in D594 and D514 are correlated with the g594 and g514 values of the attached chiral Au NCs, respectively. The correlation stems from the chiral plasmonic resonance. The scattering g‑factor peak at the wavelength of 593 nm indicates strong chiroptical on‑resonance with 594 nm excitation. The 594 nm linear polarization excitation therefore efficiently enables a spin‑selective coupling into directional SPPs, yielding a high D594. In contrast, the much smaller g‑factor at 514 nm (g514) reflects off‑resonant chiroptical interaction. This results in a less efficient linear‑to‑elliptical polarization conversion and a trivial directionality (D514). The higher |g514| value than the |g594| value for the L-handed chiral Au NC results in higher |D514| than |D594| (Fig. 4f). The variation of the directionality of the SPP emissions is therefore dependent on the chiroptical response of the attached chiral Au NC.

The LCP- and RCP-resolved PL spectra and DCPs of the PL outputs were further investigated under the excitation of 594 nm and 514 nm linearly polarized laser light (Fig. 5 and Supplementary Fig. 28). The DCP of the PL can be expressed by (PLLCP − PLRCP)/(PLLCP + PLRCP), with PLLCP and PLRCP representing the LCP and RCP components of the PL at the peak wavelength, respectively. For the (Ag NW)-on-WS2 structure, PLRCP at the LO is stronger than PLLCP (Fig. 5a). PLLCP at the RO is stronger than PLRCP. The DCP of the PL at the LO is negative, while the DCP of the PL at the RO is positive (Fig. 5b). The DCPs of the LO for both L-handed and D-handed structures are positive, while the DCPs of the RO are negative (Fig. 5d, f). The absolute DCP values of the ROs are higher than those of the LOs for both the L-handed and D-handed structures. To further clarify the essential role of chiral plasmonic nanoparticles, we conducted a series of control experiments using a bare (Ag NW)-on‑WS2 structure without any attached nanoparticle and (achiral Au NC)–NW‑on‑WS2 structures (Supplementary Figs. 29–31). In all control cases, whether no particle, a single achiral Au NC, or an achiral Au NC dimer was attached, the PL intensities from the LO and RO showed negligible differences under linear polarization excitation, and the DCP remained close to zero. These results confirm that the chiral Au nanoparticle is essential for achieving the observed directional routing of PL. In contrast, achiral hybrids or the NW alone do not support directional output under the same excitation geometry.

Understanding of the chirality-dependent routing of valley-polarized emissions

Once valley excitons in the hybrid structures are pumped and excited, they can recombine through direct radiation, SPP excitation, and nonradiative damping, including intrinsic nonradiative decay and metal-induced nonradiative decay. The modulated DCP of valley-polarized emissions depends on the modulated pumping rate and the decay rate of excitons in the +K and −K valleys. The modulated pumping rate PLCP of excitons in the +K valley and PRCP of excitons in the −K valley are related to the modulus of the LCP and RCP components of the electric field (|ELCP|2 and |ERCP|2), respectively18. ELCP and ERCP can be calculated using ELCP = 1/√2(Ex − iEy) and ERCP = 1/√2(Ex + iEy).

The distributions of the electric field on the WS2 monolayer were calculated by FDTD. Gaussian beams with the different wavelengths of 594 and 514 nm were, respectively, illuminated at the center of the chiral Au NC along the −z direction. An x–y plane monitor, spanning an area of 700 nm × 80 nm, was placed on the surface of the WS2 monolayer. The center of this monitor was aligned with the center of the NW in the z direction. The monitor was equally divided into two ROIs, ROI 1 and ROI 2 (Fig. 6a). The excited SPPs by LCP excitonic emissions in ROI 1 will propagate to the RO, while those excited by RCP excitonic emissions in ROI 1 will route to the LO. The propagation directions of LCP and RCP excitonic emissions in ROI 2 interchange with each other based on the photonic spin-Hall effect. Figure 6a–g and Supplementary Fig. 32 show the simulated results for the (Ag NW)-on-WS2, (D-handed chiral Au NC)–(Ag NW)-on-WS2, and (L-handed chiral Au NC)–(Ag NW)-on-WS2 structures under the excitation of the 594 nm Gaussian beam. For an (Ag NW)-on-WS2 structure without any chiral Au NC, P in ROI 1 is comparable to P in ROI 1 (Supplementary Fig. 32b). In contrast, P in ROI 1 is larger than P in ROI 1 for the L-handed structure (Fig. 6b), while P in ROI 1 is larger than P in ROI 1 for the D-handed structure (Supplementary Fig. 32d). The modulated decay rates of the left-handed and right-handed circular dipoles (ΓLCP and ΓRCP) were simulated, respectively. The circular dipoles were placed below the (chiral Au NC)–(Ag NW) structure in the ROIs. ΓLCP and ΓRCP were normalized by the decay rate in the absence of any structure to estimate metal-induced nonradiative damping. The modulated pumping rates and decay rates were then multiplied. The obtained PLCPΓLCP and PRCPΓRCP were used to estimate LCP and RCP excitonic emissions, respectively (Fig. 6b and Supplementary Fig. 32b, d).

To compare the PΓ differences between the D-handed and L-handed structures more clearly, the distribution of PΓ along the x-axis within the ROIs 1 and 2 is presented in Fig. 6c–g. The results show that PRCPΓRCP in ROI 1 is larger than PLCPΓLCP in ROI 1 for the L-handed structure (Fig. 6c), while PRCPΓRCP in ROI 2 is larger than PLCPΓLCP in ROI 2 (Fig. 6d). The situation is reversed for the D-handed structure (Fig. 6e, f). The relative strength of each type of emission in the different ROIs and the contributions to the overall SPP emissions determine the emission intensities of the LO and RO based on the photonic spin-Hall effect. To discuss the contributions of the PΓ in the different ROIs to the overall output of the NW, (PΓ)j represents the summation of the PΓ over the region j, with j = 1 or 2, corresponding to ROI 1 or ROI 2. The results of (PLCPΓLCP)j and (PRCPΓRCP)j are presented in Fig. 6g. For both the D-handed and L-handed structures, (PRCPΓRCP)2 is larger than (PLCPΓLCP)2 for RO, while (PLCPΓLCP)1 is larger than (PRCPΓRCP)1 for LO. The obtained difference in the LCP and RCP components that contribute to the LO and RO is consistent with the measured results in Fig. 5c–f, showing a positive DCP for the LO and a negative DCP for the RO. The summation of (PLCPΓLCP)1 and (PRCPΓRCP)2 gives the contributions of the emissions coupled to RO and is designated as PΓRO. The summation of (PRCPΓRCP)1 and (PLCPΓLCP)2 contributes to LO and is designated as PΓLO. PΓLO is larger than PΓRO for the L-handed structure under the excitation of the 594 nm Gaussian beam, while PΓRO is larger than PΓLO for the D-handed structure (Fig. 6h, i). The calculated directionality is consistent with the measured results of the routing effect of the PL emissions in Fig. 4a–d. In contrast, PΓRO is comparable to PΓLO for the (Ag NW)-on-WS2 structure (Supplementary Fig. 32b). To compare the directionalities of the structures under different excitation wavelengths, the PΓRO and PΓLO of the D-handed and L-handed structures under the excitation of the 514 nm Gaussian beam are also shown in Fig. 6h. The diminishing difference between PΓLO and PΓRO under 514 nm excitation, compared to the results obtained with 594 nm excitation, is attributed to the weaker chiroptical response. The routing effect of the PL emissions in the (chiral Au NC)–(Ag NW)-on-WS2 structures under the excitation of linearly polarized light is, therefore, originated from chirality-dependent coupling between valley excitons and the modulated chiral electromagnetic field.

As an extended demonstration of chirality‑dependent routing, we embedded fluorophore molecules R640 in the SiO2 shell surrounding the chiral Au NC and studied the PL SPP routing of R640 molecules (Supplementary Figs. 33 and 34). Under linearly polarized excitation, the R640 emissions exhibit directional SPP propagation that reverses with the handedness of the attached chiral NC. The D‑handed structures route the fluorescence preferentially toward the LO, whereas the L‑handed structures route it toward the RO. Under LCP/RCP excitation, the D‑handed structures exhibit a more pronounced difference between the LO and RO under LCP than under RCP illumination, while the L‑handed structures show a greater output asymmetry under RCP than under LCP illumination. These results confirm that the chiral plasmon–emitter coupling imposes a spin‑selective directionality not only on excitonic emissions but also on molecular fluorescence emissions, underscoring the generality of chirality‑dependent routing.

Methods
Synthesizing the chiral Au NCs

The chiral Au NCs were synthesized using a two-step wet-chemistry method. Au nano-octahedrons with an edge size of ~30 nm were first grown by a seed-mediated method31. A freshly prepared, ice-cold sodium borohydride solution (NaBH4, 0.02 M, 0.45 mL) was mixed with an aqueous solution composed of gold chloride trihydrate (HAuCl4, 0.01 M, 0.25 mL), cetyltrimethylammonium chloride (CTAC, 0.2 M, 5 mL), and water (4.75 mL) under vigorous stirring. The resultant seed solution was kept at 35 °C for 1 h. Two solutions were prepared for the growth of the Au nano-octahedra. The solutions 1 and 2 were made by mixing CTAC (0.2 M, 20 mL), HAuCl4 (0.01 M, 1 mL), KI (0.001 M, 0.2 mL), ascorbic acid (AA, 0.04 M, 0.88 mL), and water (17.92 mL) sequentially. The formation of the Au nano-octahedrons was initiated by adding the seed solution (0.22 mL) to the growth solution 1, which was followed by gentle shaking for 5 s. The resultant solution (0.22 mL) was then added to the growth solution 2. The obtained mixture solution 2 was mixed by gentle shaking and then left undisturbed at room temperature for 45 min and then centrifuged at 1101 × g with a rotor radius of ~10.94 cm for 10 min. These nano-octahedrons (0.188 mL) were then used as the seeds for the growth of chiral Au NCs in an aqueous solution containing cetyltrimethylammonium bromide (CTAB, 0.1 M, 1 mL), AA (0.2 M, 0.25 mL), HAuCl4 (0.01 M, 0.3 mL), and glutathione (GSH, 2.75 mM, 0.12 mL). The mixture solution turned red after 3 h of storage at 35 °C. The GSH molecules tethered to the Au surface controlled the chirality of the high-Miller-index facets, resulting in chiral Au NCs with four highly curved arms on each facet. The average edge size of the chiral Au NCs is ~150 nm.

Synthesizing the Ag NWs

The Ag NWs were synthesized through the overgrowth of Ag on Au nanobipyramid (NBP) seeds32,33. A freshly prepared and ice-cold NaBH4 (0.01 M, 0.15 mL) was rapidly mixed with an aqueous mixture containing HAuCl4 (0.01 M, 0.125 mL), trisodium citrate (0.01 M, 0.25 mL), and water (9.625 mL) under vigorous stirring. The resultant seed solution was kept at room temperature for 2 h. Subsequently, 0.8 mL of the as-prepared seed solution was introduced into a pre-mixed growth solution consisting of CTAB (0.1 M, 40 mL), HAuCl4 (0.01 M, 2 mL), silver nitrate (AgNO3, 0.02 M, 0.2 mL), HCl (1 M, 0.8 mL), and AA (0.2 M, 0.16 mL). After being stirred for 2 min, the mixture was left undisturbed overnight at 35 °C. The Au NBPs were centrifuged at 5992 × g with a rotor radius of ~10.94 cm for 10 min and redispersed in 10 mM CTAB solution for subsequent use. The diameter of the Ag NWs was determined by the waist diameter of the Au NBPs. For the NBP samples used in our experiments, the extinction value per 0.5 cm at the longitudinal plasmon peak of 800 nm was 1.7. The Au NBP solution (40 mL) was centrifuged at 4403 × g with a rotor radius of ~10.94 cm for 8 min. The precipitate was redispersed in cetyltrimethylammonium chloride (CTAC, 0.08 M, 30 mL), followed by subsequent addition and mixing of AgNO3 (0.02 M, 4 mL) and AA (0.2 M, 2 mL). The mixture solution was placed in an air-bath shaker (60 °C, 180 rpm) and kept for 6 h. The resultant sample was centrifuged at 1957 × g with a rotor radius of ~10.94 cm for 10 min. The precipitate was redispersed in CTAB (0.03 M, 30 mL) overnight for sedimentation. The supernatant was composed of irregular Ag nanoparticle impurities, and the sediment was composed of pure Ag nanorods. The precipitate was redispersed in CTAC (0.08 M) for another overgrowth process to grow longer Ag nanorods. The volumes of the AgNO3 solution (0.02 M) and AA solution (0.2 M) in each overgrowth cycle for the Ag NW sample were 8 mL and 4 mL, respectively. The overgrowth process was repeated several times until the expected length was reached. The Ag NW precipitate was finally redispersed in CTAB (0.05 M, 30 mL) for long-term storage. The transmission electron microscopy (TEM) image of the synthesized Au NBP seeds and the SEM image of the Ag NWs with an average length of 8 μm are shown in Supplementary Fig. 1a, b, respectively.

Fabrication of the (chiral Au NC)–(Ag NW) and (chiral Au NC)–(Ag NW)-on-WS2 structures

The diluted Ag NW solution was initially deposited onto a Si/SiO2 substrate and left undisturbed for 10 s. The substrate was then blown dry with nitrogen gas. The chiral Au NCs were then deposited onto the same substrate and left undisturbed for 20 s followed by the same drying procedure. The chiral Au NCs were adhered to the surface of the Ag NWs. WS2 monolayers were grown on Si/SiO2 substrates at temperatures of 1170–1200 °C by physical vapor deposition28. The grown WS2 monolayers had high crystallinity and large areas of ~1 mm2. The (chiral Au NC)–(Ag NW)-on-WS2 structures were fabricated by a transfer process. The diluted Ag NW solution was initially deposited onto a polydimethylsiloxane (PDMS) substrate. The PDMS substrate was then baked on a hot plate at 35 °C for 2 min and blown dry with nitrogen gas. The chiral Au NCs were then deposited onto the same substrate and left undisturbed for 4 min. The substrate was blown dry again with nitrogen gas. The ideal (chiral Au NC)–(Ag NW) structures deposited on the PDMS substrate were transferred onto a piece of WS2 monolayer after close contact between the surface of the PDMS substrate and the WS2 monolayer at 50 °C for 20 min. The PDMS film was then peeled off from the Si/SiO2 substrate.

Single-particle optical measurements and characterization

Backward dark-field scattering measurements were carried out on a home-built optical microscope. An upright optical microscope (Olympus, BX53M) was integrated with a quartz-tungsten-halogen lamp (100 W) and a digital color camera (Olympus, DP73). A 100× dark-field air objective (Olympus, numerical aperture: 0.9) was used. The incident light from the halogen lamp passed through a dark-field objective to form an annular light beam. The annular light was focused on the sample at an oblique incident angle. The scattered light was collected by the same objective in the case of backward scattering and then directed toward a digital color camera. The dark-field scattering images of the chiral Au NCs and Ag NWs could thus be captured. The measurements of scattering spectra were conducted using the optical microscope equipped with a monochromator (Acton, SpectraPro 2360i) and a cooled CCD camera (Princeton Instruments, Pixis 400) maintained at a temperature of −70 °C. Circularly polarized excitation was realized by a linear polarizer and a quarter-wave plate (WPA4420-450-650, Union Optic) with a working spectral range of 450–650 nm. The polarization handedness convention used in this work was such that the RCP and LCP vectors rotate clockwise and counterclockwise along the propagation axis, respectively. The scattering g-factor is defined as g-factor = 2 × (SLCP − SRCP)/(SLCP + SRCP), with SLCP and SRCP corresponding to the scattering spectra under LCP and RCP light, respectively. Extinction spectra were measured on a PerkinElmer Lambda 950 ultraviolet/visible/near-infrared spectrophotometer. SEM imaging was carried out on an FEI QF400 field-emission scanning electron microscope operated at 20 kV. TEM imaging was carried out on an FEI TEM TS12 operated at 120 kV.

Surface plasmon polariton excitation and detection

The experimental setup for the measurements of the SPP outputs of the NW was based on a laser light source, a plasmonic waveguide, an optical microscope, and a digital color camera. A 633-nm laser beam was used as the excitation source. The incident laser light was focused on the chiral Au NC. The incident light was scattered at the asymmetrical positions on the surface of the NW, causing the momentum component of light to align with that of the SPPs. The illumination at the chiral Au NC, therefore, led to SPP outputs at the ends of the NW. The scattered light was collected with a 100× objective and then directed to the color camera. The image of the scattered light was taken to assist in visualizing the spatial distribution and intensity of the SPP outputs from the NW.

Preparation of the (chiral Au NC)@SiO2 nanoparticles

The (chiral Au NC)@SiO2 core@shell nanoparticles were synthesized by the growth of a mesostructured SiO2 shell onto the chiral Au NCs through the hydrolysis of tetraethyl orthosilicate (TEOS). The chiral Au NC sample was washed to remove extra CTAB and redispersed in water (1 mL). NaOH (0.1 M, 10 µL) and CTAB (0.1 M, 10 µL) solutions were then added. A SiO2 precursor was prepared by mixing TEOS (1 mL) with ethanol (9 mL). Under continuous stirring, the precursor solution (10 µL) was added dropwise to the chiral Au NC dispersion every 20 min. After the addition of the precursor solution in 1 h (a total of 30 µL of the precursor solution added), stirring was continued for 5 h to allow for the hydrolysis and formation of a mesostructured SiO2 shell. The obtained nanoparticle sample was finally washed twice and redispersed in ethanol.

Preparation of the (chiral Au NC)–fluorophore nanoparticles

The (chiral Au NC)–fluorophore nanoparticles were synthesized with a modified procedure to incorporate the R640 fluorophore into the mesostructured SiO2 shell. The process began identically, with the washing and redispersion of the chiral Au NCs and the addition of the same NaOH and CTAB solutions. The key difference was in the preparation of the precursor solution. R640 (50 mg) was first dissolved in ethanol (5 mL), and the resultant solution was then mixed with TEOS (1 mL) and ethanol (4 mL) to form a fluorophore-containing SiO2 precursor. The same protocol (3 µL every 20 min for 1 h) was then executed, which was followed by stirring for a total time of 5 h. The SiO2 shell formed on the surface of the chiral Au NCs with R640 molecules embedded. The final nanoparticles were washed twice and redispersed in water.

PL spectroscopy

The experimental setup for the measurements of PL spectra was based on a laser light source, a set of polarizers, a long-pass filter, an optical microscope, a monochromator, and a cooled CCD camera. Two lasers at the wavelengths of 514 nm and 594 nm were employed for PL excitation. A linear polarizer was inserted between the laser output port and the beam splitter for the control of the linear polarization direction of the laser light. A 593 nm long-pass filter (FF01-593/LP-25, AVR Optics) and a 550 nm long-pass filter (FELH0550, Thorlabs) were placed in front of the spectrometer to block the 594 nm and 514 nm excitation laser light, respectively. An additional set of optical polarizers, including a linear polarizer and a broadband quarter-wave plate, was inserted between the beam splitter and the long-pass filter for the detection of polarization-resolved PL spectra. PL and polarization-resolved PL spectra were measured by the monochromator and the cooled CCD camera.

Electrodynamic simulations

The electromagnetic simulations were performed using FDTD Solutions 2020 R2 (Lumerical) and COMSOL Multiphysics 6.3. During FDTD simulations, a (chiral Au NC)–(Ag NW) structure was placed on a substrate. A Gaussian beam was launched at the central position of the chiral Au NC along the −z direction. An etched cube model was used to emulate the morphology of the actual chiral Au NC as closely as possible. The Ag NW was modeled as a cylinder with a length of 8 µm. The gap distance between the chiral Au NC and the Ag NW was set at 2 nm. The WS2 monolayer with a thickness of 1 nm was modeled, with the thickness of the SiO2 substrate set at 740 nm to occupy the simulation region below the monolayer. In the simulations, a mesh size of 2 nm was used for the chiral Au NC, 1 nm for the WS2 monolayer, and 3 nm for the Ag NW. These mesh sizes were chosen to balance the computational accuracy and efficiency. The dielectric functions of Au and Ag were taken from Johnson and Christy’s data. The dielectric function of the WS2 monolayer with a thickness of 1 nm was calculated by fitting the experimental data in a previous work34. The refractive index of the SiO2 substrate was set at 1.45. CPL was produced when the two orthogonal electric field component vectors were of equal magnitude and out of phase by 90°. The phase of the x-polarized plane wave was fixed at 0°. A positive phase difference of +90° between the y- and x-polarized plane waves gave LCP light. A negative phase difference of −90° gave RCP light. For the simulations of decay rates, 633 nm circular dipole sources were placed below the (chiral Au NC)–(Ag NW) structure. During COMSOL simulations on the plasmon modes of the Ag NW and the overlapping intensities, a perfectly matched layer was applied as the boundary to absorb the outgoing radiation. The refractive index of the air was set at 1.00.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This work reports an assembly system of chiral Au NCs onto the surface of Ag NWs, and demonstrate the routing effect of\nSPPs modulated by the chirality of attached Au NCs under excitation of linearly polarized light. Furthermore, the Au NC-Ag\nNW assembly on WS2 monolayer induce directionally emissions of valley-polarized excitons and enhance the degree of\nvalley polarization. The underlying mechanism understanding is further explained through numerical simulations. The\noptical chirality and spin manipulation are intriguing physical properties and have drawn intense attention in many research\nfields. This work presents an interesting assembly structure and clear experimental results. I think it could be accepted for\npublication. While some concerns listed below should be addressed.\n1. In this work, the experimental results of left-handed and right-handed devices are compared with bare Ag NWs. Why not\nusing an assembly of achiral nanoparticle-NW hybrid? The coupling of nanoparticle of Ag NWs may lead some effects exist\nin chiral Au NC–NW hybrid, while not exist in bare Ag NWs.\n2. In Fig. 3f, the difference between RO and LO is very small. It may lead to a g-factor even smaller than that of the dashed\nlines in Fig. 3e of bare Ag NW. In the experiment, what reason would affect the chiral responses in the hybrid system?\n3. In Fig. 4, the DCP enhancement of left-handed and right-handed devices is evaluated based on the AgNW-on-WS2\nsample. How about the result if a sample of achiral AuNC-AgNW-on-WS2 was used? Does the coupling of nanoparticle and\nnanowire influence the chiral responses?\n4. The 594-nm and 514-nm excitations lead to different influence for the left-handed and right-handed devices. What is the\ndetailed reason?\n5. Could the distance between chiral Au NCs and Ag NWs be controlled in the experiment? This distance may influence the\nplasmon coupling and then the SPP excitation in the nanowires. Meanwhile, the space distance between plasmonic\nstructure and WS2 monolayer may affect the exciton PL and emission dynamics.", "reviewer_2": "Directional light splitting based on the photonic spin-Hall effect is demanding for the development of spin-dependent optical\nelements but still greatly missing. Here we report on the routing of surface plasmon polaritons (SPPs) by use of chiral Au\nnanocubes (NCs). Experiments and theoretical modeling have been performed to understand the photonic spin-Hall effect in\nan Ag nanowire (NW) under excitation of circularly polarized light. The SPPs in the Ag NW can be modulated by the\nattached chiral Au NCs with opposite chiralities under excitation of linearly polarized light. Hybrid structures are further\nconstructed out of (chiral Au NC)-(Ag NW) assemblies and transition metal dichalcogenide monolayers to selectively induce\ndirectional emissions of valley-polarized excitons and enhance the degree of valley polarization. The research group has\ngood experimental equipment and proficient operational skills. Many drawing details expressions are need modified.\n1. In the caption of Figure 1 (e), directly using CPL to describe the experimental design lacks guidance. It is suggested to\nmake the following two modifications:\n1) supplement the previous text to clarify that CPL has two chirality, namely LCP/RCP.\n2) clarify in the relevant discussion of Figure 1 (e) that the experiment was conducted separately by LCP and RCP\n2. Taking Figure 2 (b) as an example, it is recommended to use two different colors, red and blue, to distinguish between\nLCP and RCP light sources with different chirality。\n3. The article does not discuss the chirality of gold nanocubes. How is their chirality determined through SEM images? I\nsuggest the author can clearly indicate or supplement the synthesis pathway, or provide corresponding chiral optical effects\nthat can be distinguished. It is recommended that the author refer to the judgment methods of relevant research on the\nsynthesis of this particle for discussion and supplementation\n4. Supporting Figure S8(a) suggest placing the coordinate axis at the front to help readers read and understand.\n5. Will this quadrilateral structure have resonance problems like previous studies？in FigureS17\nref：L. Shan, F. Zhang,J. Ren et al. Large Purcell enhancement with nanoscale non-reciprocal photon. transmission in\nchiral gap-plasmon-emitter systems. Opt Express, 2020,28(23): 33890-33899\n6. The structure of WS2 and silver nanowires can also cause directional propagation when incident by CPL. Will linearly\npolarized light incident in the article also have a similar effect? I hope the author can further discuss this issue. If linearly\npolarized light directly irradiates the WS2 line structure without causing directional propagation, it directly proves the optical\neffect of gold nanostructures; If it will lead to directional propagation, the author needs to supplement the discussion on how\nto avoid the influence of silver nanowires on the experimental results when designing the experiment (such as removing\nonly gold nanoparticles to see if the propagation direction will be affected).\n7. Can we discuss the impact of geometric positions? How to control the relative position of gold and silver in the\nexperiment? If the experiment cannot be controlled, should we consider adding relevant simulations for theoretical\ncalculations?\n8. In this study, the optical properties of gold nanocubes were limited to the conversion of linearly polarized light. The article\nalso mentioned the enhancement effect of the structure's composition on electromagnetic fields. Can Raman and other\noptical properties be further studied?\n9 figure 1 D-hand and L-hand’s color bar have different value, why is the same value?"}, "author_response": "Response to Reviewer #1\nComments: This work reports an assembly system of chiral Au NCs onto the surface of Ag\nNWs, and demonstrate the routing effect of SPPs modulated by the chirality of attached Au\nNCs under excitation of linearly polarized light. Furthermore, the Au NC-Ag NW assembly on\nWS2 monolayer induce directionally emissions of valley-polarized excitons and enhance the\ndegree of valley polarization. The underlying mechanism understanding is further explained\nthrough numerical simulations. The optical chirality and spin manipulation are intriguing\nphysical properties and have drawn intense attention in many research fields. This work\npresents an interesting assembly structure and clear experimental results. I think it could be\naccepted for publication. While some concerns listed below should be addressed.\nResponse: We thank this reviewer for the effort made to evaluate our work, the positive\ncomments, and the valuable suggestions.\nQuestion 1: In this work, the experimental results of left-handed and right-handed devices are\ncompared with bare Ag NWs. Why not using an assembly of achiral nanoparticle-NW hybrid?\nThe coupling of nanoparticle of Ag NWs may lead some effects exist in chiral Au NC–NW\nhybrid, while not exist in bare Ag NWs.\nResponse: We thank the reviewer for this valuable suggestion. The reason for investigating\nthe chiral devices is to demonstrate the effect of chirality. We agree that comparing the results\nwith those of achiral hybrids is essential. The achiral hybrids can exhibit directional\npropagation only under circularly polarized light (CPL), whereas the chiral hybrids exhibit\nrobust directional propagation under linearly polarized light.\nWe have added new results of the surface plasmon polariton (SPP) propagation in a Ag\nnanowire (NW) with an attached Au nanocube (NC) under the excitation of left-handed and\nright-handed circularly polarized (LCP and RCP) laser light in Supplementary Fig. 7. The edge\nlength of the Au NC was ~130 nm. The 633 nm LCP and RCP laser light were directionally\ncoupled toward the left and right outputs (LO and RO) of the NW, respectively. The output\nintensities for 3 (Au NC)–NW structures showed similar results. We define the reversed\nspin‑Hall effect where under the excitation of light along the –z direction, LCP and RCP\nexciting light propagate toward the LO and RO, respectively. The propagation directions for\nLCP and RCP light in the achiral hybrids are opposite to those in the chiral hybrids. Such a\nreversal highlights the role of plasmon coupling in spin-dependent routing. The coupling of the\nPage 1 of 26\nnanoparticle and the NW can modify the direction of the localized energy flow in the gap region\nbetween the nanoparticle and the NW. The simulated results will be discussed later.\nSupplementary Fig. 7 | Reversed photonic spin-Hall effect in the (Au NC)–(Ag NW)\nstructures. a SEM images of a (Au NC)–(Ag NW) structure. The Au NC is located at the\ncentral position of the Ag NW. The edge length of the Au NC is ~130 nm. b Pseudocolor dark-\nfield microscopy image of the (Au NC)–NW structure (i) and pseudocolor images for the\nillumination of LCP (ii) and RCP (iii) laser light. The LCP and RCP laser light are directionally\ncoupled toward the LO (red box) and RO (yellow box) of the NW, respectively. c Normalized\nintensities of the LO and RO of the SPP propagation in the (Au NC)–NW structures under the\nexcitation of LCP and RCP light. The data were collected and averaged from 3 (Au NC)–NW\nstructures, respectively. Normal photonic spin‑Hall effect in Fig. 1c is defined as the scenario\nin which under the excitation of CPL along the –z direction, LCP‑ and RCP‑excited SPPs\npropagate toward the RO and LO of the NW, respectively. In contrast, the reversed spin‑Hall\neffect in (b) describes the flipped case where under the same incident CPL along the –z\ndirection, LCP‑ and RCP‑excited SPPs propagate toward the LO and RO, respectively.\nThe SPP propagation in the (Au NC)–(Ag NW) structures under the excitation of linearly\npolarized light has been added in Supplementary Fig. 8. Under linear polarization excitation,\nthe output intensity difference between the LO and RO of the NW was insignificant. The output\nintensities for 4 (Au NC)–NW structures showed similar results (Supplementary Fig. 8c).\nThese experiments confirm that the strong directional output observed in the (chiral Au NC)–\nNW structures under linearly polarized light arises from the combined effect of chiroptical\nresponses and the photonic spin‑Hall effect.\nPage 2 of 26\nSupplementary Fig. 8 | Surface plasmon propagation in the (Au NC)–(Ag NW) structures\nunder the excitation of linearly polarized light. a SEM images of a (Au NC)–(Ag NW)\nstructure. The Au NC is located at the central position of the Ag NW. b Pseudocolor dark-field\nmicroscopy image of the (Au NC)–NW structure (i) and pseudocolor image for the illumination\nof linearly polarized laser light (ii). The output intensity difference between the RO (yellow\nbox) and LO (red box) of the NW is insignificant. c Normalized intensities of the LO and RO\nof the SPP propagation in the (Au NC)–NW structures under the excitation of linearly polarized\nlaser light. The data were collected and averaged from 4 (Au NC)–NW structures.\nThe normalized intensity and the directionality of the SPP outputs for the (achiral Au NC)–\nNW structures under the excitation of linearly polarized light have been included in Fig. 1f, g.\nFig. 1 | Photonic spin-Hall effect in the (chiral Au NC)–NW structures. a, b Schematics\nand SEM images of …… f, g Normalized intensities of the LO and RO (f) and directionality\nof the SPP propagation (g) in the (D-/L-handed chiral Au NC)–NW structures and (achiral Au\nPage 3 of 26\nNC)–NW structures under the excitation of linearly polarized light. The data were collected\nfrom 4 (D-/L-handed chiral Au NC)–NW structures and 4 (achiral Au NC)–NW structures,\nrespectively.\nTo understand the reversed spin-Hall effect in achiral structures, the distributions of the electric\nfield enhancement for the (Au NC)–(Ag NW) structure under the excitation of polarized dipole\nsources were simulated (Supplementary Fig. 12a–c). LCP and RCP dipoles were respectively\nrouted along the –x and +x directions. Because the corners of Au NCs synthesized in\nexperiments are often rounded, we considered in the simulations Au NCs with their 6 corners\nrounded in different degrees. The sign of the directionality was found to remain unchanged,\nand the magnitude of the directionality increased when the attached nanoparticle was changed\nfrom a gold NC with sharp and right‑angle corners to NCs with rounded corners. Our\nsimulation results explained the reversed spin‑Hall effect observed in the (Au NC)–(Ag NW)\nstructures. Under linear polarization excitation, no directional propagation was observed for\nachiral structures (Supplementary Fig. 12a).\nSupplementary Fig. 12 | Simulations of the electric field of the (Au NC)–(Ag NW)\nstructures. a Distributions of the electric field enhancement in an x-y plane monitor located at\nthe bottom surface of the Ag NW in the (Au NC)–(Ag NW) structure under the excitation of\ncircularly and linearly polarized dipole sources. For circularly polarized dipoles, SPPs\npropagated along the –x direction for the LCP dipole, whereas SPPs propagated along the +x\ndirection for the RCP dipole. For linearly polarized dipoles, no directional propagation was\nobserved in the achiral structures. b, c Reversed photonic spin-Hall effect for the (Au NC with\nrounded corners)–(Ag NW) structures under the excitation of circularly polarized dipole\nsources. The corner-rounded Au NCs with fillet radii of 20 nm and 50 nm are denoted as R20\n(b) and R50 Au NC (c), respectively. The sign of the directionality remained unchanged\nrelative to (a), but the magnitude of the directionality increased as the corners of the attached\nPage 4 of 26\nNC became more rounded. d Normal spin-Hall effect in the (Au NC dimer)–(Ag NW) structure\nunder the excitation of circularly polarized dipole sources. LCP and RCP excitations were\ndirected toward the RO and LO of the NW, respectively. The position of the x-y plane monitor\nis identical in (a–d). The left panel schematically shows the cross‑sectional configurations of\nthe achiral Au NCs attached to the surface of the Ag NW.\nFor the (Au NC dimer)–(Ag NW) structure (Supplementary Fig. 12d), LCP and RCP dipoles\npropagated along the +x and –x directions, respectively. This reversal between the normal and\nreversed photonic spin-Hall effects can be attributed to a sign change in the z‑component of the\nPoynting vector (P ) induced by plasmon coupling between the nanoparticles and the NW. For\nz\nLCP light incident along the –z direction, the plasmonic interaction in the gap region can flip\nthe sign of P , as evidenced by its distribution along a line across the nanoparticle–NW gap\nz\n(Supplementary Fig. 19). P was negative (pointing in the –z direction) for structures with an\nz\nattached Au NC dimer or D‑/L‑handed chiral Au NC, whereas P was positive (pointing in the\nz\n+z direction) for those with R50 or R20 Au NCs. Since the opposite propagating direction of\nlight in the coupling fields gives rise to opposite SPP coupling direction, this sign reversal of\nP from negative to positive accounts for the transition from the normal to the reversed\nz\nspin‑Hall effect. This interpretation is consistent with the simulation results under the excitation\nof circularly polarized dipole sources in Supplementary Figs. 10, 12 and Fig. 2a.\nSupplementary Fig. 19 | Simulations of the z-component of the Poynting vector P under\nz\nLCP Gaussian beam. a Schematic of the (R50 Au NC)–(Ag NW) structure and the\ndistribution of P in an x-y plane monitor. The red dashed line represents the position of the\nz\nR50 Au NC. b–f Distributions of P in the line at the gap between the plasmonic nanoparticle\nz\nand the Ag NW as shown in the black dashed line of (a). The plasmonic nanoparticles are R50\nAu NC (b), R20 Au NC (c), Au NC dimer (d), D-handed chiral Au NC (e), and L-handed chiral\nAu NC (f), respectively. The directions of P in the (R50 Au NC)–NW and (R20 Au NC)–NW\nz\nstructures (b, c) are along the +z direction, which are opposite to those of the cases with the Au\nPage 5 of 26\nNC dimer and the chiral Au NCs (d–f).\nWe have added the experimental results of the normal photonic spin-Hall effect for a (Au NC\ndimer)–(Ag NW) structure under the excitation of LCP/RCP light in Supplementary Fig. 9.\nThe LCP and RCP laser light were directionally coupled toward the RO and LO of the NW,\nrespectively.\nSupplementary Fig. 9 | Photonic spin-Hall effect in a (Au NC dimer)–(Ag NW) structure.\na SEM images of a (Au NC dimer)–(Ag NW) structure. The Au NC dimer is located at the\ncentral position of the Ag NW. b Pseudocolor dark-field microscopy image of the (Au NC\ndimer)–NW structure (i) and pseudocolor images for the illumination of LCP (ii) and RCP (iii)\nlaser light. The LCP and RCP laser light were directionally coupled toward the RO (yellow\nbox) and LO (red box) of the NW, respectively.\nWe have added the discussion about the SPP propagation for achiral structures at the end of\nthe paragraph right before the section of “Theoretical demonstration of the photonic spin-Hall\neffect”.\n“…… In addition, only the light spot from the LO could be detected when the attached L-\nhanded chiral Au NC was spatially rotated with respect to the ideal devices (Supplementary\nFig. 6b, c), which indicates the maintenance of the chirality-dependent directional propagation\nin the structure. To further make comparison with the results from the chiral structures, the SPP\npropagation in achiral structures was investigated (Fig. 1f, g and Supplementary Figs. 7–9). An\nachiral Au NC was assembled onto the surface of the Ag NW. LCP and RCP exciting light\nwere directionally coupled to the LO and RO of the NW, respectively, which is referred to as\na reversed photonic spin‑Hall effect. Such a reversal highlights the role of plasmon coupling in\nspin-dependent routing. Under the excitation of linearly polarized light, the intensity difference\nbetween the LO and RO was negligible. The directional SPP propagation observed in the\n(chiral Au NC)–NW structures under linearly polarized light therefore originates from their\nchiroptical responses and the photonic spin‑Hall effect.”\nWe have added the discussion about Supplementary Fig. 12 at the end of the paragraph right\nbefore Fig. 2.\n“…… The FDTD simulations of the (chiral Au NC)–(faceted pentagonal Ag NW) structures\nsuggest that the spin-direction locking effect and the directional SPP propagations induced by\nthe chirality of the attached chiral nanoparticle remain robust (Supplementary Fig. 11b–d). The\nsimulations of the achiral hybrid structures demonstrated that the direction of SPP propagation\nPage 6 of 26\nunder the excitation of CPL can be tuned by the plasmon coupling of the NW with different\nattached nanoparticles (Supplementary Fig. 12).”\nWe have added the discussion about Supplementary Fig. 19 in the paragraph right after Fig. 2.\n“…… The coupling efficiency of the plasmon modes in the NW and CPL is therefore\ndetermined by the polarization and the distribution of the localized electromagnetic field\nenhancement on the surface of the NW. The coupling of the nanoparticle and the NW modifies\nthe directions of the Poynting vectors in the gap between the nanoparticle and the NW. Further\nanalysis of the z‑component of the Poynting vector (P ) in Supplementary Fig. 19 reveals that\nz\nthe sign reversal of P from negative to positive accounts for the transition from the normal to\nz\nthe reversed spin‑Hall effect. The theoretically demonstrated photonic spin-Hall effect can be\nused to explain ……”\nWe have also added discussion after the caption of Supplementary Fig. 19.\n“The reversal between the normal and reversed photonic spin-Hall effects can be attributed to\nthe sign change of P induced by the plasmon coupling between the nanoparticle and the NW.\nz\nFor LCP light incident along the –z direction, the plasmonic interaction in the gap region flips\nthe sign of P , as evidenced by its distribution along a line across the nanoparticle–NW gap\nz\n(Supplementary Fig. 19). P is negative (pointing in the –z direction) for structures with an\nz\nattached Au NC dimer or D‑/L‑handed chiral Au NC, whereas P is positive (pointing in the\nz\n+z direction) for those with the R50 or R20 Au NC. Since the opposite propagating directions\nof light in the coupling fields give rise to opposite SPP coupling directions, this sign reversal\nof P from negative to positive accounts for the transition from the normal to the reversed\nz\nspin‑Hall effect. This interpretation is consistent with the simulation results under the excitation\nof circularly polarized dipole sources in Supplementary Figs. 10, 12 and Fig. 2a.”\nQuestion 2: In Fig. 3f, the difference between RO and LO is very small. It may lead to a g-\nfactor even smaller than that of the dashed lines in Fig. 3e of bare Ag NW. In the experiment,\nwhat reason would affect the chiral responses in the hybrid system?\nResponse: We thank this reviewer for the valuable comment and question. The small\ndifference between the RO and LO in Fig. 3f is attributed to the weak chiroptical response of\nthe D-handed structure at 514 nm. This is corroborated by the scattering dissymmetry factor\n(g-factor) measurements of the chiral structures presented in Supplementary Fig. 27. The\nintensity of the scattering g-factor for the D-handed structure at 514 nm is significantly lower\nthan that at 594 nm.\nThe corresponding discussion has been expanded and presented more clearly in the second\nparagraph after Fig. 3.\n“…… In contrast, the scattering g-factor of the attached L-handed chiral Au NC is negative.\nThe sign and magnitude of the scattering g‑factor reflect the handedness and strength of the\nchiroptical response, which governs the spin‑selective coupling of linearly polarized incident\nlight into SPPs. A larger positive g‑factor at a given wavelength indicates stronger preferential\nscattering of LCP light, which leads to more pronounced directional propagation of SPPs\nPage 7 of 26\ntoward the RO of the NW. A negative scattering g‑factor implies dominant RCP scattering and\ndirectional outputs toward the LO. The directionalities under the excitation of 594 nm and 514\nnm laser light in ……”\nQuestion 3: In Fig. 4, the DCP enhancement of left-handed and right-handed devices is\nevaluated based on the AgNW-on-WS2 sample. How about the result if a sample of achiral\nAuNC-AgNW-on-WS2 was used? Does the coupling of nanoparticle and nanowire influence\nthe chiral responses?\nResponse: We thank the reviewer for raising this important point. We have performed the\nsuggested measurements using achiral structures. The results have been added in\nSupplementary Figs. 30, 31. When a single Au NC is coupled to the Ag NW on WS monolayer\n2\n(Supplementary Fig. 30), the photoluminescence (PL) intensities from the LO and RO show\nnegligible difference, and the polarization‑resolved PL spectra reveal minimal degrees of\ncircular polarization (DCPs) under either 594 nm or 514 nm excitation. Both directionality and\nDCP of the outputs under linear polarization excitation are markedly weaker than those\nobserved for the (chiral Au NC)–NW devices as shown in Figs. 3, 4. Even with the stronger\nelectric field enhancement induced by the (achiral Au NC dimer)–NW structure\n(Supplementary Fig. 31), no directional propagation emerges. These results confirm that the\ndirectional circular polarization emissions in the chiral structures originate from the chiroptical\nresponse of the attached chiral nanoparticle.\nPage 8 of 26\nSupplementary Fig. 30 | PL spectra and polarization-resolved PL spectra of the outputs\nof the (Au NC)–(Ag NW)-on-WS structure. a SEM images of a (Au NC)–(Ag NW)-on-WS\n2 2\nstructure. b PL spectra of the LO and RO under the excitation of 594 nm linearly polarized\nlaser light. c, d Polarization-resolved PL spectra of the LO (c) and RO (d) under the excitation\nof 594 nm linearly polarized laser light. e PL spectra of the LO and RO under the excitation of\n514 nm linearly polarized laser light. f, g Polarization-resolved PL spectra of the LO (c) and\nRO (d) under the excitation of 514 nm linearly polarized laser light.\nPage 9 of 26\nSupplementary Fig. 31 | PL spectra and polarization-resolved PL spectra of the outputs\nof the (Au NC dimer)–(Ag NW)-on-WS structure. a SEM images of a (Au NC dimer)–(Ag\n2\npolarized laser light. c, d Polarization-resolved PL spectra of the LO (c) and RO (d) under the\nexcitation of 594 nm linearly polarized laser light. e PL spectra of the LO and RO under the\nexcitation of 514 nm linearly polarized laser light. f, g Polarization-resolved PL spectra of the\nLO (c) and RO (d) under the excitation of 514 nm linearly polarized laser light.\nThe corresponding discussion has been added to the end of the paragraph right before Fig. 4.\n“…… The absolute DCP values of the ROs are higher than those of the LOs for both the L-\nhanded and D-handed structures. To further clarify the essential role of chiral plasmonic\nnanoparticles, we conducted a series of control experiments using a bare (Ag NW)-on‑WS\n2\nstructure without any attached nanoparticle and (achiral Au NC)–NW‑on‑WS structures\n2\n(Supplementary Figs. 29–31). In all control cases, whether no particle, a single achiral Au NC,\nor an achiral Au NC dimer was attached, the PL intensities from the LO and RO showed\nnegligible differences under linear polarization excitation, and the DCP remained close to zero.\nThese results confirm that the chiral Au nanoparticle is essential for achieving the observed\nPage 10 of 26\ndirectional routing of PL. In contrast, achiral hybrids or the NW alone do not support\ndirectional output under the same excitation geometry.”\nQuestion 4: The 594-nm and 514-nm excitations lead to different influence for the left-handed\nand right-handed devices. What is the detailed reason?\nResponse: We thank the reviewer for raising this insightful question. The distinct effects of\n594 and 514 nm excitation originate from the peak wavelength of the chiroptical resonances in\nthe hybrid structures. The scattering g‑factor of the D‑handed device indicates its chiroptical\nresponse, which shows the strongest g‑factor intensity at the wavelength of 593 nm\n(Supplementary Fig. 27). When the 594‑nm excitation is on resonance with this chiroptical\nresponse, the chiral structure generates a field with a higher degree of circular polarization and\nenables a directional SPP propagation observed in Fig. 3. In contrast, the 514‑nm excitation is\noff‑resonance, leading to a much weaker chiroptical response and consequently less effective\nlinear‑to‑elliptical polarization conversion. The diminished magnitude of ellipticity under the\nexcitation of 514 nm linearly polarized light results in a symmetric SPP propagation.\nThe corresponding discussion has been presented more clearly in the second paragraph after\nFig. 3.\n“…… The variations in D and D are correlated with the g and g values of the attached\n594 514 594 514\nchiral Au NCs, respectively. The correlation stems from the chiral plasmonic resonance. The\nscattering g‑factor peak at the wavelength of 593 nm indicates strong chiroptical on‑resonance\nwith 594 nm excitation. The 594 nm linear polarization excitation therefore efficiently enables\na spin‑selective coupling into directional SPPs, yielding a high D . In contrast, the much\n594\nsmaller g‑factor at 514 nm (g ) reflects off‑resonant chiroptical interaction. This results in a\n514\nless efficient linear‑to‑elliptical polarization conversion and a trivial directionality (D ). The\n514\nhigher |g | value than the |g | value for the L-handed chiral Au NC results in higher |D |\n514 594 514\nthan |D | (Fig. 3j)……”\nexperiment? This distance may influence the plasmon coupling and then the SPP excitation in\nthe nanowires. Meanwhile, the space distance between plasmonic structure and WS\n2\nmonolayer may affect the exciton PL and emission dynamics.\nResponse: We thank the reviewer for this excellent question. The response is divided into two\nparts.\n(1) Regarding the question about the distance between the chiral Au NC and the Ag NW, we\nhave added the SPP propagation results for (chiral Au NC)@SiO –NW structures in\nchiral Au NC with a 15-nm SiO shell (Supplementary Fig. 23). LCP and RCP were\n2\nrespectively routed toward the LO and RO of the NW. The normalized intensities were\ncollected and averaged from 3 (L-handed chiral Au NC)@SiO –NW structures under\ncoupled preferentially to the RO for the (L-handed chiral Au NC)@SiO –NW devices, while\nfor the D‑handed devices, they coupled to the LO (Supplementary Fig. 23b, d). The normalized\nintensities of the LO and RO and directionalities in the (L-/D-handed chiral Au NC)@SiO –\n23f, g. The directionality shows a reversal compared to the results of the (chiral Au NC)–NW\nstructures. The distance between the chiral Au NC and the Ag NW is a critical parameter that\ncan significantly modulate the plasmon coupling between the nanoparticle and the NW.\nSupplementary Fig. 23 | SPP propagation in the (chiral Au NC)@SiO –(Ag NW)\n2\nstructures. a SEM images of an (L-handed chiral Au NC)@SiO –(Ag NW) structure. b\n2\nstructure (i) and pseudocolor images for the illumination of LCP (ii), RCP (iii), and linearly\npolarized laser light (iv). The direction of linear polarization is perpendicular to the long axis\nof the NW. The LCP and RCP laser light were directionally coupled toward the LO (red box)\nand RO (yellow box) of the NW, respectively. The linearly polarized laser light was\ndirectionally coupled toward the RO (yellow box) of the NW. c SEM images of a (D-handed\nchiral Au NC)@SiO –NW structure. d Pseudocolor dark-field microscopy image of the (D-\n2\nhanded chiral Au NC)@SiO –NW structure (i) and pseudocolor images for the illumination of\n2\nlinearly polarized laser light (ii). The linearly polarized laser light was directionally coupled\nPage 12 of 26\ntoward the LO (red box) of the NW. e Normalized intensities of the LO and RO in the (L-\nhanded chiral Au NC)@SiO –NW structures under the excitation of LCP/RCP light. The data\n2\nwere collected and averaged from 3 L-handed structures. f, g Normalized intensities of the LO\nand RO in the (L-/D-handed chiral Au NC)@SiO –NW structures (f) and directionality of the\nand averaged from 3 L-/D-handed structures.\nThe effect of the shell thickness of the (L-handed chiral Au NC)@SiO nanoparticles on the\n2\ndirectional SPP propagation of the hybrid structures was further examined through simulations.\nUnder LCP/RCP excitation, a 15-nm SiO shell leads to a reversed photonic spin‑Hall effect,\n2\nwhere SPPs propagate along the –x direction for an LCP dipole and +x direction for an RCP\ndipole (Supplementary Fig. 24a). Although the SiO shell preserves the chiroptical response of\n2\nthe chiral Au NC core, it modifies the near‑field coupling of the nanoparticle to the NW. The\npropagating directions for LCP/RCP exciting light are reversed when the chiral NC is coated\nwith a 15-nm SiO shell. The simulations showed that tuning the shell thickness can also switch\n2\nthe SPP direction for linearly polarized dipoles. Reducing the SiO thickness from 10 nm to\n2\n5 nm results in a reversal of the SPP propagation direction, from +x to –x (Supplementary Fig.\n24b).\nSupplementary Fig. 24 | Simulations of the electric field of the (L-handed chiral Au\nNC)@SiO –(Ag NW) structures with different shell thicknesses. a Distributions of the\n2\nelectric field enhancement in an x-y plane monitor located at the bottom surface of the Ag NW\nin the (L-handed chiral Au NC)@15-nm-SiO –(Ag NW) structure under the excitation of\n2\ncircularly and linearly polarized dipole sources. SPPs propagate along the –x direction for the\nLCP dipole, whereas SPPs propagate along the +x direction for the RCP dipole. b Distributions\nof the electric field enhancement for the (L-handed chiral Au NC)@SiO –(Ag NW) structures\n2\nwith different shell thicknesses under the excitation of linearly polarized dipole sources. The\nSiO thicknesses are 10 nm, 5 nm, and 2 nm, respectively. SPPs propagate preferentially along\n2\nthe +x direction when the shell thickness is 10 nm or 15 nm. Reducing the SiO thickness from\n2\n10 nm to 5 nm results in a reversal of the SPP propagation direction, from +x to –x.\nWe have added discussion on the effect of the distance between the chiral Au NC and the NW\nto the end of the paragraph right before the section of “Chirality-dependent routing of the valley\nexcitons in WS2 monolayers”.\nPage 13 of 26\n“…… The SPPs in the NW can therefore be routed under the excitation of linearly polarized\nlight depending on the chiroptical properties of the attached chiral nanoparticle. To investigate\nthe effect of the distance between the chiral Au NC and the Ag NW on the SPP propagation,\nthe chiral Au NCs were coated with a 15-nm-thick SiO shell (Supplementary Fig. 23). The\n2\ncompared to the results of the (chiral Au NC)–NW structures. The simulation results reveal\nthat tuning the SiO thickness (e.g., from 10 nm to 5 nm) can switch the SPP propagation\n2\ndirection under linearly polarized excitation (Supplementary Fig. 24). The SPP routing depends\nnot only on the chiroptical property of the nanoparticle but also on its plasmon coupling with\nthe NW.”\nThe preparation of the (chiral Au NC)@SiO nanoparticles has been added into Methods.\n2\nmesostructured SiO shell onto the chiral Au NCs through the hydrolysis of tetraethyl\n2\northosilicate (TEOS). The chiral Au NC sample was washed to remove extra CTAB and\nredispersed in water (1 mL). NaOH (0.1 M, 10 µL) and CTAB (0.1 M, 10 µL) solutions were\nthen added. A SiO precursor was prepared by mixing TEOS (1 mL) with ethanol (9 mL).\nNC dispersion every 20 min. After the addition of the precursor solution in 1 h (a total of 30\nµL of the precursor solution added), stirring was continued for 5 h to allow for the hydrolysis\nand formation of a mesostructured SiO shell. The obtained nanoparticle sample was finally\n2\nwashed twice and redispersed in water.\n(2) To clarify the effect of the distance between the plasmonic nanostructure and the WS\n2\nmonolayer on the exciton emission dynamics, we have added related simulations on the\npumping and decay rates of the hybrid structure.\nThe simulation settings were consistent with those in Fig. 5, with the only modification being\nthe z-positions of the monitor, dipole sources, WS monolayer, and substrate to control the\n2\ndistance d between the bottom surface of the (chiral Au NC)–(Ag NW) structure and the WS\n2\nmonolayer. The results indicate that the directionality arising from the chirality-dependent SPP\ncoupling remains robust across different d of 6–10 nm. The simulated pumping and decay rates\n(P and Γ) of the structures with different d are shown in Fig. R1.\nThe LCP and RCP components of the electric field (P and P ) for the (L-handed chiral\nLCP RCP\nAu NC)–NW structure under 594 nm linearly polarized excitation are responsible for the\npumping rates of excitons from the +K and −K valleys. The asymmetric distributions of both\nP and P remain consistent for the cases of d = 6 nm, 8 nm, and 10 nm, whereas their\nLCP RCP\nintensities slightly decrease with increasing d (Fig. R1a).\nThe decay rates of LCP and RCP dipoles (Γ and Γ ) were also simulated to estimate the\nLCP RCP\nmetal-induced nonradiative damping with increasing d (Fig. R1b–e). The circularly polarized\ndipole was located at four locations in the x-y plane (xy-1, 2, 3, 4, indicated by the white dots\nin Fig. R1a) and at different z positions corresponding to d values ranging from 5 nm to 14 nm.\nThe values of Γ and Γ increase with increasing d at all xy positions, whereas the relative\nLCP RCP\nintensity ratio between Γ and Γ remains unchanged. This trend indicates a reduction in\nLCP RCP\nnon‑radiative quenching and the preservation of the chiral asymmetry as d is increased.\nPage 14 of 26\nFig. R1 | Simulated pumping and decay rates of the (L-handed chiral Au NC)–(Ag NW)-\non-WS structure for different distances. a Distributions of P and P in the x-y plane\nfor different distances d of 6 nm, 8 nm, and 10 nm under the excitation of the 594 nm linearly\npolarized Gaussian beam. d is the distance between the bottom surface of the (L-handed chiral\nAu NC)–(Ag NW) structure and the WS monolayer. b–e  and  for different d values\nunder the excitation of LCP and RCP dipoles placed at varying positions of 1 (b), 2 (c), 3 (d),\nand 4 (e) in the x-y plane, respectively. The locations of the dipoles in the x-y plane are marked\nin (a).\nTo evaluate the effect of the plasmonic proximity on WS excitonic emissions, we introduced\n2\na 6-nm-thick Al O spacer between the Ag NW and the WS monolayer (Fig. R2). When a 514\n2 3 2\nnm laser was focused either on the lower or upper side of the NW, directional propagation\nremained absent under linearly polarized excitation, indicating no pronounced asymmetric\nexcitonic emissions induced by the Ag NW under these conditions.\nPage 15 of 26\nFig. R2 | PL spectra of the outputs in the (Ag NW)-on-(WS monolayer/6-nm-Al O )\n2 2 3\nstructure under the excitation of linearly polarized laser light. a, b Pseudocolor image (a)\nand PL spectra of the LO and RO (b) for the illumination of linearly polarized laser light at the\nlower position of the NW. c, d Pseudocolor image (c) and PL spectra of the LO and RO (d) for\nthe illumination of linearly polarized laser light at the upper position of the NW.\nResponse to Reviewer #2\nComments: Directional light splitting based on the photonic spin-Hall effect is demanding for\nthe development of spin-dependent optical elements but still greatly missing. Here we report\non the routing of surface plasmon polaritons (SPPs) by use of chiral Au nanocubes (NCs).\nExperiments and theoretical modeling have been performed to understand the photonic spin-\nHall effect in an Ag nanowire (NW) under excitation of circularly polarized light. The SPPs in\nthe Ag NW can be modulated by the attached chiral Au NCs with opposite chiralities under\nexcitation of linearly polarized light. Hybrid structures are further constructed out of (chiral\nAu NC)-(Ag NW) assemblies and transition metal dichalcogenide monolayers to selectively\ninduce directional emissions of valley-polarized excitons and enhance the degree of valley\npolarization. The research group has good experimental equipment and proficient operational\nskills. Many drawing details expressions are need modified.\nResponse: We thank the reviewer for their positive assessment of the significance of our work\nand for acknowledging the experimental effort.\nQuestion 1: In the caption of Figure 1 (e), directly using CPL to describe the experimental\ndesign lacks guidance. It is suggested to make the following two modifications:\n1) supplement the previous text to clarify that CPL has two chirality, namely LCP/RCP.\n2) clarify in the relevant discussion of Figure 1 (e) that the experiment was conducted\nseparately by LCP and RCP.\nResponse: We thank the reviewer for the valuable suggestions. We have clarified the\ndescription of CPL in the paragraph right after Fig. 1 and in the third paragraph after Fig. 3 for\nthe relevant discussion of Fig. 1e.\nPage 16 of 26\n“The chiral Au NC in a (chiral Au NC)–(Ag NW) structure was illuminated by a LCP or RCP\nlaser beam at the wavelength of 633 nm (Fig. 1c). The scattered laser light at ……”\n“…… The normalized intensities of the LO and RO collected from three representative (D-/L-\nhanded chiral Au NC)–NW devices excited separately by LCP and RCP laser light are\nsummarized in Fig. 1e. The selected regions of the LO and RO in ……”\nQuestion 2: Taking Figure 2 (b) as an example, it is recommended to use two different colors,\nred and blue, to distinguish between LCP and RCP light sources with different chirality.\nResponse: We thank the reviewer for this valuable suggestion. The color of RCP light in Fig.\n2b has been changed to blue.\nPage 17 of 26\nQuestion 3: The article does not discuss the chirality of gold nanocubes. How is their chirality\ndetermined through SEM images? I suggest the author can clearly indicate or supplement the\nsynthesis pathway, or provide corresponding chiral optical effects that can be distinguished. It\nis recommended that the author refer to the judgment methods of relevant research on the\nsynthesis of this particle for discussion and supplementation.\nResponse: We thank the reviewer for these helpful suggestions. The chirality of the chiral Au\nNCs was determined by their morphological handedness observed in their SEM images and\nextinction asymmetry factor (g-factor).\nPage 18 of 26\nThe SEM images of the chiral Au NCs in Supplementary Fig. 2b, c exhibit a distinct twisted-\narm structure with fourfold rotational symmetry. The curvature direction of a half-ring along\nthe arm, clockwise or counterclockwise, can be assigned as D- or L-handedness, respectively\n(Supplementary Fig. 2b). The D- and L-handed Au NC samples were synthesized through seed-\nmediated overgrowth on Au nano-octahedra in the presence of chiral glutathione (GSH)\nmolecules, which directed asymmetric growth on high-Miller-index facets. The detailed\nsynthesis method can be found in Methods. The resultant handedness of the chiral nanoparticles\nwas confirmed by circular dichroism (CD) spectroscopy. The aqueous dispersions of the D-\nand L-handed chiral Au NCs exhibit opposite CD signals across the wavelength range of 500–\n800 nm, with a measured ensemble extinction g-factor of up to ~0.18. The extinction g-factor\nis defined as g = 2 × (E – E )/(E + E ), where E and E are the extinction\next LCP RCP LCP RCP LCP RCP\nintensities of the aqueous chiral Au NC sample under the excitation of LCP and RCP light,\nrespectively. The aqueous D-handed chiral Au NC sample exhibits a positive extinction g-\nfactor band in 520–650 nm, while the L-handed chiral Au NC sample exhibits a negative\nextinction g-factor band. The extinction g-factor spectra can be found in Fig. 1c of our\npublished work (ACS Nano 2024, 18, 383).\nThe determination of chirality through SEM imaging has been added in Supplementary Fig. 2b.\nSupplementary Fig. 2 | (Chiral Au NC)–(Ag NW) structures. a Schematic of the assembling\nprocess of the (chiral Au NC)–NW structures. b, c SEM images of the (D-handed chiral Au\nNC)–NW (b) and (L-handed chiral Au NC)–NW structures (c). The chiral Au NC sample\nexhibits a distinct twisted-arm structure with fourfold rotational symmetry. The curvature\ndirection of a half-ring along the arm, clockwise or counterclockwise, can be assigned as D- or\nL-handedness, respectively.\nWe have added the synthesis method of the chiral Au NCs into the first paragraph of Results.\n“The (chiral Au NC)–NW hybrid waveguides were fabricated by assembling chiral Au NCs\nwith distinct chiral morphologies on as-prepared Ag NWs that were deposited on Si/SiO\nsubstrates (Supplementary Figs. 1, 2). D- and L-handed Au NCs were synthesized through\nseed-mediated overgrowth on Au nano-octahedra in the presence of chiral molecules, which\ndirected asymmetric growth on high-Miller-index facets. The Ag NW with a single attached\nchiral Au NC can be found on ……”\nQuestion 4: Supporting Figure S8(a) suggest placing the coordinate axis at the front to help\nreaders read and understand.\nResponse: We thank the reviewer for the useful suggestion. The coordinate axis in\nSupplementary Fig. 8a (now Supplementary Fig. 11a) has been added.\nQuestion 5: Will this quadrilateral structure have resonance problems like previous studies in\nFigure S17? Ref: L. Shan, F. Zhang, J. Ren et al. Large Purcell enhancement with nanoscale\nnon-reciprocal photon. transmission in chiral gap-plasmon-emitter systems. Opt Express, 2020,\n28(23): 33890-33899.\nResponse: We thank the reviewer for this insightful question. In the previous work (Opt.\nExpress 2020, 28, 33890), unidirectional CPL transmission is achieved through switching\nbetween two distinct plasmon resonance modes, which is enabled by varying the side length of\nthe coupled plasmonic nanoblock. Such an eigenmode switching leads to a reversal of the\npropagation direction for the same CPL excitation.\nIn contrast, the chiral Au NCs used in our study were synthesized with highly uniform sizes.\nThey support a single and stable plasmon resonance mode at our operation wavelength of 633\nnm. Switching between two distinct plasmon resonance modes does not occur in our work.\nPage 20 of 26\nQuestion 6: The structure of WS and silver nanowires can also cause directional propagation\n2\nwhen incident by CPL. Will linearly polarized light incident in the article also have a similar\neffect? I hope the author can further discuss this issue. If linearly polarized light directly\nirradiates the WS line structure without causing directional propagation, it directly proves the\n2\noptical effect of gold nanostructures; If it will lead to directional propagation, the author needs\nto supplement the discussion on how to avoid the influence of silver nanowires on the\nexperimental results when designing the experiment (such as removing only gold nanoparticles\nto see if the propagation direction will be affected).\nResponse: We conducted the control experiment by studying the PL propagation in a (Ag\nNW)-on-WS structure (Supplementary Fig. 29). The 514 nm laser light was focused on the\n2\nupper side of the NW with a lateral offset of ~150 nm from its center. Under linear\npolarization excitation, the PL outputs from the LO and RO of the NW remained\nsymmetric, regardless of whether the polarization was perpendicular or parallel to the long\naxis of the NW (Supplementary Fig. 29b, c). This is because linearly polarized light can be\ndecomposed into equal LCP and RCP components, which excite symmetric near‑field\ndistributions when no chiral scatterer is present.\nEven under LCP/RCP excitation, the (Ag NW)-on-WS structure alone showed negligible\n2\ndirectionality under our experimental configuration (Supplementary Fig. 29d, e). As noted in a\nprevious work (Science 2018, 359, 443), a pronounced directional response for a (Ag NW)-on-\nWS structure requires the excitation spot to be offset by ~500 nm from the NW center. This\n2\ncondition was not met with our measurements. In our experiments, the laser was focused on\nthe interface between the chiral Au NC and the Ag NW. The resultant strong near-field\nconfinement localized the electromagnetic field to the gap region.\nThe polarization‑resolved PL spectra under linear polarization excitation further confirmed\nminimal DCPs at the outputs (Supplementary Fig. 29f, g).\nIn summary, these control experiments demonstrate that the chiral Au nanoparticle is essential\nfor achieving the directional PL routing observed in our hybrid structures. The Ag NW or WS\n2\nmonolayer alone, under the same excitation geometry, does not produce directional responses.\nPage 21 of 26\nSupplementary Fig. 29 | PL spectra and polarization-resolved PL spectra of the outputs\nin the (Ag NW)-on-(WS monolayer) structure under 514 nm laser excitation. a\nlaser was focused on the upper side of NW with a lateral offset of ~150 nm from its center. b,\nc PL spectra collected from the LO and RO under linear polarization excitation, with\npolarization perpendicular (b) and parallel (c) to the long axis of the Ag NW. d, e PL spectra\nof the LO and RO for the illumination of LCP (d) and RCP (e) laser light. f, g Polarization-\nresolved PL spectra of LO (f) and RO (g) for the illumination of linearly polarized laser light.\nThe laser power in (f, g) was increased 30‑fold to improve signal‑to‑noise ratio. The PL outputs\nfrom the LO and RO of the NW remained symmetric under linear or circular polarization\nexcitation. The difference between the LCP and RCP components of LO/RO was minimal.\nWe have added discussion on the PL propagation in achiral structures to the end of the\nparagraph right before Fig. 4.\nPage 22 of 26\n“…… The absolute DCP values of the ROs are higher than those of the LOs for both the L-\nhanded and D-handed structures. To further clarify the essential role of chiral plasmonic\nnanoparticles, we conducted a series of control experiments using a bare (Ag NW)-on‑WS\n2\nstructure without any attached nanoparticle and (achiral Au NC)–NW‑on‑WS structures\n2\n(Supplementary Figs. 29–31). In all control cases, whether no particle, a single achiral Au NC,\nor an achiral Au NC dimer was attached, the PL intensities from the LO and RO showed\nnegligible differences under linear polarization excitation, and the DCP remained close to zero.\nThese results confirm that the chiral Au nanoparticle is essential for achieving the observed\ndirectional routing of PL. In contrast, achiral hybrids or the NW alone do not support\ndirectional output under the same excitation geometry.”\nQuestion 7: Can we discuss the impact of geometric positions? How to control the relative\nposition of gold and silver in the experiment? If the experiment cannot be controlled, should\nwe consider adding relevant simulations for theoretical calculations?\nResponse: We thank the reviewer for raising this important point regarding the control and\nimpact of the nanoparticle–NW distance. This question was also raised by Reviewer #1 in\nQuestion 5. To address this point, we have performed additional experiments and simulations.\nThe detailed descriptions of new Supplementary Figs. 23, 24 can be found on pages 11–14 in\nthis response letter. We introduced a 15-nm-thick SiO shell onto the surface of the chiral\nAu NC)@SiO –NW structures (Supplementary Fig. 23). The results show that the output\n2\ndirectionality under linearly polarized excitation can be reversed compared to the bare (chiral\nAu NC)–NW structures with the same handedness, confirming that the nanoparticle–NW\ndistance strongly affects the plasmon coupling. We have further conducted simulations on the\nSPP propagation of the (chiral Au NC)@SiO –NW structures with varying SiO shell\n2 2\nthicknesses (Supplementary Fig. 24). Tuning the shell thickness of the attached (chiral\nAu NC)@SiO nanoparticles can switch the preferred SPP propagation direction.\nthe section of “Chirality-dependent routing of the valley excitons in WS2 monolayers”.\n“…… The SPPs in the NW can therefore be routed under the excitation of linearly polarized\nlight depending on the chiroptical properties of the attached chiral nanoparticle. To investigate\nthe effect of the distance between the chiral Au NC and the Ag NW on the SPP propagation,\nthe chiral Au NCs were coated with a 15-nm-thick SiO shell (Supplementary Fig. 23). The\n2\ncompared to the results of the (chiral Au NC)–NW structures. The simulation results reveal\nthat tuning the SiO thickness (e.g., from 10 nm to 5 nm) can switch the SPP propagation\n2\ndirection under linearly polarized excitation (Supplementary Fig. 24). The SPP routing depends\nnot only on the chiroptical property of the nanoparticle but also on its plasmon coupling with\nthe NW.”\nQuestion 8: In this study, the optical properties of gold nanocubes were limited to the\nconversion of linearly polarized light. The article also mentioned the enhancement effect of the\nPage 23 of 26\nstructure’s composition on electromagnetic fields. Can Raman and other optical properties be\nfurther studied?\nResponse: We thank the reviewer for raising this interesting point. We have verified the broad\napplicability of chirality‑dependent routing using R640 molecules coupled to the (chiral Au\nNC)–(Ag NW) structures (Supplementary Fig. 33). The chiral Au NCs were coated with R640\nand assembled onto the surface of the Ag NW (Supplementary Fig. 33a, d). Under linearly\npolarized excitation, the PL from R640 exhibited directional SPP propagation that depended\non the handedness of the attached chiral Au NC. The D‑handed structure routed the PL\npreferentially toward the LO, whereas the L‑handed structure routed it toward the RO\n(Supplementary Fig. 33b, e). The normalized intensity and the directionality of the outputs,\ncollected from 3 devices for each handedness, showed opposite propagating directions for the\nD- and L-handed structures (Supplementary Fig. 33c, f, g, h).\nSupplementary Fig. 33 | Directional PL from the R640‑coupled (chiral Au NC)–NW\nstructures under the excitation of linearly polarized laser light. a, b SEM images of a (D-\nhanded chiral Au NC)@R640–(Ag NW) structure (a) and PL spectra of the LO and RO (b).\nThe direction of linear polarization of the laser light is perpendicular to the long axis of the Ag\nNW. The fluorophore molecules were embedded in a mesostructured SiO shell surrounding\nthe chiral Au NC. c Directionality of the SPP propagation of 3 (D-handed chiral Au\nNC)@R640–(Ag NW) structures. d, e SEM images of a (L-handed chiral Au NC)@R640–(Ag\nNW) structure (d) and PL spectra of the LO and RO (e). f Directionality of the SPP propagation\nof 3 (L-handed chiral Au NC)@R640–(Ag NW) structures. g, h Normalized intensities of the\nLO and RO in the (D-/L-handed chiral Au NC)–NW structures (g) and averaged directionality\nof the PL SPP propagation (h). The data were collected and averaged from 3 (L-/D-handed\nchiral Au NC)–NW structures at the wavelength of 606 nm.\nTo further validate spin‑dependent routing in the fluorescent system, we also examined the\nR640‑coupled chiral structures under circular polarization excitation (Supplementary Fig. 34).\nUnder LCP/RCP excitation, the D‑handed structure exhibited PL propagation toward the LO,\nwith a more pronounced difference between the LO and RO under LCP than under RCP\nillumination (Supplementary Fig. 34a, b). In contrast, the L‑handed structure showed reversed\npropagation and a greater output asymmetry under RCP than under LCP illumination\n(Supplementary Fig. 34c, d). This enantiomer‑specific response confirms that the chiral\nplasmon–emitter coupling also imposes spin-selective fluorescent emissions and directional\npropagation. The chirality-dependent photonic spin-Hall effect can effectively direct not only\nexcitonic emissions in WS monolayer but also fluorescence from molecular emitters,\n2\nsupporting the generalizability of the observed chirality‑dependent routing.\nSupplementary Fig. 34 | PL spectra of the outputs in the (D-/L-handed chiral Au\nNC)@R640–NW structures under the excitation of circularly polarized laser light. a, b\nPL spectra of the LO and RO of a (D-handed chiral Au NC)@R640–(Ag NW) structure for the\nillumination of LCP (a) and RCP (b) laser light. The D‑handed structure exhibits PL\npropagation toward the LO. The difference between the LO and RO under LCP excitation is\nlarger than that under RCP excitation. c, d PL spectra of the LO and RO of a (L-handed chiral\nAu NC)@R640–(Ag NW) structure for the illumination of LCP (c) and RCP (d) laser light.\nPage 25 of 26\nThe L‑handed structure exhibits PL propagation toward the RO. The difference between the\nLO and RO under RCP excitation is larger than that under LCP excitation.\nWe have added the experimental results in the paragraph right before Discussion.\n“As an extended demonstration of chirality‑dependent routing, we embedded fluorophore\nmolecules R640 in the SiO shell surrounding the chiral Au NC and studied the PL SPP routing\n2\nof R640 molecules (Supplementary Figs. 33, 34). Under linearly polarized excitation, the R640\nemissions exhibit directional SPP propagation that reverses with the handedness of the attached\nchiral NC. The D‑handed structures route the fluorescence preferentially toward the LO,\nwhereas the L‑handed structures route it toward the RO. Under LCP/RCP excitation, the\nD‑handed structures exhibit a more pronounced difference between the LO and RO under LCP\nthan under RCP illumination, while the L‑handed structures show a greater output asymmetry\nunder RCP than under LCP illumination. These results confirm that the chiral plasmon–emitter\ncoupling imposes a spin‑selective directionality not only on excitonic emissions but also on\nmolecular fluorescence emissions, underscoring the generality of chirality‑dependent routing.”\nThe preparation of the (chiral Au NC)–fluorophore nanoparticles have been included in\nMethods.\nPreparation of the (chiral Au NC)–fluorophore nanoparticles\nThe (Chiral Au NC)–fluorophore nanoparticles were synthesized with a modified procedure to\nincorporate the R640 fluorophore into the mesostructured SiO shell. The process began\n2\nidentically, with the washing and redispersion of the chiral Au NCs and the addition of the\nsame NaOH and CTAB solutions. The key difference was in the preparation of the precursor\nsolution. R640 (50 mg) was first dissolved in ethanol (5 mL), and the resultant solution was\nthen mixed with TEOS (1 mL) and ethanol (4 mL) to form a fluorophore-containing SiO\n2\nprecursor. The same protocol (3 µL every 20 min for 1 h) was then executed, which was\nfollowed by stirring for a total time of 5 h. The SiO shell formed on the surface of the chiral\nredispersed in water.\nQuestion 9: figure 1 D-hand and L-hand’s color bar have different value, why is the same\nvalue?\nResponse: We thank the reviewer for raising this question. The identical ranges of values in\nFig. 1e for both D‑ and L‑handed structures arise because the images display the normalized\nintensities, rather than the raw absolute signals acquired by the camera.\nThe normalization procedure is as follows. The photon counts from the LO and RO were first\nobtained by a fitting process as shown in Supplementary Fig. 4 and then divided by their\nacquisition time durations to obtain the intensities of I and I . We then calculated the\nLO RO\nnormalized intensity for each output. The normalized I equals I /(I + I ). The normalized\nLO LO LO RO\nI equals I /(I + I ). The same range of 0–1 of the normalized intensities can therefore be\nRO RO LO RO\nused to compare the contrast between the LO and RO.\nPage 26 of 26"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The revised version has addressed the comments, and the manuscript has been improved accordingly. I think it could be accepted for publication now.", "reviewer_2": "Directional light splitting relying on the photonic spin-Hall effect is crucial for spin-dependent optical elements yet remains largely unexplored, and this work reports the routing of surface plasmon polaritons (SPPs) using chiral Au nanocubes (NCs). Experiments and theoretical modeling are conducted to investigate the photonic spin-Hall effect in Ag nanowires (NWs) under circularly polarized light excitation, and linearly polarized light-driven SPPs in Ag NWs can be modulated by attached chiral Au NCs with opposite chiralities. Hybrid structures composed of chiral Au NC-Ag NW assemblies and transition metal dichalcogenide monolayers are constructed to selectively trigger directional emissions of valley-polarized excitons and boost valley polarization degree, whose routing mechanism is clarified via numerical simulations and holds great significance for valleytronic circuit development.\nThe quality of the data is technically sound and presented in sufficient detail.\nThe level of support for the conclusions are sufficiently strong evidence is provided for the authors’ claims and all appropriate controls have been included.\nthese results will be important to the field and advance understanding in a way that will move the field forward."}, "author_response": "Response to Reviewer #1\nComments: The revised version has addressed the comments, and the manuscript has been\nimproved accordingly. I think it could be accepted for publication now.\nResponse: We thank this reviewer for the effort on evaluating our work again, the highly\npositive comment, and the great help in the improvement of our manuscript.\nResponse to Reviewer #2\nComments: Directional light splitting relying on the photonic spin-Hall effect is crucial for\nspin-dependent optical elements yet remains largely unexplored, and this work reports the\nrouting of surface plasmon polaritons (SPPs) using chiral Au nanocubes (NCs). Experiments\nand theoretical modeling are conducted to investigate the photonic spin-Hall effect in Ag\nnanowires (NWs) under circularly polarized light excitation, and linearly polarized light-\ndriven SPPs in Ag NWs can be modulated by attached chiral Au NCs with opposite chiralities.\nHybrid structures composed of chiral Au NC-Ag NW assemblies and transition metal\ndichalcogenide monolayers are constructed to selectively trigger directional emissions of\nvalley-polarized excitons and boost valley polarization degree, whose routing mechanism is\nclarified via numerical simulations and holds great significance for valleytronic circuit\ndevelopment.\nThe quality of the data is technically sound and presented in sufficient detail. The level of\nsupport for the conclusions are sufficiently strong evidence is provided for the authors’ claims\nand all appropriate controls have been included. These results will be important to the field\nand advance understanding in a way that will move the field forward.\nResponse: We thank this reviewer for the effort on evaluating our work again, the highly\npositive comment, and the great help in the improvement of our manuscript.\nPage 1 of 1"}]

Decision letter