Spin-exciton coupling modified by interfacial magnetic interactions in a van der Waals heterostructure

Domain: physics
Published: 2026-02-10
Editorial outcome: major_revision

Abstract
Excitons are primary elementary excitations in solids that present both fundamental interest and technological importance, showing great potential for photospintronic and quantum transduction applications. The emerging coherent collective excitations in two-dimensional antiferromagnetic semiconductors raise prospects for spin-exciton interactions and multifield control schemes. However, realizing the arbitrary manipulation of excitonic quantum states, while preserving the inherent dynamic and response advantages of antiferromagnetic nature remains challenging. Here we achieve bidirectional modulation of the CrSBr exciton energy via interfacial interaction-modified spin-exciton coupling in a CrSBr/Fe3GaTe2 heterostructure. Compared with pristine CrSBr, the photoluminescence peaks in the heterostructure can exhibit blueshift and redshift corresponding to 6.1% and 8.6% of the total bandwidth, respectively. We reveal that the interfacial charge-transfer-driven magnetic coupling in the heterostructure effectively enhances the magnetic anisotropy and the exchange interaction of CrSBr, thereby stabilizing its antiferromagnetic spin configuration, suppressing interlayer electron-hole recombination, and ultimately leading to an anomalous blueshift of the exciton emission. Our findings demonstrate an approach for bidirectionally modulating exciton energy in two-dimensional antiferromagnetic semiconductors, which provides substantial flexibility in device design and offers an avenue for potential wavelength control in quantum information and optoelectronic technologies.

Introduction
Excitons, as quantized bound states of electron-hole pairs in semiconductors, have become a central research focus for next-generation optoelectronic devices and quantum technologies1–5 due to their unique photoexcitation and energy transfer properties6,7. Exciton states can strongly couple with external fields at the level of spin, valley, and orbital degrees of freedom, translating their quantum characteristics into macroscopically controllable functionalities8–13. Consequently, the incorporation of magnetism and semiconductor electronics14–16 offers exciting prospects for exploring fundamental excitation phenomena, as well as driving the unification of charge and spin manipulation and the engineering of hybrid spintronic-photonic devices. Recently, two-dimensional (2D) van der Waals (vdW) antiferromagnetic (AFM) semiconductors have provided a promising candidate for studying exciton dynamics, due to the emerging spin-orbit-entangled many-body states17,18, along with their terahertz resonance frequency19, ultrafast dynamic response20,21, and strong anti-interference capability in optimizing the lifetime and stability of excitons22,23. In addition, the strong coupling effect between the magnetic order and exciton enables the formation of a magnon-exciton coupling state, which expands the horizon of 2D materials, particularly enticing for the applications that exploit coherent magnons as energy-efficient information carriers16 in opto-spintronics and magnonics, or as interconnects in hybrid quantum systems24. Nevertheless, achieving controllable tunability of excitonic optical properties through magnetic field engineering, so as to address the demands of multi-scenario applications, remains a critical challenge in current photoelectronic technology.

CrSBr is an air-stable vdW layered AFM material with a direct semiconductor bandgap of approximately 1.5 eV25,26, which thus potentially endows the simultaneous modulation of optical and magnetic behaviors. Correspondingly, some pioneering works27–31 have revealed the tunability of electron transport properties and exciton energies within the magnetic phase. These observations suggest a strong relevance between the magnons and excitons in a single CrSBr system, rendering it ideal for exploring the coherent coupling state. Note that the coupling of Wannier excitons to magnetic order in CrSBr comes from the spin-dependent electron-exchange interactions32,33. By applying an external magnetic field, one can foresee the identical coherent behavior that a spin wave may coherently modulate the electronic structure, which is reflected in the dominant excitonic transitions in a 2D semiconductor. The altering excitonic photoluminescence (PL) under spin order modulation of the magnetic field in CrSBr validate the feasibility of tailoring interlayer electronic and exciton effects by manipulating magnetic order34,35. However, to date, such manipulation is confined solely to a single CrSBr system, which not only demands the complicated application of gate voltage36,37 and external magnetic field apparatus38,39, but is also intrinsically dominated by the emergence of ferromagnetic (FM) order, thereby disregarding the unique AFM advantages inherent to CrSBr40–42. More critically, existing methodologies are limited exclusively to unidirectional modulation towards reducing exciton energy33–35,38, and have not yet achieved bidirectional reversible modulation. Note that the pseudospin induced by the magnetic proximity interactions can provide a significantly higher interfacial coupling field than the external effective magnetic field43,44, while few studies have focused on exploring this strategy to manipulate the exciton emission of CrSBr. This hinders the opportunities to unlock more possibilities for tuning its optical and electronic properties, limiting the advancement of CrSBr-based devices and applications. Moreover, such AFM/FM heterostructure architectural design potentially serves as a fundamental building block for next-generation excitonic devices. Our work extends this field into new territory by constructing and exploiting magnetic exchange interactions in a vdW magnetic heterostructure.

Here, we report interfacial magnetic interaction-modified spin-exciton coupling in a 2D magnetic heterostructure formed by CrSBr and Fe3GaTe2 (FGT). The features of exciton PL in CrSBr exhibit a tight dependence on the magnetic transition temperatures of both CrSBr and FGT, suggesting the existence of spin-exciton coupling. In contrast to the common PL redshift in CrSBr, we demonstrate that the exciton energy exhibits an anomalous blueshift, originating from the compression of interlayer electron-hole recombination induced by interfacial magnetic interaction. Through magnetotransport tests, we demonstrate that the magnetic properties of both FGT and CrSBr are modulated by the interfacial interaction. Furthermore, in combination with microscopic-level synchrotron X-ray photoemission electron microscopy (XPEEM), we reveal an orbital-mediated charge transfer mechanism (from Fe eg-orbital to Cr t2g-orbital) for the interfacial magnetic interaction between CrSBr and FGT, which alters the magnetic domain of CrSBr. Micromagnetic simulations combined with theoretical calculations further support that the observed excitonic blueshift originates from the suppression of interlayer electron-hole recombination driven by interfacial magnetic interactions. Our work provides an approach for designing coherent behavior between spin and exciton, offering new insights into the potential application of AFM semiconductors, exemplified by CrSBr, in the field of opto-spintronics.

Results
Structure and physical properties of CrSBr/FGT heterostructure
We synthesized high-quality CrSBr and FGT single crystals (Figs. S1–S4) and fabricated the CrSBr/FGT heterostructure by using few-layer flakes exfoliated from their bulk. Figure 1a presents a schematic illustration of the stacking structure and incorporation coupling between different spin orders in the heterostructure. To explore spin-related coupling behavior, we first characterized the magnetic properties of CrSBr and FGT, as shown in Fig. 1b, c, respectively. According to temperature-dependent magnetization (M–T) tests, CrSBr exhibits a typical AFM nature with the Néel temperature TN = 130 K, while FGT, on the other hand, exhibits robust ferromagnetism beyond room temperature. A much higher Curie temperature (TC = 350 K) of FGT allows it to constantly provide a magnetic proximity coupling effect throughout the magnetic transition process of CrSBr. The Transmission Electron Microscope (TEM) cross-sectional image (Fig. 1d) confirms the high-quality interface of the heterostructure. Then, we perform Raman measurement to validate the features of the CrSBr/FGT heterostructure, as shown in Fig. 1e. The emergence of hybrid Raman modes from both CrSBr and FGT indicates the specific characteristics of the heterostructure. The optical micrograph further provides images of the CrSBr/FGT heterostructure, as well as cross-sectional analysis (Fig. 1f). The step height of the thickness line profile suggests that CrSBr and FGT are 5 and 12 nm, respectively. Given the differences in conductivity properties, the interface between CrSBr and FGT inevitably involves electronic dynamic processes. Kelvin-probe force microscopy (KPFM) provides the spatial distributions of the surface potential in the heterostructure. As exhibited in Fig. 1g, a significant potential drop of the CrSBr in the heterostructure (~−21.7 mV), compared to the pristine one (~−50.3 mV), can be observed from the surface potential in KPFM images. This indicates that FGT acts on inducing a decreased work function and an elevated Fermi level in CrSBr, as a result of charge injection. The specific charge transfer should involve participation in interfacial magnetic interactions and associated coupling phenomena, which will be further discussed later.

Detection of spin-exciton coupling
Next, we explore the photon properties of CrSBr assisted by ferromagnetic FGT. Figure 2a, b display the contour mapping diagram for pristine CrSBr and CrSBr/FGT in the temperature range from 80 to 350 K. There is an obvious turning point in the emission energy around the TN (130 K) in CrSBr/FGT, while pristine CrSBr exhibits an almost linear variation across the entire temperature range. Furthermore, we observe that the temperature-dependent PL spectra exhibit higher photon energy (blueshift) below the TN for the CrSBr on FGT, compared to pristine CrSBr (Fig. 2c), suggesting a correlation with its AFM phase transition under the action of FGT. Such behavior of excitons modulated by magnetic ordering is recognized as the coupling between magnetic order and excitons. More critically, we perform a fitting analysis of the exciton peak shift using the power-law45 dependence of the AFM transition and yield a well-fitted result (Fig. S5), which further provides compelling evidence for spin-exciton coupling in the heterostructure. While starting from 130 K, these two kinds of PL peaks are well overlapped during the subsequent warming process, except for several abnormal cases. Within these temperature ranges, CrSBr/FGT exhibit even lower photon energies (redshift) compared to pristine CrSBr, achieving a maximum difference of around 200 K. This observation indicates that the excitonic response in the heterostructure remains sensitive to interfacial magnetic effects over an expanded temperature range, far exceeding the TN of CrSBr. This suggests that the magnetic proximity effect and residual short-range magnetic correlations25,26,30 induced by the FGT layer persist well above the intrinsic magnetic transition temperature of CrSBr.

We intuitively demonstrate the difference in PL peaks and the trend of photon energy variation with temperature in Fig. 2d, e, respectively. Compared with pristine CrSBr, a step height greater than 14 meV in photon energy is observed across the critical temperature (TN) in the heterostructure, with a bidirectional modulation magnitude of approximately 6.1% (blueshift) and 8.6% (redshift) relative to the total excitonic linewidth of ~100 meV (Fig. S6). This indicates a high tuning efficiency of exciton energy in CrSBr, achieved through spin-exciton coupling. The unusual redshift of the PL exciton energy in localized regions above TN is more reasonably attributed to short-range magnetic correlations in CrSBr induced by the underlying FGT. To clarify the specific role of charge transfer in this process, we perform the test of ultraviolet photoelectron spectroscopy (UPS) in Fig. S7, which shows that the Fermi level of FGT is higher than that of CrSBr. Therefore, upon contact, when the Fermi levels align for both FGT and CrSBr, the energy level of their conduction bands would also match up, leading to charge redistribution at the interface. Furthermore, we fabricated a heterostructure by stacking the nonmagnetic metallic material WTe2 (whose conductivity is comparable to that of FGT46,47) with CrSBr. The KPFM results (Fig. S8a) demonstrated that charge transfer still occurs between the two materials in the same direction. However, in the absence of interfacial magnetic interactions, the PL spectra (Fig. S8b, S8c) exhibit no correlation with the magnetic order of CrSBr. This further confirms that the exciton energy changes in CrSBr heterostructure cannot only be fully explained by charge transfer, but also are primarily attributed to interfacial magnetic interaction-modified spin-exciton coupling. The detailed analysis of the elevated photon energy in CrSBr/FGT, resulting from spin-exciton coupling, will be elaborated thereafter.

Altered magnetic properties by the interfacial interaction
To further probe the effect of the interfacial magnetic interactions on spin ordering and magnetic properties of CrSBr, we conducted magnetotransport tests using standard Hall bars. Figure 3a gives the schematic diagram of the fabricated device that FGT stacks onto the CrSBr, establishing direct contact between the electrode and the CrSBr. Figure 3b shows the optical photograph of the pristine CrSBr and FGT/CrSBr heterostructure device (Fig. S9). The spin orientation correlating with the interlayer tunneling determines the behavior of resistance (R) under the magnetic field, making magnetoresistance a sensitive probe to capture the spin ordering dynamics. In Fig. 3c, the temperature-dependent magnetoresistance of pristine CrSBr exhibits a correlation with the applied field, showing a specific spin-flip transition below TN. The spin-flip field (Hs), corresponding to the reorientation of spin order along the direction of fields, gradually increases as the temperature decreases. Within a low magnetic field, the spins of CrSBr interlayers antialign along the easy b-axis, leading to a high tunneling resistance. When the Hs is achieved as fully polarized spins point along the direction of the magnetic field, the uniformly aligned spins facilitate the process of tunneling. For the FGT/CrSBr heterostructure device (Fig. 3d), Hs is enhanced. This indicates that the spin orientation along the easy axis in CrSBr has been strengthened, thereby necessitating higher magnetic fields to force spin reorientation. We further identify that this strengthened spin orientation shows a strong positive correlation with the exciton energy modulation capability (Fig. S10). Besides, we also extracted the Hs and magnetoresistance ratio (MRR) from CrSBr and FGT/CrSBr devices, and plotted them as a function of temperature, as shown in Fig. 3e, f. Overall, the Hs of FGT/CrSBr are significantly larger below TN, with even more pronounced differences at low temperatures. However, the MRR of FGT/CrSBr exhibits an anomalous increase trend with the temperature below TN, which can be attributed to the interfacial magnetic coupling in CrSBr that stabilizes the spin orientation, leading to a higher magnetoresistance. This enhanced magnetoresistance may also influence the interlayer electronic interactions, potentially affecting the excitonic behavior.

In addition, we fabricated another heterostructure in which CrSBr stacks onto the FGT (Fig. S11) to explore the impact of magnetic coupling on the FGT magnetism. To clarify the signal origin, we independently measured the Hall response of CrSBr and found a negligible Hall resistance (Fig. S12), demonstrating that the Hall signals observed in the heterostructure originate solely from the FGT layer. Figure 3g presents the illustrative diagram of the Hall devices for CrSBr/FGT heterostructure, and both the optical images of pristine FGT and CrSBr/FGT are given in Fig. 3h. The Hall resistance Rxy of pristine FGT, measured under an out-of-plane field, exhibits regular square-shaped hysteresis loops in the whole temperature range from 5 K to 300 K (Fig. 3i), suggesting robust ferromagnetism that agrees with its single-crystal magnetic test results (Figs. S13, S14). With increasing temperature, the Rxy and coercivity field (Hc) gradually drop due to the thermal fluctuations. However, Fig. 3j shows a distinct evolution of Rxy and Hc for FGT in the heterostructure when interfacial magnetic coupling exists. By further extracting these data and plotting their variation with temperature, we found that the Hc of CrSBr/FGT is significantly larger than that of the pristine FGT below the temperature close to TN (Fig. 3k). Additionally, under the interfacial magnetic interaction, the Rxy of CrSBr/FGT no longer exhibits a monotonically decreasing behavior with temperature increasing, but shows a trend of increasing to around TN and then decreasing (Fig. 3l). It is evident that within the temperature range of magnetic order in CrSBr, the magnetism of FGT does indeed enhance. All these results declare that the interfacial magnetic interaction in the CrSBr/FGT heterostructure is reciprocal, which affects the magnetic properties of both CrSBr and FGT.

Interfacial magnetic interaction in the heterostructure
Given the intensive impact of magnetic coupling on spin-correlated phenomena, we further precisely investigate the features of the interfacial magnetic interaction. Element-resolved XPEEM enables ultrahigh-spatial resolution imaging to elucidate the magnetic domain structure, magnetization direction, and interlayer interactions. All XPEEM data were recorded at 100 K after zero-field cooling with normal incidence (90°) of X-ray on the sample surface. Exceptionally, Fig. 4i was measured using grazing-incidence X-ray (16°). Figure 4a gives a schematic diagram of the principle of XPEEM. According to the X-ray absorption spectroscopy (XAS) of Fe L-edge (Fig. 4b), both the L3 and L2 edges of the heterostructure shift to higher energy compared to pristine FGT, verifying its electron loss48. Moreover, the shoulder peak on the high-energy side of the L3 edge becomes more pronounced, indicating that electrons are depleted from the higher-energy, eg, orbitals, leading to an increased population of unoccupied states49,50. In Fig. 4c, Cr L-edge XAS of the pristine CrSBr exhibits a typical feature of Cr3+, whereas in the heterostructure, the shoulder peak on the low-energy side of the L3 edge is weakened, and the fine structure at the L3,2 edge disappears. These characteristics are indicative of a decrease in valence state after gaining electrons, and the features of this shoulder peak also suggest that electrons are transferred from the Fe eg-orbital to the Cr t2g-orbital in CrSBr. To further explore the evolution of the magnetic moment under the magnetic coupling, we further conducted X-ray magnetic circular dichroism (XMCD) and X-ray magnetic linear dichroism (XMLD) spectra. We then extract the Fe L-edge XMCD data from the areas marked by the red and purple rectangles in the XMCD-PEEM. As shown in Fig. 4d, e, the Fe L-edge XMCD signal of pristine FGT (−25.8%), extracted from the bright (rectangle) area in Fig. 4f, is significantly higher than that of the FGT in the CrSBr/FGT heterostructure (−18.5%). We also extract the data from the dark (circle) areas, in which a similar intensity variation of XMCD can be obtained in the opposite polarization direction (Fig. S15). This indicates that when forming a heterostructure with CrSBr, the magnetic moment of FGT is weakened. Subsequently, the XPEEM imaging of the magnetic domain at the Fe L3 edge photon energy is performed and presented in Fig. 4f. It is evident that the pristine FGT displays a typical domain, and even in the heterostructure area with CrSBr, there is no significant change in this magnetic domain phase. We further demonstrate that this magnetic domain can be well maintained up to room temperature (Fig. S16), indicating the stability of the FGT magnetic structure.

Besides, the extracted Cr XMLD signal from the XMLD-PEEM image (Fig. S17) also undergoes suppression, as it decreases from −6.9% to −4.9% (Fig. 4g, h), suggesting a reduced AFM spin moment. To directly probe the in-plane magnetic domains of CrSBr and to validate the interfacial interaction in the heterostructure, we further performed Cr L-edge XMCD-PEEM measurements under grazing-incidence geometry (16°) (Fig. 4i), which enhances sensitivity to the in-plane magnetic component of Cr moments. Notably, compared with the multidomain state of pristine CrSBr, CrSBr in the heterostructure exhibits a magnetic single-domain with decreased magnetic contrast. This direct observation clearly indicates that the enhanced magnetic domain wall energy and decreased magnetic moment for CrSBr in the CrSBr/FGT heterostructure further demonstrating the presence of interfacial magnetic interaction between CrSBr and FGT. In contrast, the Cr L-edge XMCD-PEEM acquired under normal-incidence geometry (Fig. S18) shows that the magnetic effect of the heterostructure failed to induce the appearance of observable XMCD signals at the Cr L3 edge photon energy, which demonstrates that there is no spin canting along the out-of-plane. Furthermore, according to the Cr L-edge XMLD-PEEM image (Fig. S17), we further verify that the in-plane orientation of the Néel order in both pristine CrSBr and CrSBr/FGT remains unchanged, maintaining stability along the original AFM b-axis. The absence of Néel order canting or flopping in CrSBr indicates that the observed reduction in XMLD intensity originates from a diminished magnetic moment of CrSBr. Based on the above discussion, although the interfacial magnetic interaction in the CrSBr/FGT heterostructure changes the magnetic domain of CrSBr, it does not alter the intrinsic AFM spin orientation. On the other hand, regarding the observed reduction in magnetic moments for both CrSBr and FGT within the heterostructure, an orbital-mediated electron transfer mechanism should be considered, which affects the unpaired electrons and net moments (Fig. S19). Specifically, in CrSBr, where Cr3+ ions possess three unpaired electrons in their outermost d-orbitals (each occupying a distinct t2g orbital), the introduction of extrinsic electrons through interfacial charge transfer enables pairing with these localized spins. This electron population in the t2g consequently reduces the net unpaired electron count, leading to diminished magnetic moments. For the FGT subsystem, where both Fe2+ and Fe3+ ions maintain unpaired electrons in their eg orbitals, the loss of any single electron from these degenerate orbitals thus results in a quantized decrease in spin-polarized electrons and a weakened magnetic moment. This orbital-mediated electron transfer mechanism is well supported by our XAS data (Fig. 4b, c), and the interfacial charge transfer can simultaneously modify the electronic structure of Cr, thereby exerting a profound impact on macroscopic magnetic properties. Specifically, the increased electron occupancy in Cr-3d orbitals of CrSBr enhances their electron cloud density and amplifies the spatial overlap of adjacent Cr atomic orbitals51–53, which in turn strengthens orbital hybridization, stabilizes the spin configuration, and reinforces the interfacial magnetic interaction.

Modulation mechanism of spin-exciton coupling by interfacial magnetic interaction
Lastly, we discuss the anomalous increase of exciton energy in CrSBr/FGT below TN. To understand this phenomenon from a microscopic perspective, we performed a series of theoretical calculations and simulations. Density functional theory (DFT) calculations reveal a pronounced redistribution of charge density in the CrSBr/FGT heterostructure (Fig. 5a). Quantitative charge analysis (Table S1, Supporting Information) shows an net electron transfer of approximately 0.007 e/Å2 from FGT to CrSBr, in agreement with our KPFM and XAS measurements, further confirming the existence of interfacial charge transfer. Notably, such charge transfer occurring between magnetic materials provides a crucial electronic-structure foundation for the establishment of interfacial magnetic interaction. On this basis, we further extract the spin polarization rate difference (ΔP) of CrSBr in the heterostructure from the DFT calculations (Fig. 5b), which can be expressed as ΔP = |(Nhetero_up - Nhetero_down)/Nhetero_total| - |(NCrSBr_up - NCrSBr_down)/NCrSBr_total|, where N_up, N_down and N_total denote the numbers of spin-up, spin-down and total electrons, respectively. The superscripts “hetero” and “CrSBr” refer to the CrSBr in the CrSBr/FGT heterostructure and pristine CrSBr, respectively. A positive ΔP indicates that the spin-polarized rate of CrSBr is enhanced in the heterostructure compared to pristine CrSBr, providing direct microscopic electronic-structure evidence for the modulated spin configuration of CrSBr. To further elucidate how these electronic-structure modifications influence the magnetic properties, we performed micromagnetic simulations based on parameters extracted from both experiments and theoretical calculations. Micromagnetic simulations based on MuMax354 serve as a powerful tool for capturing the evolution of magnetic energies and spin configurations in magnetic materials, particularly for our constructed heterostructure model incorporating interlayer magnetic coupling between FGT and CrSBr (Fig. S20). The simulation results demonstrate that both the magnetic anisotropy energy and the exchange interaction energy of CrSBr are enhanced in the heterostructure (Fig. 5c), which is consistent with the emergence of a magnetic single-domain of CrSBr observed in the XMCD-PEEM measurement. This elevated magnetic energy landscape effectively stabilizes the AFM spin configuration of CrSBr, which is in excellent agreement with the robust spin orientation in XMLD-PEEM and the increased spin flip field in transport measurements, and is further supported by the enhanced spin polarization rate revealed by the DFT calculations.

Combining the above experimental observations, micromagnetic simulations, and DFT calculations, we establish the following physical picture: interfacial charge-transfer-driven magnetic coupling enhances the AFM ordering of CrSBr, manifested by the concurrent enhancement of its exchange interaction and magnetic anisotropy. It is worth noting that for A-type AFM CrSBr, antiparallel spin alignment between adjacent layers strongly suppresses interlayer electron-hole recombination35. When an external magnetic field or other perturbations drive the interlayer spins into a ferromagnetically aligned configuration, spin-allowed interlayer charge transfer channels are opened, leading to enhanced interlayer electron-hole hybridization and a redshift of the exciton energy35,55. In contrast, in our CrSBr/FGT heterostructure, the interfacial magnetic interaction further strengthens the AFM order of CrSBr, thereby more effectively suppressing interlayer electron-hole recombination and significantly reducing its contribution to optical transitions (Fig. 5d). Our work ultimately gives rise to an anomalous blueshift of the exciton emission energy below TN through interfacial magnetic interaction. When the temperature exceeds the TN of CrSBr, its AFM order gradually diminishes, and the interfacial magnetic interaction-modulated ability correspondingly weakens, resulting in an abrupt change in the PL energy across the TN (Fig. 2d). In the temperature range above the TN of CrSBr but below the TC of FGT, ferromagnetically ordered FGT may still locally induce FM correlations in CrSBr, which can reopen interlayer electronic hybridization channels and lead to a redshift of the exciton energy. As the temperature is further increased beyond the TC of FGT (above 300 K), this induced effect vanishes, and the exciton energy in the CrSBr/FGT heterostructure gradually converges to that of pristine CrSBr. This tunable exciton energy between blueshift and redshift, driven by interfacial magnetic interaction-dependent spin-exciton coupling, may unlock the potential for arbitrary manipulation of exciton energies to enable precise control over the quantum states of excitons in quantum information storage.

In summary, we demonstrate the bidirectional tunability of exciton energy in a 2D CrSBr/FGT magnetic heterostructure, governed by spin-exciton coupling modified through interfacial magnetic interactions. The FM order in FGT modulates the spin configuration of CrSBr, which is consistently reflected in the evolution of magnetic-sensitive exciton energy, leading to an anomalous photon emission energy blueshift below TN. These results establish a direct correlation between interfacial spin states and exciton energy, highlighting spin-mediated control of excitonic properties in vdW heterostructures. Based on experimental measurements and theoretical simulations, we demonstrate that the interfacial charge-transfer-driven magnetic coupling in the heterostructure enhances both the magnetic anisotropy and exchange interaction of CrSBr, effectively stabilizing its AFM spin configuration, which suppresses interlayer electron-hole recombination and increases the spin-flip field. Notably, the exciton energy shift can be bidirectionally modulated between positive and negative states relative to pristine CrSBr, with the magnitude of blueshift and redshift exceeding 6% and 8% of the total bandwidth, respectively. This bidirectional control highlights significant flexibility in device design and offers a valuable reference for future studies on wavelength control in laser systems. Our findings present an effective strategy to tailor spin-exciton coherence, opening avenues for AFM semiconductors like CrSBr in opto-spintronic devices such as spin-logic gates and non-volatile magneto-optical memory systems.

Methods
Sample preparation
Single crystals of CrSBr were successfully synthesized using the chemical vapor transport (CVT) method, with iodine as the transport agent. High-purity chromium (99.9%), bromine (99.99%), and sulfur (99.99%) powders were weighed according to the stoichiometric ratio of 1:1:1, mixed, and sealed in quartz tubes inside an Ar-filled glove box. These sealed quartz tubes were then placed in a two-zone furnace, where the temperature gradient of the source and growth zones was set at 1173 K (hot zone) and 1073 K (cold zone), respectively. After one week of isothermal heating, high-quality CrSBr single crystals were successfully obtained. Single crystals of FGT were also grown by the CVT method. The CVT growth process began with a mixture of iron power (99.95%), gallium pellet (99.99%), and tellurium lump (99.99%) in a stoichiometric molar ratio of 3:1:2, prepared in an Ar-filled glove box. Subsequently, the mixture and an amount of the transport agent iodine were sealed together into an evacuated quartz tube. The sealed quartz tube was then placed in a two-zone tubular furnace. The temperatures were ramped to 1023/923 K over six hours, maintained for one week, and then cooled to room temperature naturally. Finally, high-quality FGT single crystals with a smooth surface and metallic luster were obtained.

Device fabrication and transport measurement
Pre-patterned Hall bars were fabricated using ultraviolet lithography (Aligner Suss, MABA6) and electron-beam deposition (LAB18) of Cr/Au (5/20 nm) on a 300-nm-thick SiO2/Si substrate. The high-quality vdW bulk single-crystal CrSBr and FGT were mechanically exfoliated into few-layer flakes inside an Ar-filled glove box. The transport was measured in the PPMS-9T (Quantum Design) system. The anomalous Hall effect and magnetoresistance measurements were performed using a Keithley Model 2400C source meter in conjunction with a Keithley Model 2612B nanovoltmeter. The devices were annealed at 393 K in an Ar-filled glove box to eliminate potential air gaps and ensure secure contact between the flakes.

Raman scattering and PL measurement
Raman spectroscopy and PL spectroscopy were carried out on the LabRam HR Evolution laser Raman spectrometer produced by the French JY company. The continuous laser of 532 nm was employed for the Raman and PL measurements; a 50× objective lens was used to focus the laser beam onto the sample surface, achieving a spot size of approximately 1 μm. The beam power was kept below 2 mW to avoid damaging the sample. For the measurement, we used a 30 s integration time and averaged a total of 10 spectra to increase the signal-to-noise ratio, and subtracted a background spectrum taken on the SiO2/Si substrate under the same conditions. During the assembly of the heterostructure, we designed the configuration to simultaneously obtain pristine CrSBr, pristine FGT, and CrSBr/FGT regions within a single sample, at each temperature point, measurements are taken separately on these three regions to acquire a complete set of temperature-dependent data. The sample was housed in a closed-cycle cryostat, and the Linkam THMS600 and liquid nitrogen were used for cooling the sample for a variable temperature test with 80 K–370 K.

Structural and magnetic measurements
The X-ray diffraction (XRD) patterns of CrSBr and FGT were obtained by using a Multifunctional Rotating-anode X-ray Diffractometer with Cu-Kα radiation (λ = 1.54178 Å). The Scanning Electron Microscope (SEM) images and Energy Dispersive Spectroscopy (EDS) mapping were captured by Gemini SEM 500. The atomic force microscope (AFM) images and Kelvin-probe force microscopy (KPFM) measurements were taken with a Dimension Icon Atomic Force Microscope produced by Bruker Nano Inc. in tapping mode. The magnetic properties were measured by a commercial superconducting quantum interference device (SQUID) magnetometer from Quantum Design. The XPEEM measurements were conducted at the MAXPEEM beamline of the MAX Ⅳ Laboratory (normal incidence of X-ray) and the I06 beamline at Diamond Light Source (16° incidence of X-ray). Fe and Cr XMCD-PEEM raw images were recorded by 1 s exposure time with right (R) and left (L) circularly polarized light at Fe L3 resonance at 707.3 eV and Cr L3 resonance at 576.4 eV. The XMCD asymmetry is given by (IL - IR)/(IL + IR). Cr XMLD-PEEM raw images were recorded by 5 s exposure time with linear horizontal (LH) and vertical (LV) polarized light at 575.4 eV, and the XMLD asymmetry is given by (ILH - ILV)/(ILH + ILV). The UPS data were collected at the ARPES beamline (BL13U) of the National Synchrotron Radiation Laboratory (NSRL, China), with a DA30 analyzer and 91.5 eV photon energy.

Micromagnetic simulations
For the micromagnetic simulations performed in MuMax3, we used a cell size of 2 nm × 2 nm × 1 nm and a total mesh of 512 × 512 × 4 cells (corresponding to 2 layers of FGT and 2 layers of CrSBr). Procedure for micromagnetic parameter extraction: first, the interlayer coupling in the heterostructure is turned off (i.e., FGT and CrSBr are treated as independent regions), after which the anisotropy and exchange energies are extracted for each layer. Then, the interlayer coupling is enabled, and the anisotropy and exchange energies are re-evaluated for comparison. The exchange stiffness of Aex for FGT and CrSBr were set to 6 pJ/m and 8 pJ/m, respectively, and the saturation magnetizations of Ms were set to 2.4 × 10^5 A/m and 1.67 × 10^5 A/m, respectively. The Gilbert damping constants α were chosen as 0.02 for FGT and 0.1 for CrSBr. The uniaxial anisotropy constant of FGT was set to 4.8 × 10^5 J/m^3, with the easy axis along the z-direction (out-of-plane), whereas that of CrSBr was set to 1.27 × 10^5 J/m^3, with the easy axis along the y-direction (in-plane). All simulated magnetic states were obtained by relaxing from a random initial spin configuration to reach equilibrium.

Theoretical calculations
First-principles calculations were performed using spin-polarized density functional theory (DFT) as implemented in the Quantum Espresso package. The electron-ion interactions were treated with the projected augmented wave (PAW) method, and the exchange-correlation effects were described using the generalized gradient approximation (GGA) in the Perdew-Burke-Ernzerhof (PBE) form. A plane-wave kinetic energy cutoff of 85 Ry was employed. The Hubbard-U correction was applied with an effective U value (Ueff) of 1.0 eV for Fe atoms and ±5.0 eV for Cr atoms. Van der Waals interactions were accounted for using the DFT-D3 scheme. The Brillouin zone was sampled with a 7 × 3 × 1 k-point mesh. Convergence thresholds were set to 10^-7 eV per atom for the self-consistent field iterations and 0.1 eV Å^-1 for atomic forces during structural relaxation. LBFGS algorithm was used to perform structural optimizations and cell relaxations.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The authors report measurements of the PL spectrum of CrSBr/Fe3GaTe2 heterostructures. They observe a strong dependence of the temperature and a steep rise of the main PL peak when moving below the Neel temperature of CrSBr in CrSBr/FGT heterostructures. The results are interpreted in terms of coupling to magnons and phonons. I find the results rather interesting and all experimental data appears to be of high quality. However, I am far from convinced on the general interpretation of the results and cannot recommend the manuscript for publication in Nat. comm.\nThe authors mention several times that charge transfer occurs between the FGT and CrSBr. Why is that not enough to explain the spin hardening and change in PL spectrum? There is a clear (but) weak coupling between the exciton energies and the magnetic order. But to refer to this as exciton magnon coupling is stretching it in my opinion. The excitons live at completely different energy scales compared to the magnons. Demonstrating dependence of PL on magnetic order is not the same as demonstrating exciton-magnon coupling. Along the same lines: the spin hardening could again be described by charge transfer right? So I cannot see that it is signalling interlayer magnetic interactions. Finally, the phonons are observed to depend on the magnetic order as well. In this case it is perhaps expected to have some degree of magnon-phonon coupling, but I cannot see any explicit evidence of it.\nTo summarize, I find the results of the manuscript interesting, but not the interpretation and title. The title is difficult to understans for one thing and I do not find any evidence of its claim. What does coherent magnon-exciton coupling mean? Why do you believe this coupling is mediated by phonons? And why do you believe it is boosted by spin-hardening?", "reviewer_2": "Excitons are of both fundamental interest and technological importance, showing great potential for applications in photospintronic and quantum technologies. In this manuscript, the authors investigate coherent exciton manipulation in a 2D CrSBr/Fe GaTe heterostructure by utilizing phonon-mediated magnon-exciton interactions. Through a series of comparative experiments, including temperature-dependent Raman/PL, Hall effect, and XPEEM techniques, they demonstrate that interfacial magnetic coupling and orbital-driven charge transfer induce reciprocal spin hardening. This further leads to phonon-constrained magnon dynamics and a corresponding anomalous increase in exciton energy. These findings hold significant importance for exciton physics and spintronics, which provide a promising approach for modulating excitonic properties in 2D AFM semiconductors and can advance the development of spin-based quantum photonic devices.\nI believe this work is interesting and suitable for publication in Nature Communications after addressing several concerns:\n1. In transport measurements, the FGT/CrSBr heterostructure is regarded as an electrically integrated system. However, it remains unclear whether the observed Hall response exclusively originates from the FGT layer. Given the pivotal role of interface effects in this study, it is important to deconvolute other potential contributions to the Hall signal in the heterostructure. Therefore, the possible influence of CrSBr may be considered. Clarifying this point is critical for a more accurate understanding of the magnetotransport mechanism in the system.\n2. Generally, within conventional FM/AFM heterostructures, exchange bias phenomena are frequently observed due to interfacial spin coupling. It would be informative for the authors to deliberate on whether any such effects exist in the CrSBr/FGT system. This consideration provides a valuable insight into the nature of the FM/AFM interface in this heterostructure.\n3. In Figure 3j, the author should explain why the vertical-axis values of the heterostructure do not align with those of the FGT reference in Figure 3i. Moreover, the magnitude of the anomalous Hall resistance in the heterostructure is significantly reduced compared to that of the pristine FGT layer, which also needs a mechanistic explanation for this discrepancy. These clarifications are beneficial to strengthen the interpretation of interlayer interactions and their influence on spin-dependent transport properties.\n4. It shows that although the long-range AFM order in CrSBr disappears around 130 K, certain magnetic and optical features persist beyond this temperature. Specifically, the enhanced coercive field in the heterostructure and the increased exciton energy splitting remain observable up to approximately 200 K. This apparent lagging behavior suggests the presence of underlying magnetic correlations or interfacial effects that endure above the Néel temperature. It is advisable for the authors to clarify the possible physical origins of these effects.\n5. In Fig. 4i and Fig. S18, the authors should give a detailed discussion on why the XMCD-PEEM images show no discernible signal, and the XMLD-PEEM images reveal a single domain. Additionally, more detailed configuration information should be included in the Methods section regarding how the XMCD and XMLD images were acquired and analyzed.\n6. A minor question. It is suggested that error bars should be added in Fig. 3e, 3f, 3k, and 3l to more precisely present the evolution process of the magnetic and magnetotransport properties as the temperature varies.\n7. While the paper is highly readable, there are still a few spelling issues. The abbreviation “XMCD-XPEEM” should be corrected to “XMCD-PEEM”. The term “flipping” should be more accurately expressed as “flopping” to more appropriately describe the gradual reorientation or tilting of spins under external fields or internal interactions.\nIn summary, I consider that the paper is interesting and has important guiding implications for the fields of spintronics and optoelectronics, but some minor revisions should be made to clarify the mentioned ambiguities and to meet the quality standards of NC.", "reviewer_3": "Lan et al present an experimental paper on the excitons of CrSBr layered on Fe3GaTe2. They find evidence of phonon coupling to magnetic order, exciton energy shifts with layering, and many other modifications to the CrSBr excitonic behavior. While their experiments are of high quality and contain careful analysis, I have a concern that their claims of tunability are somewhat overstated. Reading the abstract and conclusion, one would expect that they have found a way to control exciton energy over a wide range of energies--when in reality the shift is quite modest.\nI have very few technical comments on the manuscript as I am not an expert in them, but I do have the following recommendations:\n1. Fig 1, subpanel f: it would help readers if the red and green dashed lines were labeled on the figure rather than in the caption. Red and green are difficult to distinguish for colorblind readers, but a small label next to each line would help.\n2. Figure 2(a,b): The most noticeable feature in the temperature dependence of the photon energy is a big kink near 250K in CrSBr and at 200K in CrSBr/FGT. To my untrained eye, this is more noticeable than the kink at 130K. What is it? This needs to be commented upon, but it is not discussed.\n3. Line 345: What does \"at the momentum vector\" mean? Which momentum vector? The vector where phonons and magnons hybridize? If so, state that explicitly.\n4. Conclusion: \"The photon energy of CrSBr exhibits selective tunability\". This seems rather an exaggeration, as Fig. 2 shows that temperature shifts the exciton energy much more than layering. Indeed, the effect of layering is fairly minor, on the single meV level, whereas temperature has a 50 meV effect. Just so casual readers don't get the wrong idea, please explicitly state the percent \"tunability\" that layering produces in the CrSBr exciton. I am also quite skeptical of some of the other claims that e.g. this will be useful for dynamic tuning of laser output wavelengths. Please tone down the conclusion to realistic claims, or else back up those that seem fantastical.\nIn conclusion, I find the experimental results valid and worth publishing, but the discussion of applications seems decoupled from the actual magnitude of the effects measured. Perhaps I am ignorant of these applications, and a 6 meV shift at 100 K is really something new which will enable a technological breakthrough in photospintronics. But the reader needs more convincing. Whether this constitutes a significant enough advance for Nature Communications, I leave as a decision for the editor."}, "author_response": "Response to Reviewers and a Summary of Changes\nMany thanks to the reviewers for having given us valuable comments on the manuscript\n(NCOMMS-25-47700-T) submitted to Nature Communications.\nTitle: Spin hardening-boosted coherent magnon-exciton coupling via phonon-mediated\ntripartite interactions in van der Waals heterostructure\nAuthors: Weican Lan, Chaocheng Liu, Ruiqi Liu, Yafei Chu, Lu Cheng, Yajuan Feng,\nChao Wang, Huijuan Wang, Minghui Fan, Yuran Niu, Hengli Duan, Wensheng Yan\nWe deeply appreciate the valuable feedback and comments provided by the reviewers,\nas well as being grateful for their positive comments on this work: “I find the results\nrather interesting and all experimental data appears to be of high quality” (Reviewer\n#1); “These findings hold significant importance for exciton physics and spintronics”,\n“I believe this work is interesting and suitable for publication in Nature\nCommunications” (Reviewer #2); “Their experiments are of high quality and contain\ncareful analysis”, “I find the experimental results valid and worth publishing”\n(Reviewer #3).\nThe reviewers presented professional comments and revision suggestions before the\npaper could be reconsidered for publication in Nature Communications. Their insights\nhave been invaluable in guiding us towards enhancing the quality and clarity of our\nmanuscript. We have seriously considered these suggestions and comments, made the\nrevision accordingly, and would like to resubmit the revised manuscript. We sincerely\nappreciate the hard work of the reviewers and hope that the revised manuscript can meet\nthe acceptance criteria. The detailed responses to the comments are presented in a point-\nto-point manner as follows. Accordingly, all responses to reviewers' comments are\nhighlighted in blue; all revisions in the manuscript and supplementary files are\nhighlighted in red.\n------------------------------------\nResponse to Reviewer #1\n------------------------------------\nThe authors report measurements of the PL spectrum of CrSBr/Fe GaTe\n3 2\nheterostructures. They observe a strong dependence of the temperature and a steep rise\nof the main PL peak when moving below the Neel temperature of CrSBr in CrSBr/FGT\nheterostructures. The results are interpreted in terms of coupling to magnons and\nphonons. I find the results rather interesting and all experimental data appears to\nbe of high quality. However, I am far from convinced on the general interpretation of\nthe results and cannot recommend the manuscript for publication in Nat. Commun.\nWe sincerely appreciate the reviewer’s careful attention to our results and the\nrecognition of our experimental data quality. We fully understand the reviewer’s\nconcerns about our overall interpretation. In response, we have carefully revised the\nmanuscript, supplemented relevant evidence, and performed more in-depth analyses to\nsupport the coupling between magnons, excitons, and phonons. We believe these\nrevisions have significantly enhanced the clarity and reliability of our conclusions. We\nhope the revised manuscript now meets the high standards of Nature Communications,\nand thank the reviewer once again for your valuable feedback.\nComment: The authors mention several times that charge transfer occurs between the\nFGT and CrSBr. Why is that not enough to explain the spin hardening and change in\nPL spectrum? There is a clear (but) weak coupling between the exciton energies and\nthe magnetic order. But to refer to this as exciton magnon coupling is stretching it in\nmy opinion. The excitons live at completely different energy scales compared to the\nmagnons. Demonstrating dependence of PL on magnetic order is not the same as\ndemonstrating exciton-magnon coupling. Along the same lines: the spin hardening\ncould again be described by charge transfer right? So I cannot see that it is signalling\ninterlayer magnetic interactions. Finally, the phonons are observed to depend on the\nmagnetic order as well. In this case it is perhaps expected to have some degree of\nmagnon-phonon coupling, but I cannot see any explicit evidence of it.\nResponse: Thanks for your professional and valuable comments. In our constructed\nCrSBr/FGT heterostructure (semiconductor CrSBr/metal FGT), charge transfer persists\nacross the entire temperature range. However, a significant PL peak shift in CrSBr is\nonly observed below its T (the magnetic ordering temperature of CrSBr). When the\nN\ntemperature exceeds T , the CrSBr PL exhibits the same temperature-dependent\nN\nbehavior as pristine CrSBr, without any abrupt transition in PL peaks. Therefore, it is\nclearly evident that charge-transfer-driven effects are insufficient to explain the\nobserved spin hardening and exciton changes in CrSBr. Instead, the PL peak shift in\nCrSBr exhibits a close correlation with magnetic order under the effect of ferromagnetic\nsubstrate FGT. To further validate this conclusion, we conducted a comparative\nexperiment. We fabricated a heterostructure by stacking the nonmagnetic metallic\nmaterial WTe (whose conductivity is comparable to that of FGT [Nature 514, 205-208\n2\n(2014);Chin. Phys. Lett. 40, 087501 (2023)]) with CrSBr. The KPFM results (Fig. R1a)\ndemonstrated that charge transfer still occurs between the two materials in the same\ndirection. However, in the absence of interfacial magnetic interactions, the PL spectra\nexhibit no correlation with the magnetic order of CrSBr (Figs. R1b and R1c). This\nfurther confirms that the exciton changes in CrSBr cannot be fully explained by charge\ntransfer alone, but are primarily attributed to its magnon-exciton coupling modulated\nby FM FGT.\nThe intimate correlation manifested between excitons and magnons is generally\nreferred to as the coupling effect.Magnons, the quantized excitations of collective spin\nwaves, appear only in systems with long-range spin order (i.e., below the magnetic\ntransition temperature). Notably, this spin-order-dependent magnon–exciton interaction\nis macroscopically manifested as a significant dependence of excitonic energy on\nmagnetic order, which has been widely reported in numerous pioneering works,\nencompassing both single systems and heterostructures [Nature 609, 282-286 (2022);\nNat. Mater. 20, 1657-1662 (2021); Nature 583, 785-789 (2020); Nano Lett. 20, 4625-\n4630 (2020); Adv. Mater. 35, 2300247 (2023)]. In this context, excitons and magnons\npossess intrinsic coherence, termed magnon-exciton coupling. We certainly agree with\nyour viewpoint that excitons and magnons typically occupy distinct energy regimes.\nNotably, Xiaodong Xu and Xiaoyang Zhu et al. explicitly state in their Nature article:\n\"Although magnons and excitons are energetically mismatched by orders of magnitude,\ntheir coupling can lead to efficient optical access to spin information\" [Nature 609,\n282-286 (2022)], and they concurrently elucidate coherent magnon-exciton coupling\nbehavior in CrSBr. Undoubtedly, magnons and excitons can undergo coupling\ninteractions, leading to spin order/magnon-dependent excitonic energy shift. Such\nmagnon-exciton coupling behavior, manifesting as the dependence of PL on magnetic\norder, has been extensively verified in CrSBr [Nature 620, 533-537 (2023); Nat. Mater.\n20, 1657-1662 (2021); Nat. Nanotechnol. 18, 23-28 (2023); Nat. Mater. 24, 391-398\n(2025)]. On the other hand, regarding the role of charge transfer you are concerned\nabout, we do not completely rule out its influence on the PL peak shift. The charge\ntransfer occurring in CrSBr/FGT heterostructure cannot adequately account for this\nmagnon-exciton coupling behavior, yet it does play a pivotal role in mediating the\nanomalous excitonic PL peak shift. The charge transfer promotes interfacial magnetic\ninteractions, leading to spin hardening and phonon vibration confinement.\nConsequently, as we discussed in the main text, this process breaks the magnon-exciton\ncoupling constraints in CrSBr under the first-order perturbation theory (FPT),\nultimately inducing a blueshift in exciton energies. Therefore, we firmly believe that\nthe observed spin-order-dependent PL peak shift in the CrSBr/FGT heterostructure is\npredominantly governed by magnon-exciton coupling, with charge transfer providing\nsynergistic enhancement. More critically, we further perform a fitting analysis of the\nexciton peak shift in CrSBr using the power-law dependence of the AFM transition and\nyield a well-fitted result (Fig. R2), which further provides compelling evidence for\ncoherent magnon-exciton coupling in the heterostructure.\nSimilarly, we also acknowledge the fact that charge transfer contributes to spin\nhardening. We have claimed in the main text that orbital-mediated charge transfer\nassists in not only orientationally enhancing the spin ordering (spin hardening) in CrSBr\nbut also reciprocally amplifying the magnetization of FGT. However, despite the\npresence of charge transfer effects, interfacial magnetic interactions remain the\ndominant mechanism governing spin hardening. Specifically, the increased electron\noccupancy in Cr-3d orbitals of CrSBr enhances their electron cloud density and\namplifies the spatial overlap of adjacent Cr atomic orbitals [J. Am. Chem. Soc. 146,\n34070-34079 (2024); ACS Nano 17, 22684-22690 (2023); Nat. Commun. 16, 3691\n(2025)]. As a result, the strengthened orbital hybridization and Cr-Cr AFM coupling\nfurther stabilize the AFM spins along the zigzag chains and enhance the magnetic\nproximity interactions between CrSBr and FGT, collectively contributing to the spin\nhardening. Consequently, we conclude that the spin hardening in CrSBr results from\ninterfacial magnetic interactions, with a contribution from charge transfer. Actually, we\nhave presented sufficient analysis and results to demonstrate the interfacial magnetic\ninteractions in CrSBr/FGT heterostructure. For instance: the dependence of Raman\nmodes and PL peaks on magnetic order (Fig. 2); the enhanced spin-flop fields and\ncoercive fields observed in magnetotransport and Hall measurements (Fig. 3); and the\ncharacterization using synchrotron-based XAS and XPEEM (Fig. 4). Therefore, the\ninterfacial magnetic interactions definitely exist in our CrSBr/FGT heterostructure,\nevidencing their universal presence across all van der Waals magnetic heterostructures\n[Nat. Mater. 22, 305-310 (2023); Nat. Mater. 23, 212-218 (2024); Nat. Commun. 11,\n6021 (2020); Nat. Commun. 14, 2190 (2023); Nat. Nanotechnol. 16, 856-868 (2021);\nAdv. Mater. 37, 2413438 (2024); Nat. Mater. 22, 1311-1316 (2023)].\nAs you mentioned, the Raman modes of CrSBr also exhibit a close dependence on\nmagnetic order. In the CrSBr/FGT heterostructure, the A mode of CrSBr is strongly\n2g\nsuppressed below its T . However, when CrSBr enters a paramagnetic state above T ,\nN N\nthe A mode approximately aligns with that of pristine CrSBr. This result directly\n2g\ndemonstrates that magnetic exchange interaction between AFM CrSBr and FM FGT\nonly occurs below T . Consequently, due to the interfacial magnetic interaction\nN\nbetween the FGT and CrSBr, the Raman mode changes in CrSBr present a magnetic-\norder dependence. This signature feature is widely recognized as spin-phonon coupling,\nas generally reported in numerous pioneering studies, including in the CrSBr system\n[Sci. Adv. 7, eabj3106 (2021); Nat. Commun. 10, 345 (2019); Phys. Rev. B 107, 075421\n(2023)]. Furthermore, to more intuitively visualize the magnetic-order-dependent\nphonon mode variation, we further perform a fitting analysis of the A mode in CrSBr\n2g\nwithin the heterostructure. The acquired results demonstrate that its evolution follows\nAFM transition power-law behavior (Fig. R3), providing compelling explicit evidence\nfor spin-phonon coupling in our CrSBr/FGT heterostructure.\nOverall, we have ruled out the charge transfer as the sole factor governing spin\nhardening and PL spectral changes, establishing robust evidence for interfacial\nmagnetic interactions in the CrSBr/FGT heterostructure. We have demonstrated the\nexistence of both magnon-exciton coupling and spin-phonon coupling, and identified\nthat phonon-mediated magnon-exciton coupling in CrSBr is the fundamental origin of\nthe anomalous PL blueshift. Once again, we sincerely appreciate your thorough review\nand constructive comments, which greatly contributed to the improvement of our paper.\na b\n~ -42.1 meV\nCrSBr\nWTe 2\n~ -11.8 meV\nc\n1.3 1.4\nFig. R1.KPFM and temperature-dependent PL for CrSBr/WTe .a, KPFM topography and\n2\nwork function plots of CrSBr/WTe heterostructures. The blue and purple dashed lines mark\n2\nthe areas of CrSBr and WTe , respectively. Scale bar, 5 µm. b, Temperature-dependent PL\n2\nspectra for pristine CrSBr and CrSBr/WTe . The triangles correspond to the energy position of\n2\ntheir PL peaks.c, Variations of the PL peak positions for pristine CrSBr and CrSBr/WTe under\n2\ndifferent temperatures.\n).u.a(\nytisnetni\nLP\nCrSBr\n▼▼ CrSBr/WTe 2\n▼▼ 350 K\n▼▼ 300 K\n▼▼ 250 K\n▼▼ 220 K\n▼▼\n▼▼\n▼▼ 160 K\n▼▼\n▼▼ 120 K\n1.32\n▼▼\n▼▼\n1.30 ▼▼ 90 K\n100 150 200 250 300 350\nPhoton energy (eV)\n)Ve(\nygrene\nkaeP\nCrSBr\nCrSBr/WTe 2\nTemperature (K)\n1.36\n1.35\n1.34\n1.33\n1.32\n1.31\n1.30\n80 120 160 200 240\nFig. R2. Magnetic-order-dependent exciton fitting. Variations of the PL peak positions for\nCrSBr/FGT under different temperatures. The red solid curve is a best fit to the power law\nfunction .\n2\n2𝜔 𝛽\n𝐼 ∝[𝑎+𝑏(𝑇−𝑇𝑁) ]\nFig. R3.Magnetic-order-dependent phonon fitting. The intensity variation of A2 modes for\ng\nCrSBr/FGT under different temperatures. The red solid curve is a best fit to the power law\nfunction .\n2\n2𝜔 𝛽\n𝐼 ∝[𝑎+𝑏(𝑇−𝑇𝑁) ]\nRevision:\nAccordingly, Figs. R1-R3 with relevant captions have been added on pages 6, 8, 12\nof the Supplementary Materials.\nThe supplementary description “More critically, we perform a fitting analysis of\nexciton peak shift using the power-law[45] dependence of the AFM transition and yield\na well-fitted result (Fig. S5), which further provides compelling evidence for coherent\nmagnon-exciton coupling in the heterostructure.”; “To clarify the specific role of\ncharge transfer in this process,”; “Furthermore, we fabricated a heterostructure by\nstacking the nonmagnetic metallic material WTe (whose conductivity is comparable to\n2\nthat of FGT[46,47]) with CrSBr. The KPFM results (Fig. S7a) demonstrated that charge\ntransfer still occurs between the two materials in the same direction. However, in the\nabsence of interfacial magnetic interactions, the PL spectra (Figs. S7b and S7c) exhibit\n)Ve(\nygrene\nkaeP\nPL\nTemperature (K)\n80 120 160 200 240\n).u.a(\nytisnetni\nnamaR\nRM\nTemperature (K)\nno correlation with the magnetic order of CrSBr. This further confirms that the exciton\nchanges in CrSBr cannot be fully explained by charge transfer alone, but are primarily\nattributed to magnon-exciton coupling.” have been added at different positions on\npage 6 of the Main Text.\nThe supplementary description“We further perform a fitting analysis of the A2 mode\ng\nin CrSBr within the heterostructure. The acquired results demonstrate that its evolution\nfollows AFM transition power-law behavior (Fig. S11), providing compelling explicit\nevidence for spin-phonon coupling in our CrSBr/FGT heterostructure.” has been\nadded on page 7 of the Main Text.\nTo summarize, I find the results of the manuscript interesting, but not the\ninterpretation and title. The title is difficult to understans for one thing and I do not find\nany evidence of its claim. What does coherent magnon-exciton coupling mean? Why\ndo you believe this coupling is mediated by phonons? And why do you believe it is\nboosted by spin-hardening?\nResponse: We sincerely appreciate your efforts and dedication to our article, as well as\nbeing grateful for your comments on this work. We deeply apologize for any difficulties\nor confusion that our current manuscript may have caused. To address this, we have\nprovided further clarification regarding our experimental findings and the discussion of\nour results.\nIn our work, we demonstrate a reciprocal interfacial magnetic interaction within the\nCrSBr/FGT heterostructure, where the excitonic PL peaks of CrSBr exhibit a close\ndependence on magnetic order. In particular, we observe an anomalous blueshift in the\nPL peaks, which we verify to arise from phonon-mediated coherent magnon-exciton\ncoupling. Here, \"coherent magnon-exciton coupling\" refers to a specific quantum\nphenomenon where magnons (collective excitations of electron spins in magnetic\nmaterials) and excitons (bound electron-hole pairs in semiconductors) interact in a\nsynchronized, energy-exchanging manner [Nature 583, 785-789 (2020); Nature 609,\n282-286 (2022); Nat. Nanotechnol. 18, 23-28 (2023); Nat. Phys. 20, 801-806 (2024)].\nCoherent coupling is a strong, resonant interaction where energy oscillates back and\nforth between magnons and excitons. It requires matching frequency scales and spatial\noverlap, and results in hybrid states with new quantum properties [Nat. Phys. 17, 1137-\n1143 (2021); Phys. Rev. Lett. 125, 267201 (2020); Science 379, 278-283 (2023)].\nNotably, the characteristic dependence of exciton PL on magnetic order is commonly\ntermed coherent magnon-exciton coupling, as widely investigated in numerous seminal\nworks.\nRegarding the involvement of phonons in such magnon-exciton coupling, we have\nalso conducted an in-depth and meticulous analysis. Based on the magnetic-order-\ndependent changes in phonon modes, we identified the existence of spin-phonon\ncoupling in the CrSBr/FGT heterostructure. Moreover, this coupling effect constrains\nthe phonon vibrations of magnetic atoms in CrSBr. As established, phonons can\nenhance magnon transport and propagation via magnon-phonon hybridization [Sci. Adv.\n7, eabj3106 (2017); Proc. Natl. Acad. Sci. USA 112, 8977-8981 (2015)]. We therefore\nconclude that phonons can participate in the interaction between magnons and excitons.\nAccording to conventional FPT constrain, excitonic PL shift typically occurs only\ntowards lower energies. However, in our system, apart from the restricted phonon\nvibrations in CrSBr, there are no other potential factors that could account for the\nanomalous blueshift of excitonic PL. Consequently, based on the comprehensive\ndiscussion and analysis above, the anomalous PL blueshift induced by magnon-exciton\ncoupling can be primarily attributed to the phonon-mediated influence, which is\ntheoretically/experimentally supported and permissible [Phys. Rev. B 108, 144425\n(2023); J. Phys. D: Appl. Phys. 51, 224008 (2018); Nano Lett. 23, 9235-9242 (2023);\nNat. Commun. 14, 1047 (2023); Nat. Commun. 14, 88 (2023)]. Moreover, we also\nperform the AFM transition correlated power-law fitting for CrSBr phonons (Fig. R3)\nand identify the spin-phonon coupling in the heterostructure, further highlighting the\nmediating influence of phonons on the magnon-exciton coupling. Therefore, we have\ncompelling grounds to conclude that phonons are engaged in the magnon-exciton\ncoupling, ultimately giving rise to the anomalous blueshift of PL peaks.\nThrough systematic characterization and analysis using magnetic, electrical, and\nspectroscopic techniques (Figs. 3 and 4), we confirm that the spins of CrSBr and FGT\nare both orientationally enhanced (spin-hardening) with significantly elevated spin-flop\nfields and coercive fields. We further unveil a positive correlation between spin-\nhardening and PL peak shift (see supplementary Fig. S15), confirming that higher spin\nhardening leads to a larger PL peak shift. This thus signifies that enhanced spin\nhardening will induce stronger magnon-exciton coupling, i.e., spin hardening-boosted\nmagnon-exciton coupling. More precisely, the complete physical picture of magnon-\nexciton-phonon tripartite interactions in CrSBr is that charge transfer and interfacial\nmagnetic interactions lead to spin-hardening and constrained phonon vibrations. These\nhardened spins simultaneously undergo magnon-exciton coupling while being\ninfluenced by vibrationally restricted phonons (via spin-phonon coupling), thereby\nresulting in an anomalous energy shift of the excitons.\nIn summary, based on the magnetic-order-dependent characteristic changes in\nRaman modes and excitonic PL, we confirm the presence of both spin-phonon coupling\nand magnon-exciton coupling in CrSBr, which are modulated by FM FGT. These\nconclusions are further substantiated by the power-law fitting of the AFM transition.\nBy revealing and analyzing the positive correlation between spin-hardening and spin-\nflop, we establish that hardened spins promote magnon-exciton coupling in CrSBr.\nMoreover, through systematic analysis, we further confirm that phonons mediate this\nmagnon-exciton coupling process, resulting in the emergence of an anomalous PL peak\nblueshift in CrSBr. Once again, we are grateful for your professional comments and\nenthusiastic dedication, which have greatly helped us improve our manuscript.\n------------------------------------\nResponse to Reviewer #2\n------------------------------------\nExcitons are of both fundamental interest and technological importance, showing great\npotential for applications in photospintronic and quantum technologies. In this\nmanuscript, the authors investigate coherent exciton manipulation in a 2D\nCrSBr/Fe GaTe heterostructure by utilizing phonon-mediated magnon-exciton\n3 2\ninteractions. Through a series of comparative experiments, including temperature-\ndependent Raman/PL, Hall effect, and XPEEM techniques, they demonstrate that\ninterfacial magnetic coupling and orbital-driven charge transfer induce reciprocal spin\nhardening. This further leads to phonon-constrained magnon dynamics and a\ncorresponding anomalous increase in exciton energy. These findings hold significant\nimportance for exciton physics and spintronics, which provide a promising approach\nfor modulating excitonic properties in 2D AFM semiconductors and can advance the\ndevelopment of spin-based quantum photonic devices. I believe this work is\ninteresting and suitable for publication in Nature Communications after addressing\nseveral concerns:\nThank you for your thoughtful and constructive feedback on our manuscript. As you\nrightly highlighted, excitons can not only serve as a rich platform for fundamental\nresearch but also holdgreat potential for applications in opto-spintronics and quantum\ntechnologies. In this study, we designed a 2D CrSBr/Fe GaTe heterostructure to\n3 2\ninvestigate the coherent exciton modulation via phonon-mediated magnon-exciton\ninteractions. We believe our findings offer important insights into exciton physics,\nquantum photonic devices, and spintronics in 2D systems, providing a novel approach\nto modulate excitonic behavior in vdW AFM semiconductors. We are grateful for your\nrecognition of the innovation and significance of our work, and we will carefully\naddress all remaining concerns to ensure the manuscript meets the high standards of\nNature Communications. Below are our detailed responses to your comments.\nComment 1) In transport measurements, the FGT/CrSBr heterostructure is regarded as\nan electrically integrated system. However, it remains unclear whether the observed\nHall response exclusively originates from the FGT layer. Given the pivotal role of\ninterface effects in this study, it is important to deconvolute other potential contributions\nto the Hall signal in the heterostructure. Therefore, the possible influence of CrSBr may\nbe considered. Clarifying this point is critical for a more accurate understanding of the\nmagnetotransport mechanism in the system.\nResponse: We thank the reviewer for this insightful comment. To exclude the possible\ncontribution from CrSBr to the Hall response in the heterostructure, we performed\ncontrol Hall measurements on devices consisting solely of CrSBr flakes, using the same\nelectrode configuration and measurement conditions (Fig. R4). The results show that\nCrSBr alone exhibits no measurable Hall signal within the noise level of our\nmeasurement system, which is consistent with its AFM semiconducting nature and its\nnegligible carrier density at low temperatures [Adv. Mater. 32, 2003240 (2020)].\nThese results confirm that the Hall response observed in the FGT/CrSBr\nheterostructure originates exclusively from the FGT layer. Therefore, the changes in the\nHall signal can be attributed to the interfacial magnetic coupling and spin modulation\ninduced by CrSBr, rather than to any direct transport contribution from CrSBr itself.\n15\n10\n5\n0\n−5\n−10\n−15\n−9 −6 −3 0 3 6 9\nFig. R4. Hall measurement of CrSBr. R of the pristine CrSBr versus magnetic field at 5 K,\nxy\nmeasured with a perpendicular applied magnetic field. The inset shows an optical image of the\nCrSBr device. Scale bar, 20 µm.\nRevision:\nAccordingly, Fig. R4 with the relevant caption has been added on page 18 of the\nSupplementary Materials.\nThe supplementary description “To clarify the signal origin, we independently\nmeasured the Hall response of CrSBr and found a negligible Hall resistance (Fig. S17),\ndemonstrating that the Hall signals observed in the heterostructure originate solely from\nthe FGT layer.” has been added on page 9 of the Main Text.\nComment 2) Generally, within conventional FM/AFM heterostructures, exchange bias\nphenomena are frequently observed due to interfacial spin coupling. It would be\ninformative for the authors to deliberate on whether any such effects exist in the\nCrSBr/FGT system. This consideration provides a valuable insight into the nature of\nthe FM/AFM interface in this heterostructure.\nResponse: We sincerely appreciate the reviewer for raising this insightful question\nregarding the possible emergence of exchange bias in the CrSBr/FGT heterostructure.\nExchange bias is a well-known interfacial phenomenon that typically arises in\nconventional ferromagnet/antiferromagnet (FM/AFM) heterostructures. It manifests as\n)Ωk(\nR\nyx\nx\nField (T)\na horizontal shift in the magnetic hysteresis loop and is commonly attributed to\nunidirectional anisotropy induced by interfacial exchange coupling between pinned\nAFM spins and switchable FM moments [Phys. Rev. 105, 904 (1957)]. The\nestablishment of exchange bias generally requires two key conditions: (1) strong\ninterfacial coupling between the FM and AFM layers, and (2) aligned or at least non-\northogonal magnetic anisotropies between the two components, which facilitates\ncoherent spin pinning across the interface [Nat. Commun. 14, 2190 (2023); Nano Lett.\n20, 5030 (2020); Adv. Mater. 32, 2002032 (2020)].\nIn our CrSBr/FGT heterostructure, although strong interfacial magnetic interactions\nare indeed present, evidenced by the observed spin hardening and phonon-constrained\nmagnon dynamics, the magnetic easy axes of the two constituents are nearly orthogonal.\nFGT exhibits out-of-plane magnetization, while CrSBr possesses a strong in-plane\nantiferromagnetic anisotropy (as shown in Figs. 1b, 1c of the manuscript). This\northogonal spin configuration is generally unfavorable for the formation of a stable\nunidirectional exchange field, thereby suppressing the conventional exchange bias\neffect.\nConsistent with this interpretation, our magnetization measurements (as shown in\nFigs. 3i, 3j of the manuscript) show no significant loop shift or coercivity asymmetry.\nNevertheless, we believe the distinct spin configuration at the CrSBr/FGT interface\noffers an alternative pathway for novel interfacial spin phenomena, such as spin\nhardening and coherent magnon-exciton coupling, which are not typically accessible in\nconventional FM/AFM systems.\nComment 3) In Figure 3j, the author should explain why the vertical-axis values of the\nheterostructure do not align with those of the FGT reference in Figure 3i. Moreover, the\nmagnitude of the anomalous Hall resistance in the heterostructure is significantly\nreduced compared to that of the pristine FGT layer, which also needs a mechanistic\nexplanation for this discrepancy. These clarifications are beneficial to strengthen the\ninterpretation of interlayer interactions and their influence on spin-dependent transport\nproperties.\nResponse: We appreciate the reviewer’s careful observation and insightful comment.\nThe difference in the vertical-axis values of the Hall resistance between the pristine\nFGT and the FGT/CrSBr heterostructure arises from the presence of the additional\nCrSBr layer. Since CrSBr is a semiconducting material with significantly higher\nresistivity compared to metallic FGT [Adv. Mater. 34, 2109759 (2022); Nat. Commun.\n13, 5067 (2022)], and it increases the overall resistance of the heterostructure when\nincorporated into the vertical device stack. The reduced magnitude of the anomalous\nHall resistance in the heterostructure can be attributed to the interlayer charge transfer\nfrom CrSBr to FGT. This charge transfer decreases the number of unpaired Fe 3d\nelectrons in the FGT layer (as shown in Fig. 4b of the manuscript), thereby reducing\nthe net magnetic moment and consequently weakening the anomalous Hall response.\nThis explains why the red curve (heterostructure) in Fig. 3l is consistently lower in\nmagnitude than the purple curve (pristine FGT). Nevertheless, this reduction in absolute\nHall resistance does not affect the characteristic changes associated with magnetic\ntransitions, which are governed by the interfacial magnetic coupling between CrSBr\nand FGT.\nComment 4) It shows that although the long-range AFM order in CrSBr disappears\naround 130 K, certain magnetic and optical features persist beyond this temperature.\nSpecifically, the enhanced coercive field in the heterostructure and the increased\nexciton energy splitting remain observable up to approximately 200 K. This apparent\nlagging behavior suggests the presence of underlying magnetic correlations or\ninterfacial effects that endure above the Néel temperature. It is advisable for the authors\nto clarify the possible physical origins of these effects.\nResponse: We appreciate the reviewer’s careful reading and valuable suggestions. To\nclarify, CrSBr is a typical layered A-type antiferromagnet with in-plane AFM ordering\n[J. Magn. Magn. Mater. 92, 129. (1990)]. Above its Néel temperature (~130 K), CrSBr\ndoes not immediately transition into a conventional paramagnetic state. Instead, it\nexperiences a narrow temperature range within which the long-range AFM order\nvanishes, while some residual short-range magnetic correlations still persist to some\ndegree. These residual short-range magnetic orders have been reported in previous\nstudies [Nat. Mater. 21, 754 (2022); Adv. Mater. 32, 2003240 (2020); Nano Lett. 21,\n3511 (2021)] and are understood as quasi-static magnetic features, which may cause\ncertain observable magnetic and optical responses even beyond the Néel temperature.\nIn our CrSBr/FGT heterostructure, although the system exhibits overall spin\nhardening, the strong magnetic exchange coupling at the interface with ferromagnetic\nFGT may induce localized ferromagnetic ordering or enhance magnetic correlations\nwithin CrSBr. This interfacial effect likely explains the persistent observation of the\nenhanced exciton energy and increased coercive field up to approximately 200 K. This\n“lagging” magnetic behavior suggests that interface-driven local magnetic order or\nresidual short-range correlations extend beyond CrSBr’s intrinsic magnetic transition\ntemperature, thereby maintaining certain magnetic and optical features above the Néel\ntemperature.\nRevision:\nAccordingly, the supplementary description “Within these temperature ranges,\nCrSBr/FGT exhibits even lower photon energies compared to pristine CrSBr, achieving\na maximum difference of around 200 K. This observation indicates that the excitonic\nresponse in the heterostructure remains sensitive to interfacial magnetic effects over an\nexpanded temperature range, far exceeding the T of CrSBr. This suggests that the\nN\nmagnetic proximity effect and residual short-range magnetic correlations[25,26,30]\ninduced by the FGT layer persist well above the intrinsic magnetic transition\ntemperature of CrSBr.” has been added on page 6 of the Main Text.\nComment 5) In Fig. 4i and Fig. S18, the authors should give a detailed discussion on\nwhy the XMCD-PEEM images show no discernible signal, and the XMLD-PEEM\nimages reveal a single domain. Additionally, more detailed configuration information\nshould be included in the Methods section regarding how the XMCD and XMLD\nimages were acquired and analyzed.\nResponse: Thanks for your professional comments. All XPEEM data were recorded on\nMAXPEEM beamline at MAX IV Lab, after cooling from room temperature to 100 K\nunder zero magnetic field with normal incidence (90) of X-ray on the sample surface.\nThis setup is sensitive to out-of-plane FM and in-plane AFM but cannot detect the in-\nplane FM domain. Fe and Cr XMCD-PEEM raw images were recorded by 1 s exposure\ntime with right (R) and left (L) circularly polarized light at Fe L resonance at 707.3 eV\n3\nand Cr L resonance at 576.4 eV. The XMCD asymmetry is given by\n3\n. Cr XMLD-PEEM raw images were recorded by 5 s exposure tim𝐿e wi𝑅th lin𝐿ear\n(𝐼 −𝐼 )/(𝐼 +\nh𝑅orizontal (LH) and vertical (LV) polarized light at 575.4 eV, and the XMLD\n𝐼 )\nasymmetry is given by . Therefore, the Cr XMCD-PEEM\nimage in Fig. S22 shows no𝐿 d𝐻iscer𝐿n𝑉ible c𝐿o𝐻ntras𝐿t,𝑉 which means there is no out-of-plane\n(𝐼 −𝐼 )/(𝐼 +𝐼 )\nFM moment for Cr element in FGT/CrSBr heterostructure. The Cr XMLD-PEEM\nimage in Fig. 4i shows dark contrast in CrSBr area, which means the b-axis orientation\nof the AFM moments in CrSBr. Meanwhile, we have switched the order of the original\nFig. 4i and Fig. S22 to improve the overall logical sequence of the manuscript. All these\nrevisions have been clearly highlighted in the revised manuscript.\nRevision:\nAccordingly, the relevant experimental parameters and conditions “All XPEEM data\nwere recorded after cooling from room temperature to 100 K under zero magnetic field\nwith normal incidence (90) of X-ray on the sample surface. This setup is sensitive to\nout-of-plane FM and in-plane AFM but cannot detect the in-plane FM domain.” have\nbeen thoroughly described on page 11 of the Main Text.\nThe supplementary description “The XPEEM measurement was carried out at the\nPEEM endstation of the MAXPEEM Beamline at the MAX IV laboratory (Lund,\nSweden). Fe and Cr XMCD-PEEM raw images were recorded by 1 s exposure time\nwith right (R) and left (L) circularly polarized light at Fe L resonance at 707.3 eV and\n3\n𝐿 𝑅 𝐿 𝑅\n(𝐼 −𝐼 )/(𝐼 +𝐼 )\nCr XMLD-PEEM raw images were recorded by 5 s exposure time with linear horizontal\n(LH) and vertical (LV) polarized light at 575.4 eV, and the XMLD asymmetry is given\nby ” has been added on page 19 of the Methods section in the\nMain 𝐿T𝐻ext. 𝐿𝑉 𝐿𝐻 𝐿𝑉\n(𝐼 −𝐼 )/(𝐼 +𝐼 )\nComment 6) A minor question. It is suggested that error bars should be added in Fig.\n3e, 3f, 3k, and 3l to more precisely present the evolution process of the magnetic and\nmagnetotransport properties as the temperature varies.\nResponse: We thank the reviewer for this insightful suggestion. We agree that error\nbars would help to more clearly illustrate the evolution of magnetic and\nmagnetotransport properties with temperature. Accordingly, we have added appropriate\nerror bars in Figs. 3e, 3f, 3k, and 3l in the revised manuscript to reflect measurement\nuncertainties and improve the clarity of data presentation. The corresponding figure\ncaption has also been updated on page 10 of the Main Text. We appreciate the\nreviewer’s attention to this detail.\ne f k l\n2.0\n1.5 T N T 1.0 N T N\n0.5\n0.0\n30 60 90 120 150\nFig. 3. e-f, The extracted H (e) and MRR (f) vary with temperature. k-l, The extracted H (k)\ns c\nand R (l) as a function of temperature.\nxy\nComment 7) While the paper is highly readable, there are still a few spelling issues.\nThe abbreviation “XMCD-XPEEM” should be corrected to “XMCD-PEEM”. The term\n“flipping” should be more accurately expressed as “flopping” to more appropriately\ndescribe the gradual reorientation or tilting of spins under external fields or internal\ninteractions.\nResponse: We sincerely thank the reviewer for their careful reading and constructive\nsuggestions regarding spelling and terminology. In response to the reviewer’s comment,\nwe have corrected the abbreviation “XMCD-XPEEM” to “XMCD-PEEM” throughout\nthe manuscript. The corrected term “XMCD-PEEM” more accurately refers to X-ray\nmagnetic circular dichroism measurements performed using photoemission electron\nmicroscopy, and reflects common usage in the field. Furthermore, we have revised the\nterm “flipping” to “flopping” in the context of spin dynamics. We agree that “flopping”\nmore accurately describes the gradual reorientation or canting of spins under external\nmagnetic fields or interfacial exchange coupling, especially in systems with AFM or\n)T( H s\nCrSBr 0 FGT/CrSBr\n−10\n−20\n−30\n60 120 180 240\nTemperature (K)\n)%( RRM\nCrSBr FGT/CrSBr\n0.6\n0.4\n0.2\n0.0\n0 50 100 150 200 250 300\nTemperature (K)\n)T( H c\nFGT CrSBr/FGT 0.36\n0.32\n0.28\n0.24\n0.20\n0.16\n0 50 100 150 200 250 300\nTemperature (K)\n)Ω( R yx\nFGT CrSBr/FGT\nTemperature (K)\ncanted spin structures. These refinements improve the scientific accuracy and clarity of\nour manuscript. In addition to the grammatical and typographical issues kindly pointed\nout by the reviewer, we have also carefully checked the manuscript and identified a few\nadditional inaccuracies and inconsistencies on our own. All revisions are highlighted in\nred in the revised manuscript. Thank you once again for your kind review and helpful\nsuggestions.\nIn summary, I consider that the paper is interesting and has important guiding\nimplications for the fields of spintronics and optoelectronics, but some minor\nrevisions should be made to clarify the mentioned ambiguities and to meet the quality\nstandards of NC.\nWe sincerely appreciate your high recognition of our work and deeply appreciate your efforts and\ndedication. Based on your professional comments and suggestions, we have carefully\nrevised our manuscript. We eagerly hope that the revised version can meet\nyour requirements and satisfy the acceptance criteria of NC.\n------------------------------------\nResponse to Reviewer #3\n------------------------------------\nLan et al present an experimental paper on the excitons of CrSBr layered on Fe GaTe .\n3 2\nThey find evidence of phonon coupling to magnetic order, exciton energy shifts with\nlayering, and many other modifications to the CrSBr excitonic behavior. While their\nexperiments are of high quality and contain careful analysis, I have a concern that\ntheir claims of tunability are somewhat overstated. Reading the abstract and conclusion,\none would expect that they have found a way to control exciton energy over a wide\nrange of energies--when in reality the shift is quite modest.\nWe would like to express our sincere gratitude to you for your insightful comments and\nsuggestions. Upon careful reconsideration, we recognize that certain statements in the\nabstract and conclusion may inadvertently overstate the extent of the observed energy\nshifts, potentially giving the impression of large-scale spectral modulation. Therefore,\nwe have revised the manuscript to clearly specify the extent of exciton energy\nmodulation and objectively analyze its promising potential. We clarify that although the\ntuning range is limited compared to external apparatus such as electric/magnetic\nfields, this approach offers a distinctive advantage: it enables fine control of exciton\nenergies without requiring external fields. We believe this constitutes a novel and\npotentially practical strategy for excitonic modulation, which could be valuable for\nfuture device applications. Once again, we sincerely appreciate the reviewer’s positive\nevaluation and constructive feedback.\nComment 1) Fig 1, subpanel f: it would help readers if the red and green dashed lines\nwere labeled on the figure rather than in the caption. Red and green are difficult to\ndistinguish for colorblind readers, but a small label next to each line would help.\nResponse: We thank the reviewer for the valuable suggestion regarding figure\naccessibility. In the revised version of Fig. 1f, we have added small text labels directly\nnext to the red and green dashed lines to improve clarity for all readers, including those\nwith color vision deficiency. We believe this adjustment enhances the readability and\naccessibility of the figure. The revised Fig. 1f has been updated on page 5 of the Main\nText.\nf\nCrSBr\n12 nm\n5 nm\nFGT\nFig. 1f. The optical micrograph and thickness line profile of FGT/CrSBr heterostructures on\nSiO /Si substrate. The red and green dashed lines sketch the areas of CrSBr and FGT,\n2\nrespectively. Scale bar, 10 µm.\nComment 2) Figure 2(a,b): The most noticeable feature in the temperature dependence\nof the photon energy is a big kink near 250K in CrSBr and at 200K in CrSBr/FGT. To\nmy untrained eye, this is more noticeable than the kink at 130K. What is it? This needs\nto be commented upon, but it is not discussed.\nResponse: We thank the reviewer for raising this insightful question. Here we provide\na separate discussion on the two anomalous temperature points mentioned by the\nreviewer:\n(1) “a big kink near 250K in CrSBr”. Although a certain degree of steepness can\nindeed be observed near 250 K in Fig. 2a, we attribute this feature primarily to the\nrelatively large temperature intervals used during the measurement. Above 200 K, as\nthe CrSBr system enters a paramagnetic state, we increased the temperature step to 50 K\nfor the PL measurements. This wider interval leads to a less continuous data appearance\nand makes the exciton energy shift seem more abrupt. Nevertheless, the overall trend\nremains essentially linear within the margin of error. As shown in Fig. 2d, the evolution\nacross this temperature range is smooth, with no clear sign of a sudden transition.\n(2) “200K in CrSBr/FGT”. Indeed, as shown in Fig. 2(b,d,e), a pronounced kink can\nbe observed around 200 K in CrSBr/FGT heterostructure, with a magnitude even\ngreater than the change near the Néel temperature (~130 K). We have carefully\nanalyzed this issue and provide the following discussion:\nCrSBr is a prototypical layered A-type antiferromagnet, characterized by\nferromagnetic coupling within each layer and antiferromagnetic alignment between\nadjacent layers. Above its Néel temperature, the system does not immediately enter a\nfully paramagnetic state. Instead, it undergoes a narrow transitional regime (~10 K) in\nwhich long-range antiferromagnetic order is lost, while short-range interlayer\nferromagnetic correlations may persist. Prior studies [Nat. Mater. 21, 754 (2022); Adv.\nMater.32, 2003240 (2020);Nano Lett.21, 3511 (2021)] have reported such short-range\nmagnetic ordering, which often manifests as quasi-static magnetic features that remain\nobservable in both magnetic and optical responses, exhibiting a form of “magnetic\nmemory” or hysteresis.\nIn the CrSBr/FGT heterostructure, the strong intrinsic ferromagnetism of FGT may\ninduce or stabilize local ferromagnetic alignment within the CrSBr layer via interfacial\nexchange coupling, thereby extending the influence of short-range magnetic\ncorrelations. This effect may account for the abrupt shift in exciton energy observed\nnear 200 K—well above the intrinsic magnetic transition temperature of CrSBr. Such a\npronounced deviation suggests that interfacial magnetic interactions can significantly\ninfluence excitonic states over an expanded temperature range. The excitonic kink near\ndetectable optical response. Indeed, the behavior above the Néel temperature is more\nintricate. While our earlier analysis primarily focused on coupling features at low\ntemperatures, we acknowledge that the anomalous excitonic behavior above the\nmagnetic transition temperature was not sufficiently addressed in the original\nmanuscript. Corresponding discussions have now been added in the revised version.\nWe sincerely appreciate the reviewer’s insightful comment, which has drawn our\nattention to this important temperature regime and helped us improve the clarity and\ncompleteness of our analysis.\nRevision:\nAccordingly, the supplementary description “Within these temperature ranges,\nCrSBr/FGT exhibits even lower photon energies compared to pristine CrSBr, achieving\na maximum difference of around 200 K. This observation indicates that the excitonic\nresponse in the heterostructure remains sensitive to interfacial magnetic effects over an\nexpanded temperature range, far exceeding the T of CrSBr. This suggests that the\nN\nmagnetic proximity effect and residual short-range magnetic correlations[25,26,30]\ninduced by the FGT layer persist well above the intrinsic magnetic transition\ntemperature of CrSBr.” has been added on page 6 of the Main Text.\nComment 3) Line 345: What does \"at the momentum vector\" mean? Which momentum\nvector? The vector where phonons and magnons hybridize? If so, state that explicitly.\nResponse: We sincerely thank the reviewer for this thoughtful and important question.\nIndeed, in our original manuscript, the phrase “at the momentum vector” does not refer\nto an arbitrary momentum point, but rather to the specific point or narrow range in\nmomentum space where the intrinsic dispersion curves of phonons and magnons\nintersect or come very close to each other. At these points, the proximity of their\ndispersion relations leads to enhanced magneto-elastic coupling, which in turn induces\nstrong hybridization between the two excitations—forming the so-called resonant\nmagnetoelastic mode. This process effectively facilitates faster propagation of magnons\nin the low-momentum region [Phys. Rev. Lett.115, 197201 (2015);Phys. Rev. Lett.117,\n207203 (2016)]. We acknowledge that the original wording was imprecise and could\ncause confusion. Therefore, we have revised the manuscript to clarify this point\naccordinglyand have included relevant references for support.\nRevision:\nAccordingly, the original description on page 14 of the Main Text “Furthermore, the\npropagation of magnons at the momentum vector is related to the hybridization between\nmagnons and acoustic phonons through magneto-elastic coupling[53-54].” has been\nchanged to “Furthermore, the enhanced propagation of magnons arises at specific\nmomentum regions where the intrinsic dispersion relations of magnons and acoustic\nphonons intersect or come into close proximity, enabling strong hybridization through\nmagnetoelastic coupling[56-59].”\nComment 4) Conclusion: \"The photon energy of CrSBr exhibits selective tunability\".\nThis seems rather an exaggeration, as Fig. 2 shows that temperature shifts the exciton\nenergy much more than layering. Indeed, the effect of layering is fairly minor, on the\nsingle meV level, whereas temperature has a 50 meV effect. Just so casual readers don't\nget the wrong idea, please explicitly state the percent \"tunability\" that layering produces\nin the CrSBr exciton. I am also quite skeptical of some of the other claims that e.g. this\nwill be useful for dynamic tuning of laser output wavelengths. Please tone down the\nconclusion to realistic claims, or else back up those that seem fantastical.\nResponse: Thanks for your professional and valuable comments. In response to your\nconcern regarding the magnitude of exciton energy modulation, we provide the\nfollowing clarification:\nWe fully acknowledge that the exciton energy modulation achieved in our current\nexperiments is relatively limited—approximately 8 meV, which is smaller than the\ntemperature-induced exciton energy variation of up to 50 meV. However, it is worth\nnoting that such a substantial temperature-driven shift requires an extremely broad\ntemperature range (from 80 K to 350 K), which is inefficient for practical exciton\nenergy control. Moreover, the redshift of exciton energy induced by temperature\nthermal effects is a common phenomenon in most material systems and, strictly\nspeaking, cannot be regarded as control or modulation. In contrast, the layer-stacked\nCrSBr/FGT strategy presented in this work enables exciton energy modulation within\na narrow temperature window near the magnetic phase transition, without requiring\nlarge temperature variations. This strategy demonstrates more efficient and flexible\ncontrol capabilities in exciton energy through magnon-exciton coupling. On the other\nhand, to explicitly state the percent \"tunability\", we note that external magnetic field\ndevices can achieve a maximum exciton energy shift of approximately 20 meV [Nature\n609, 282-286 (2022); Nat. Mater. 20, 1657-1662 (2021)]. In this context, the 8 meV\nshift achieved in our work can reach 40% of the modulation amplitude achievable with\nexternal magnetic fields. This represents a considerable degree of modulation. More\nimportantly, our strategy does not require any external magnetic field or other complex\ninstrumentation, thereby offering new pathways and application potential for exciton\nmanipulation and utilization.\nTo avoid overstated claims in the original manuscript, we have revised the relevant\nexpressions in the manuscript. For example, phrases such as “selective tunability of the\nphoton energy in CrSBr” have been clarified to more accurately reflect the modulation\nmagnitude and underlying physical mechanisms. Similarly, forward-looking statements\nlike “this study can be used for dynamic tuning of laser emission wavelength” have\nbeen either moderated or removed, with additional qualifiers and contextual\nexplanations added to better reflect their realistic significance. We sincerely thank the\nreviewer for the constructive feedback, which has helped us improve the rigor and\naccuracy of our manuscript.\nRevision:\nAccordingly, the original description on page 2 of the Main Text “Our findings\nuncover an accessible avenue for the tunable modulation of exciton energy in 2D AFM\nsemiconductors, thus potentially addressing the demand for diverse wavelength light\nsources in quantum information and optoelectronic technology such as communication\nand sensing.” has been changed to“Our findings demonstrate an approach for modest\nmodulation of exciton energy in 2D AFM semiconductors, which may provide insights\nfor future exploration of wavelength control in quantum information and optoelectronic\ntechnologies such as communication and sensing.”.\nThe original description on page 15 of the Main Text “Notably, here the photon\nenergy of CrSBr exhibits selective tunability depending on magnon-exciton coupling,\nunveiling significant potential in achieving dynamic tuning of laser output wavelengths.”\nhas been changed to “Notably, the exciton energy shift achieved in our work can reach\n40% of the modulation amplitude achievable with external magnetic fields[32,35],\nindicating a substantial level of modulation and offering a valuable reference for future\nstudies on wavelength control in laser systems.”.\nIn conclusion, I find the experimental results valid and worth publishing, but the\ndiscussion of applications seems decoupled from the actual magnitude of the effects\nmeasured. Perhaps I am ignorant of these applications, and a 6 meV shift at 100 K is\nreally something new which will enable a technological breakthrough in\nphotospintronics. But the reader needs more convincing. Whether this constitutes a\nsignificant enough advance for Nature Communications, I leave as a decision for the\neditor.\nSincere thanks for your recognition of our work. We deeply appreciate your efforts and\ndedication to our article, as well as being grateful for your comments on this work. In\naccordance with your expert comments and suggestions, we have meticulously revised\nthe manuscript. We sincerely hope this revised version merits your approval and\nsatisfies the high standards of Nature Communications."}, {"round": 2, "reviewer_comments": {"reviewer_2": "The authors have addressed all my concerns. I recommend it for publication.", "reviewer_3": "Lan et al have resubmitted their manuscript on exciton coupling to magnons in a CrSBr/Fe3GaTe2 heterostructure. They have sufficiently addressed all my technical comments, but I remain concerned about the overall impact of their results and whether their claims are overstated given the very small effect they report. They still have hyperbolic language in the text: \"a breakthrough observation\", etc. which seems to me unjustified. They have failed to explain why a 6 meV shift in a 1.3 eV feature (a 0.5% effect) that is 100 meV wide is enough to constitute a breakthrough or be practically useful for spintronics.\nI can imagine that if this effect could be enhanced this would be useful--but as it is, these results on their own seem neither particularly surprising or impressive.\nOn that note, I must insist on my previous request: that the authors explicitly state in the abstract and conclusion the percent modulation of the exciton energies they observe relative to the total bandwidth. The authors stated instead the percent of the shift of magnetic field, which is not what I asked. The casual reader who glances through just the abstract and conclusion needs to know exactly how large this effect is. Transparency about the magnitude is of utmost importance.\nThese results warrant publication somewhere, but unless the authors can clearly explain why their effect is as useful and breakthrough as they claim, it is perhaps not appropriate for the wide readership of Nature Communications."}, "author_response": "Response to Reviewers and a Summary of Changes\nMany thanks to the reviewers for having given us valuable comments on the manuscript\n(NCOMMS-25-47700-A) submitted to Nature Communications.\nTitle: Spin hardening-boosted coherent magnon-exciton coupling in van der Waals\nheterostructure\nAuthors: Weican Lan, Chaocheng Liu, Ruiqi Liu, Yafei Chu, Lu Cheng, Yajuan Feng,\nChao Wang, Huijuan Wang, Minghui Fan, Yuran Niu, Hengli Duan, Wensheng Yan\nThe reviewers presented professional comments and revision suggestions before the\npaper could be reconsidered for publication in Nature Communications. Their insights\nhave been invaluable in guiding us towards enhancing the quality and clarity of our\nmanuscript. We have seriously considered these suggestions and comments, made the\nrevision accordingly, and would like to resubmit the revised manuscript. We sincerely\nappreciate the hard work of the reviewers and hope that the revised manuscript can meet\nthe acceptance criteria. The detailed responses to the comments are presented in a point-\nto-point manner as follows. Accordingly, all responses to reviewers' comments are\nhighlighted in blue; all revisions in the manuscript and supplementary files are\nhighlighted in red.\n------------------------------------\nResponse to Reviewer #3\n------------------------------------\nLan et al have resubmitted their manuscript on exciton coupling to magnons in a\nCrSBr/Fe GaTe heterostructure. They have sufficiently addressed all my technical\n3 2\ncomments, but I remain concerned about the overall impact of their results and whether\ntheir claims are overstated given the very small effect they report. They still have\nhyperbolic language in the text: \"a breakthrough observation\", etc. which seems to me\nunjustified. They have failed to explain why a 6 meV shift in a 1.3 eV feature (a 0.5%\neffect) that is 100 meV wide is enough to constitute a breakthrough or be practically\nuseful for spintronics. I can imagine that if this effect could be enhanced this would be\nuseful--but as it is, these results on their own seem neither particularly surprising or\nimpressive.\nOn that note, I must insist on my previous request: that the authors explicitly state in\nthe abstract and conclusion the percent modulation of the exciton energies they observe\nrelative to the total bandwidth. The authors stated instead the percent of the shift of\nmagnetic field, which is not what I asked. The casual reader who glances through just\nthe abstract and conclusion needs to know exactly how large this effect is.\nTransparency about the magnitude is of utmost importance.\nThese results warrant publication somewhere, but unless the authors can clearly explain\nwhy their effect is as useful and breakthrough as they claim, it is perhaps not appropriate\nfor the wide readership of Nature Communications.\nResponse: We sincerely thank the reviewer for the careful re-evaluation and\nconstructive comments on our revised manuscript. We appreciate the reviewer’s\nacknowledgment that our technical responses were satisfactory, and we have carefully\nconsidered the remaining concerns regarding the modulation magnitude of exciton\nenergy and the significance of our results. In addition, any hyperbolic language that\nappears in the text has been removed in accordance with your rigorous consideration.\nWe apologize for the oversight of not explicitly stating the percent modulation of the\nexciton energies relative to the total bandwidth. We are grateful for your reminder.\nAccording to your suggestion, we have explicitly stated this modulation amplitude and\nadded it to both the abstract and conclusion in our revised manuscript. We fully agree\nwith your viewpoint that transparency about this modulation magnitude is crucial for\ndirectly highlighting the exciton tuning effect. Accordingly, we have extracted and\nanalyzed the temperature-dependent PL data. Relative to the excitonic linewidth of\napproximately 100 meV, we achieved a bidirectional modulation of about 8.6%\n(redshift) and 6.1% (blueshift), as presented in Fig. R1. These shifts represent not only\nthe movement of the PL peak, but also that of the entire PL spectrum. Notably, although\nthe absolute modulation magnitude in this work is relatively limited, the exciton energy\nshift can switch between positive and negative states, enabling bidirectional modulation.\nSpecifically, relative to pristine CrSBr, we not only observe the generally reported\nredshift of the exciton energy but also discover an anomalous blueshift for the CrSBr\nin heterostructure. That is, we have achieved bidirectional modulation of the exciton\nenergy, which has not been accomplished in previous studies to the best of our\nknowledge. We believe that this bidirectional capability is of greater significance than\nthe magnitude alone, as it provides substantial flexibility in device design and paves the\nway for potential wavelength control in quantum information and optoelectronic\ntechnologies.\nMoreover, we would like to emphasize once again that the value and innovation of\nour work are mainly in two aspects: (1) The modulation scheme is extended from\nconventional unidirectional control to bidirectional tunability (i.e., the exciton energy\ncan be both red- and blue-shifted). This established a potential pathway for flexible\nexciton energy modulation on demand. (2) It demonstrates that exciton energy\nmodulation can be achieved purely through intrinsic interfacial interactions, without\nrelying on externally applied magnetic or electric fields.This establishes a distinct route\ntoward exciton control, which is desirable for developing compact and self-sustained\nopto-spintronic devices.\nFinally, we sincerely thank you for your careful review and constructive comments.\nWe hope that our responses and revisions have addressed all concerns. Our work\ndemonstrates the unique capability of bidirectional exciton energy modulation, which\nfalls within the field of exciton physics and opto-spintronic devices. We believe that\nthis study meets the high standards of Nature Communications and is of broad interest\nto its readership.\n1.3 1.4\nFig. R1. Temperature-dependent modulation of exciton energy relative to the excitonic\nlinewidth.The relative energy shift, expressed as a percentage of the excitonic linewidth (~100\nmeV), is plotted for three representative temperatures.\n)%EΔ(\nedutingam\ntfihs\nygrene\nredshift blueshift\n8.6%\n6.1%\nPhoton energy (eV)\nRevision:\nAccordingly, Fig. R1 with the relevant caption has been added on page 7 of the\nSupplementary Materials,as Fig. S6.\nThe original description on page 1 of the Main Text “Here we present an effective\nstrategy to modulate the exciton state of CrSBr via phonon-mediated magnon-exciton\ntripartite interactions in the CrSBr/Fe GaTe heterostructure.” has been changed to\n3 2\n“Here we achieve bidirectional modulation of the CrSBr exciton energy via phonon-\nmediated magnon-exciton tripartite interactions in a CrSBr/Fe GaTe heterostructure.\n3 2\nCompared with pristine CrSBr, the photoluminescence (PL) peaks in the\nheterostructure can exhibit blueshift and redshift corresponding to 6.1% and 8.6% of\nthe total bandwidth, respectively.”.\nThe original description on page 2 of the Main Text “Our findings demonstrate an\napproach for modest modulation of exciton energy in 2D AFM semiconductors, which\nmay provide insights for future exploration of wavelength control in quantum\ninformation and optoelectronic technologies such as communication and sensing.” has\nbeen changed to“Our findings demonstrate an approach for bidirectionally modulating\nexciton energy in 2D AFM semiconductors, which provides substantial flexibility in\ndevice design and offers an avenue for potential wavelength control in quantum\ninformation and optoelectronic technologies.”.\nThe original description on page 3 of the Main Text “Here, we report an\nunprecedented observation of coherent exciton coupling and orientation-enhanced\nelectron spin in a 2D magnetic heterostructure formed by CrSBr and Fe GaTe (FGT).”\n3 2\nhas been changed to “Here, we report coherent exciton coupling and orientation-\nenhanced electron spin in a 2D magnetic heterostructure formed by CrSBr and\nFe GaTe (FGT).”.\n3 2\nThe original description on page 3 of the Main Text “Moreover, with the devotion of\nthe coupled phonons, this interfacial coupling consequently leads to an anomalous\nincrease in photon emission energy.” has been changed to “Moreover, this interfacial\ncoupling achieves not only a general photon energy redshift but also an anomalous\nblueshift, attributed to the mediation of coupled phonons.”.\nThe original description on page 3 of the Main Text “Through magnetotransport tests,\nwe demonstrate this orientation-enhanced spin ordering in CrSBr, and simultaneously\nuncover that this coupling effect is reciprocal, as it meanwhile strengthens the magnetic\nproperties of FGT.” has been changed to “Through magnetotransport tests, we\ndemonstrate the orientation-enhanced spin ordering in CrSBr, and simultaneously\nuncover that interfacial magnetic coupling is reciprocal, as it meanwhile strengthens\nthe magnetic properties of FGT.”.\nThe original description on page 3 of the Main Text “Consequently, the intrinsic AFM\nfeatures are well-preserved, and the exciton energy of CrSBr demonstrates the\ncapability for selective modulation that is dependent on spin order.” has been changed\nto“Consequently, the intrinsic AFM features are well-preserved, and the exciton energy\nof CrSBr demonstrates the capability for bidirectional modulation dependent on spin\norder.”.\nThe original description on page 4 of the Main Text “Our work provides a novel\napproach for designing coherent behavior between magnons and excitons, laying the\nfoundation for the application of a class of AFM semiconductors, exemplified by CrSBr,\nin the field of opto-spintronics.” has been changed to“Our work provides an approach\nfor designing coherent behavior between magnons and excitons, offering new insights\ninto the potential application of AFM semiconductors, exemplified by CrSBr, in the\nfield of opto-spintronics.”.\nThe original description on page 6 of the Main Text “Furthermore, we observe that\nthe temperature-dependent PL spectra exhibit higher photon energy below the T for\nN\nthe CrSBr on FGT, compared to pristine CrSBr (Fig. 2c), suggesting a correlation with\nits AFM phase transition under the action of FGT.” has been changed to“Furthermore,\nwe observe that the temperature-dependent PL spectra exhibit higher photon energy\n(blueshift) below the T for the CrSBr on FGT, compared to pristine CrSBr (Fig. 2c),\nN\nsuggesting a correlation with its AFM phase transition under the action of FGT.”.\nThe original description on page 6 of the Main Text “Within these temperature ranges,\nCrSBr/FGT exhibits even lower photon energies compared to pristine CrSBr, achieving\na maximum difference of around 200 K.” has been changed to “Within these\ntemperature ranges, CrSBr/FGT exhibits even lower photon energies (redshift)\ncompared to pristine CrSBr, achieving a maximum difference of around 200 K.”.\nThe original description on page 6 of the Main Text “A step height of ±14 meV in\nexciton energy is acquired across critical temperature T , with its magnitude being\nN\ncomparable to the theoretical energy threshold under magnetic order modulation via\nexternal magnetic fields.” has been changed to “Compared with pristine CrSBr, a step\nheight greater than 14 meV in photon energy is observed across the critical temperature\n(T ) in the heterostructure, with a bidirectional modulation magnitude of approximately\nN\n6.1% (blueshift) and 8.6% (redshift) relative to the total excitonic linewidth of ~100\nmeV (Fig. S6).”.\nThe original description on page 14 of the Main Text “The tunable exciton energy\nbetween positive and negative states, dependent on magnon-exciton coupling, may\nunlock groundbreaking potential for arbitrary manipulation of exciton energies to\nenable precise control over the quantum states of excitons in quantum information\nstorage.” has been changed to “The bidirectional tunable exciton energy between\npositive and negative states, dependent on magnon-exciton coupling, may unlock the\npotential for arbitrary manipulation of exciton energies to enable precise control over\nthe quantum states of excitons in quantum information storage.”.\nThe original description on page 15 of the Main Text “In summary, we report a\nbreakthrough observation of coherent exciton coupling and orientation-enhanced\nelectron spin dynamics in a 2D CrSBr/FGT magnetic heterostructure.” has been\nchanged to “In summary, we report coherent exciton coupling and orientation-\nenhanced electron spin dynamics in a 2D CrSBr/FGT magnetic heterostructure.”.\nThe original description on page 15 of the Main Text “Moreover, the coherently\ncoupled exciton, which is affected by phonon-intervened magnon propagation as well,\nleads to an anomalous photon emission energy increase below T .” has been changed\nN\nto“Moreover, the coherently coupled exciton, which is affected by phonon-intervened\nmagnon propagation as well, leads to an anomalous photon emission energy blueshift\nbelow T .”.\nN\nThe original description on page 15 of the Main Text “Notably, the exciton energy\nshift achieved in our work can reach 40% of the modulation amplitude achievable with\nexternal magnetic fields[32,35], indicating a substantial level of modulation and offering\na valuable reference for future studies on wavelength control in laser systems.” has\nbeen changed to “Notably, the exciton energy shift can be bidirectionally modulated\nbetween positive and negative states relative to pristine CrSBr, with the magnitude of\nblueshift and redshift exceeding 6% and 8% of the total bandwidth, respectively. This\nbidirectional control highlights significant flexibility in device design and offers a\nvaluable reference for future studies on wavelength control in laser systems.”.\nThe original description on page 15 of the Main Text “Our findings advance a\npowerful strategy to tailor magnon-exciton coherence, opening avenues for AFM\nsemiconductors like CrSBr in opto-spintronic devices such as spin-logic gates and\nnonvolatile magneto-optical memory systems.” has been changed to “Our findings\npresent an effective strategy to tailor magnon-exciton coherence, opening avenues for\nAFM semiconductors like CrSBr in opto-spintronic devices such as spin-logic gates\nand nonvolatile magneto-optical memory systems.”."}, {"round": 3, "reviewer_comments": {"reviewer_3": "I thank the authors for putting the shift relative to total bandwidth in the abstract. I now am satisfied that my previous concerns have been met.", "reviewer_4": "The manuscript entitled \"Spin hardening-boosted coherent magnon-exciton coupling in van der Waals heterostructure\"\nrepresents an impressively wide collection of experimental results comparing the properties of CrSBr and CrSBr/FGT\nheterostructures. The experiments are of high quality. However, I agree with previous referees that the broad implications of\nthe results are overstated, and I find that the totality of the results do not seem to come together into a coherent story.\nThe first main deficiency of the paper is that it asserts a lot of mechanisms for the observed properties without distinguishing\nthose mechanisms from other possibilities or demonstrating consistency with the experiments through e.g. the use of\nsimulations or models. Unless it can be made precise what their mechanisms are predicting, it is not clear that they are\ncorrect. The second main deficiency is that many terms are ill-defined (e.g. spin-hardening, tripartite interaction), and\nultimately come across more as a phenomenological description of the experimental data rather than a clearly defined\nmicroscopic explanation. Sometimes different parts of the manuscript seem to be referring to different mechanisms for the\nsame observation, which further adds to the confusion. The third deficiency is the overall results are underwhelming: the\nmain conclusion that a small shift of the exciton PL, increase in saturation field, etc. can be induced by interfacial effects is\nnot surprising.\nWith these comments, I do not recommend publication in Nature Communications.\nTo aid the discussion I provide a detailed discussion of some aspects, which align with some comments of previous\nreferees.\n1. What is the meaning of \"phonon-mediated magnon-exciton tripartite interactions\"?\nIt seems the temperature dependence of the PL and Raman data in Fig. 2 can be attributed to regular thermal expansion and\nmagneto-elastic coupling. It is clear that the exciton energy may be influenced by the local crystalline environment; Cr(III)\ncomplexes display a wide range of PL emission energies ... Cr(III) PL in rubies is of course famously used for in-situ\npressure sensors. It is clear the structure has a temperature dependence, through anharmonicity and in response to the\nmagnetic correlations. These effects would be expected to be modified in the heterostructures due to differences in thermal\nexpansivity and magneto-elastic coupling in combination with interfacial strain or charge transfer, so that CrSBr and\nCrSBr/FGT would be expected to display slightly different temperature dependence of the PL and phonon Raman response.\nI do not find the observations surprising.\nIs the author's scenario the same or different from these conventional effects?\nIf it is the same, there is no need for a new name for these effects.\nIf it is different, the authors should indicate how it differs from conventional effects, present theory showing how it may be\ndistinguished, and demonstrate it experimentally.\n2. Is the \"spin hardening\" a consequence of exchange coupling between the FGT and the CrSBr, or a modification of the\nmagnetic anisotropy (for example via charge transfer or strain)?\nFirst, it should be noted that the magnetic anisotropy of FGT and related compounds is sensitive to both the Fe valency and\nstrain (see discussion in Wu, S. et al Nature Communications 15, 10765 (2024)).\nSecond, the increase of the saturation field of CrSBr when in contact with FGT seems to scale linearly with the magnetic\norder parameter of CrSBr, which would be the expected result if the magnetic anisotropy of CrSBr were increased or\nexchange between CrSBr layers was increased. If it were the direct result of exchange coupling with the FGT, it would be\nexpected to scale with the magnetization of the FGT, which it does not.\nThe discussion of this effect is confusing in the text.\nFor example, page 12 reads: \"the interfacial charge transfer can simultaneously modify the electronic structure of Cr, thereby\nexerting a profound impact on macroscopic magnetic properties. Specifically, the increased electron occupancy in Cr-3d\norbitals of CrSBr enhances their electron cloud density and amplifies the spatial overlap of adjacent Cr atomic orbitals[52-\n54]. As a result, the strengthened orbital hybridization and Cr-Cr AFM coupling further stabilize the AFM spins along the\nzigzag chains and enhance the magnetic proximity interactions between CrSBr and FGT, collectively contributing to the spin\nhardening and the suppressed lattice vibration.\"\nHere it seems to imply that charge transfer results in a modification of the magnetic couplings within the CrSBr.\nHowever, the conclusion reads \"We demonstrate that the robust interfacial magnetic exchange interactions from FGT harden\nthe AFM spin ordering in CrSBr, which therefore modifies the vibrational polarity of magnetic ions and elevates the spin-flop\nfield.\"\nHere it seems to imply magnetic exchange interactions between FGT and CrSBr, not charge transfer. What do the authors\nmean? What is meant by vibrational polarity?\n3. I do not view the collected data as unique indication of coherent exciton-magnon coupling.\nFirst, demonstrating that the PL is influenced by the magnetic state of the material is not sufficient to imply coherent exciton-\nmagnon coupling; as noted above, the PL may be influenced by effects like strain and charge transfer, which are clearly\nimplied by the other measurements. The fact that the structure (and therefore every other property) is sensitive to the\nmagnetic ground state through magneto-elastic coupling is not the same as coherent coupling of the exciton to magnetic\nexcitations above the ground state. Here is a place where an explicit model, with precise predictions for the temperature or\nfield dependence, should have been employed to justify the uniqueness of the conclusions of the manuscript.\nSecond, the PL in CrSBr has previously been demonstrated to have significant vibrational fine structure (see Lin et al, ACS\nNano 2024, 18, 2898, which should have been cited in the present work). Much of the observed lineshape is likely\ndominated by this fine structure. It is more accurate to say that the lineshape (including the large vibrational contribution) has\nbeen modified by FGT, but it is not clear the fundamental exciton has shifted. In Fig. 2c there are clearly differences in the\nlineshapes and linewidths, making the peak position itself a complicated measure of any effect.\nThird, it must be remarked that the slope of the PL peak energy as a function of temperature remains similar for T > T_N\nand T < T_N. However, for T > T_N there are no coherent magnons to couple with. It is stated in the main text: \"we perform a\nfitting analysis of the exciton peak shift using the power-law dependence of the AFM transition and yield a well-fitted result\n(Fig. S5), which further provides compelling evidence for coherent magnon-exciton coupling in the heterostructure.\"\nHowever, the power law fitting of the peak position in Fig. S5 is not very compelling at all. The data shows a continuous shift\nof the peak energy that is considerably more broad than the fitted function, suggesting there are mechanisms other than\nmagnetic ordering contributing to the shift.\nAs an additional comment: the extraction of the peak energy itself does not appear consistent across different figures. What\nis the meaning of the black lines in Fig. 2(a,b)? Why do they not match the peak positions plotted in Fig. 2d? Why do the\npositions of the arrows in Fig. 2c not correspond to the maxima of the curves, and also not match the peak positions in Fig.\n2d? (e.g. the arrows at 250 and 200K in Fig. 2c appear to be at the same energy, but they are not in Fig. 2d).\nAlso: the caption of Fig. S5 says that it was fit to a function with I^(2w), but this is not second harmonic generation; it is PL\npeak position. It is not clear why I^(2w) appears in this expression. The same expression appears in the caption of Fig. S12,\nwhich addresses Raman phonon peak intensity, which is also not I^(2w).\n4. I do not see the emphasized finding of bidirectional modulation of PL peak energy to be very remarkable.\nCr(III) compounds show a range of PL energies. It can be expected that the PL peak energy can be modified by chemistry,\nstrain, charge doping, etc. The stated novelty of some recent works in this area has been the observation that external fields\nmay additionally be used to control the PL peak energy in a single sample at a fixed temperature. The present finding that\nthe PL peak can also be tuned by interfacial effects is not in the same category as these recent works, because it cannot be\ncontrolled by external stimuli. The shifts are also a small percentage of the bandwidth, which limits the utility, as previous\nreferees have noted."}, "author_response": "Response to Reviewers and a Summary of Changes\nMany thanks to the reviewers for having given us valuable comments on the manuscript\n(NCOMMS-25-47700-B) submitted to Nature Communications.\nTitle: Spin hardening-boosted coherent magnon-exciton coupling in van der Waals\nheterostructure\nAuthors: Weican Lan, Chaocheng Liu, Ruiqi Liu, Yafei Chu, Lu Cheng, Yajuan Feng,\nChao Wang, Huijuan Wang, Minghui Fan, Yuran Niu, Hengli Duan, Wensheng Yan\nThe reviewers presented professional comments and revision suggestions before the\npaper could be reconsidered for publication in Nature Communications. Their insights\nhave been invaluable in guiding us towards enhancing the quality and clarity of our\nmanuscript. We have seriously considered these suggestions and comments, made the\nrevision accordingly, and would like to resubmit the revised manuscript. We sincerely\nappreciate the hard work of the reviewers and hope that the revised manuscript can meet\nthe acceptance criteria. The detailed responses to the comments are presented in a point-\nto-point manner as follows. Accordingly, all responses to reviewers' comments are\nhighlighted in blue; all revisions in the manuscript and supplementary files are\nhighlighted in red.\nAll revisions, along with the supplementary results and discussion (including those\nfrom the XMCD-PEEM measurements, DFT calculations, and micromagnetic\nsimulations), have been incorporated into the revised paper.\n------------------------------------\nResponse to Reviewer #4\n------------------------------------\nThe manuscript entitled \"Spin hardening-boosted coherent magnon-exciton coupling in\nvan der Waals heterostructure\" represents an impressively wide collection of\nexperimental results comparing the properties of CrSBr and CrSBr/FGT\nheterostructures. The experiments are of high quality. However, I agree with previous\nreferees that the broad implications of the results are overstated, and I find that the\ntotality of the results do not seem to come together into a coherent story.\nWe sincerely appreciate your constructive comments on our manuscript. Regarding\nyour concern about the potential overstatement of the broader implications of our\nresults, we would like to emphasize that this issue had already been thoroughly\nreviewed and addressed during the previous round of revisions. We had carefully\nrevised the entire manuscript in response to similar comments raised earlier, and these\nrevisions were acknowledged and approved by Reviewer #3. As noted in his/her most\nrecent report: “They have sufficiently addressed all my technical comments.” and “I\nthank the authors for putting the shift relative to total bandwidth in the abstract. I now\nam satisfied that my previous concerns have been met.” Accordingly, Reviewer #3\nagreed that the manuscript is suitable for publication.\nTo ensure a coherent narrative and logical progression, our study was structured\naround a motivation-observation-analysis-verification framework. We began by\nbuilding the CrSBr/FGT heterostructure, motivated by the potential of interfacial\nmagnetic interactions to modulate excitonic properties, and characterized its structure\nand basic physical properties (Fig. 1). We then employed PL measurements to reveal\nhow the interfacial coupling influences the optical response of CrSBr, from which we\ninferred a coupling relationship between magnetic order and excitons(Fig. 2).\nSubsequently, Hall transport measurements (Fig. 3) were carried out to examine how\nthis coupling affects spin orientation, confirming an interface-induced enhancement of\nspin alignment (i.e., enhanced magnetic anisotropy). Finally, we further validated the\ninterfacial magnetic interaction and clarified the fundamental driving mechanism\nbehind the exciton energy shift through XAS, PEEM, as well as newly added theoretical\ncalculations and micromagnetic simulations (Figs.4-5). These results collectively\nestablish and refine the charge-transfer-assisted interfacial magnetic coupling\nmechanism on exciton energy shift.\nTaken together, the overall structure and logical sequence of our work form a\ncoherent, self-consistent, and closed-loop narrative from experimental observations to\nmicroscopic mechanism verification.\nThe first main deficiency of the paper is that it asserts a lot of mechanisms for the\nobserved properties without distinguishing those mechanisms from other possibilities\nor demonstrating consistency with the experiments through e.g. the use of\nsimulations or models. Unless it can be made precise what their mechanisms are predicting, it is not\nclear that they are correct.\nThe second main deficiency is that many terms are ill-defined (e.g. spin-hardening,\ntripartite interaction), and ultimately come across more as a phenomenological\ndescription of the experimental data rather than a clearly defined microscopic\nexplanation. Sometimes different parts of the manuscript seem to be referring to\ndifferent mechanisms for the same observation, which further adds to the confusion.\nThe third deficiency is the overall results are underwhelming: the main conclusion that\na small shift of the exciton PL, increase in saturation field, etc. can be induced by\ninterfacial effects is not surprising.\nResponse:Thank you very much for your thoughtful comments and careful evaluation\nof our work.\nFirst, according to your suggestions, we have supplemented the manuscript with\nadditional experiments, together with comprehensive simulations and first-principles\ncalculations, which together directly validate our experimental observations. These\ncombined experimental and theoretical results allow us to clarify, from a microscopic\nperspective, the physical origin of the interface magnetic coupling driven by charge\ntransfer, thereby providing more solid and comprehensive evidence for the overall\nphysical picture: the charge transfer introduces additional spin polarization in CrSBr,\nthereby increasing its spin density and enhancing the interfacial magnetic interaction.\nThrough their cooperative effect, both the exchange interaction strength and the\nmagnetic anisotropy of CrSBr are enhanced. When CrSBr remains in the\nantiferromagnetic phase, the strengthened exchange interaction and magnetic\nanisotropy further stabilize the intralayer spin configuration, thereby suppressing\ninterlayer charge hopping and the participation of interlayer excitons. This suppression\nreduces the contribution of interlayer electron-hole hybridization to optical transitions,\nultimately manifesting as a blue shift of the exciton emission.\nSpecifically, our key conclusions are as follows:\n1. Charge transfer occurs at the CrSBr/FGT interface\nThe occurred charge transfer manifests as a redistribution of magnetically charges\nassociated with magnetic ordering (Fig. R1 and Table R1).\n2. The identified interface magnetic coupling originates from charge transfer\nThe redistribution of charges at the interface modifies local electronic occupation and\ntunes the degree of orbital hybridization and overlap, thereby providing the essential\nelectronic-structure conditions for interface exchange interactions (including direct\nexchange, superexchange, and RKKY-type coupling). In other words, the charge\ntransfer between CrSBr and FGT alters the filling of interfacial d orbitals and the\nstrength of their hybridization, forming the microscopic basis for enhanced interface\nmagnetic exchange and magnetic anisotropy. This mechanism—“charge redistribution-\norbital hybridization-enhanced magnetic exchange/coupling”—has been well\nestablished in numerous theoretical and experimental studies [Phys. Rev. Applied 12,\n044010 (2019); Adv. Sci. 9, 2200186 (2022); ACS Nano 18, 12, 9232-9241 (2024); Rev.\nMod. Phys. 89, 025006 (2017); J. Am. Chem. Soc. 146, 49, 34070-34079 (2024)], all of\nwhich demonstrate that interfacial charge transfer is a key driving force for tuning\nexchange interactions and interface magnetism. Notably, we have directly confirmed\nthe existence of interface magnetic coupling by using DFT calculations and XMCD-\nPEEM tests (Figs. R1 and R2).\n3. The enhanced spin alignment of CrSBr along the magnetic easy axis\nGrazing-incidence XPEEM measurements first reveal that the magnetic domain\nconfiguration of CrSBr (Fig. R2) is strongly influenced by the underlying FGT layer,\nproviding direct experimental evidence for an interfacial magnetic interaction between\nthe two materials. To further elucidate the nature of this coupling, we performed\nmicromagnetic simulations. Micromagnetic simulation results (Fig. R3) show that both\nthe magnetic anisotropy and the exchange interaction strength of CrSBr in the\nheterostructure are increased, which is highly consistent with our observations of stable\nspin orientation in XPEEM and the enlarged coercive field in transport measurements.\nMeanwhile, first-principles calculations indicate an increase in the spin polarization\nrate difference of CrSBr (quantified by the asymmetry in spin-resolved charge density)\n(Fig. R4), which further reinforces its magnetic stability through enhanced spin-\ndependent Coulomb interactions.\n4. The effect of enhanced antiferromagnetism on exciton energy\nMost existing studies on tuning the exciton energy of CrSBr rely on applying an\nexternal magnetic field to drive the system from an interlayer antiferromagnetic (AFM)\nstate into a ferromagnetic (FM) state. The underlying mechanism is that, in the AFM\nphase, spins in adjacent layers are antiparallel, which strongly suppresses interlayer\nelectron-hole recombination. When an external magnetic field aligns the spins\nferromagnetically, spin-allowed interlayer charge transfer channels are opened, leading\nto enhanced interlayer electron-hole hybridization and a redshift of the exciton energy\n(see Fig. R5, reproduced from [Nat. Mater. 20, 1657-1662 (2021); Phys. Rev. B 111,\n075107 (2025)]).\nIn contrast, in our CrSBr/FGT heterostructure, the exchange interaction and magnetic\nanisotropy of CrSBr are enhanced by interfacial effects, which further stabilize the\nintralayer spin configuration and suppress interlayer charge hopping and interlayer\nexciton participation. As a result, the contribution of interlayer electron-hole\nhybridization to optical transitions is reduced, ultimately giving rise to the observed\nblueshift of the excitonic emission (Fig. R6).\nBased on the above analyses, the mechanism we now propose is fully self-consistent\nand explains the two central observations in the CrSBr/FGT heterostructure:\n(1) the enhanced antiferromagnetic order of CrSBr, manifested by increased\nexchange interaction strength and magnetic anisotropy;\n(2) the anomalous blueshift of the CrSBr exciton energy.\nOverall, we have systematically reorganized the discussion of the physical\nmechanism in the revised manuscript. The description of the magnetic-exciton coupling\ndriven by interface magnetic interactions is now clearer, logically consistent, and well\naligned with both experimental and theoretical evidence. All relevant content has been\nthoroughly updated and clarified in the main text.\nSecond, we sincerely acknowledge that some descriptions regarding the underlying\nmechanisms in the previous version were not sufficiently clear or rigorous, which may\nhave caused potential misunderstanding or confusion for readers. In response to your\ncomments, we have systematically revised the relevant sections in the new manuscript:\nwe removed terms such as “spin hardening” and “coherent magnon-exciton coupling”,\nwhich may lead to ambiguity, and consistently adopted more physically accurate and\nexperimentally supported terminologies-namely “enhanced magnetic anisotropy” and\n“spin-exciton coupling.” In addition, based on the experimental data, we have\nthoroughly ruled out alternative factors such as strain and thermal expansion that could\notherwise influence the exciton energy (see detailed analyses in the revised manuscript).\nFinally, regarding the shift of the exciton PL peak, we would like to emphasize once\nagain that this issue has already been addressed in detail in our previous response.\nFor example, we previously stated:“Relative to pristine CrSBr, we not only observe the\ngenerally reported redshift of the exciton energy but also discover an anomalous\nblueshift for CrSBr in the heterostructure. That is, we have achieved bidirectional\nmodulation of the exciton energy, which, to the best of our knowledge, has not been\nrealized in previous studies. We believe that this bidirectional capability is of greater\nsignificance than the magnitude alone, as it provides substantial flexibility in device\ndesign and opens pathways toward potential wavelength control in quantum\ninformation and optoelectronic technologies.” These points have now been explicitly\nincluded in the revised manuscript. It is worth noting that the magnitude of the exciton\nenergy shift in our system is actually non-negligible in this research field, and more\nimportantly, we achieve bidirectional modulation of the PL exciton peak (both redshift\nand blueshift), which is a key discovery. The uniqueness and validity of this\nbidirectional modulation have been clearly acknowledged by Reviewer #3, as reflected\nin their comment:“I thank the authors for putting the shift relative to total bandwidth\nin the abstract. I now am satisfied that my previous concerns have been met.”\nCrSBr\nFGT\nFig. R1. The charge density differences for CrSBr/FGT heterostructure. The pink and\ngreen areas depict charge accumulation and depletion, respectively.\nTable R1. Amount of electron transfer. DFT calculated electronic transfer in CrSBr/FGT\nheterostructure. The symbol \"+\" denotes electron gain, while \"−\" represents electron loss. Unit:\ne/Å2.\nCrSBr FGT\n+0.007 −0.007\nFig. R2. XMCD-PEEM images of Cr L-edge acquired with a 16° X-ray incidence angle\nrelative to the sample surface. The red and green dashed lines mark the areas of CrSBr and\nFGT, respectively.\n450\n414.6\n130.5\n400\n394.1 125.2\nCrSBr CrSBr/FGT CrSBr CrSBr/FGT\nFig. R3.Micromagnetic simulations based on the constructed heterostructure model and\nthe corresponding extracted energies. (a) Schematic of the four-layer model, consisting of\ntwo out-of-plane ferromagnetic FGT layers and two in-plane antiferromagnetic FGT layers. (b)\nMicromagnetic simulation results of the exchange interaction and magnetic anisotropy energies\nof CrSBr in the pristine and heterostructure. Procedure for micromagnetic parameter extraction:\nfirst, the interlayer coupling in the heterostructure is turned off (i.e., FGT and CrSBr are treated\nas independent regions), after which the anisotropy and exchange energies are extracted for\neach layer. Then, the interlayer coupling is enabled, the anisotropy and exchange energies are\nre-evaluated for comparison.\n)Ve(\nygrene\nyportosinA\n160\n140\n120\n)Ve(\nygrene\negnahcxE\na b\nAnisotropy Exchange\nCrSBr\nFGT\nFig. R4.The spin polarization rate difference ( ) of CrSBr in the heterostructure, which\ncan be expressed as\n𝜟𝑷\n. where and ℎd𝑒e𝑡n𝑒𝑟o𝑜te the ℎn𝑒u𝑡m𝑒𝑟b𝑜ers of ℎs𝑒p𝑡i𝑒n𝑟-𝑜up and sp𝐶i𝑟n𝑆-𝐵d𝑟own el𝐶e𝑟c𝑆t𝐵ro𝑟ns,\n𝛥𝑃 = |(𝑁𝑢𝑝 −𝑁𝑑𝑜𝑤𝑛 ) / 𝑁𝑡𝑜𝑡𝑎𝑙 | − |(𝑁𝑢𝑝 − 𝑁𝑑𝑜𝑤𝑛 ) /\n𝐶𝑟𝑆𝐵𝑟\nrespectively, and is the total number of electrons. The superscripts “hetero” and “CrSBr”\n𝑁𝑡𝑜𝑡𝑎𝑙 | 𝑁𝑢𝑝 𝑁𝑑𝑜𝑤𝑛\nrefer to the CrSBr in the CrSBr/FGT heterostructure and pristine CrSBr, respectively. The red\n𝑁𝑡𝑜𝑡\nand blue areas represent positive and negative values of the spin polarization rate difference,\nrespectively.\n[FIGURE REDACTED]\nFig. R5 Schematic illustration of the effect of spin alignment on interlayer exciton\nbehavior in CrSBr. (a) [Nat. Mater. 20, 1657-1662 (2021)]. (b) [Phys. Rev. B 111, 075107\n(2025)]. In the AFM bilayer, interlayer antiferromagnetic order suppresses hybridization\nbetween layers, leading to the localization of spin-up and spin-down electrons at the top and\nbottom layers, respectively, near the doubly degenerate conduction band minima and valence\nband maximum. As a result, excitons are primarily intralayer, with the electron and hole\nconfined to the same layer, as confirmed by the side view of the exciton wavefunction (Fig. a-\nupper panel). In contrast, in the FM bilayer, interlayer hybridization is allowed, so the electron\nassociated with a hole fixed in one layer exhibits amplitude across both layers (Fig. a-lower\npanel), indicating enhanced interlayer electron-hole hybridization in the FM state, which leads\nto a redshift of the exciton energy.\nhv\nFM\nhv\nAFM\nFig. R6 Schematic illustration of the exciton recombination process in CrSBr under the\nenhanced antiferromagnetic configuration. The enhancement of antiferromagnetic exchange\ninteraction and magnetic anisotropy stabilizes the layer-resolved spin configuration, which\nfurther suppresses spin-allowed interlayer charge transfer and interlayer exciton formation. As\na result, exciton recombination is dominated by intralayer processes, giving rise to the observed\nblueshift of the exciton emission.\nRevision:\nAccordingly, Fig. R1, R3b, R4, R6 with the relevant caption has been added on page\n14 of the Main Text,as Fig. 5.\nAccordingly, Fig. R2 with the relevant caption has been added on page 12 of the\nMain Text,as Fig. 4i.\nAccordingly, Fig. R3a with the relevant caption has been added on page 21 of the\nSupplementary Materials,as Fig. S20.\nAccordingly, Table. R1 with the relevant caption has been added on page 22 of the\nSupplementary Materials,as Table. S1.\nThe supplementary description“Lastly, we discuss the anomalous increase of exciton\nenergy in CrSBr/FGT below T To understand this phenomenon from a microscopic\nN.\nperspective, we performed a series of theoretical calculations and simulations. Density\nfunctional theory (DFT) calculations reveal a pronounced redistribution of charge\ndensity in the CrSBr/FGT heterostructure (Fig. 5a). Quantitative charge analysis (Table\nS1, Supporting Information) shows a net electron transfer of approximately 0.007 e/Å2\nfrom FGT to CrSBr, in agreement with our KPFM and XAS measurements, further\nconfirming the existence of interfacial charge transfer. Notably, such charge transfer\noccurring between magnetic materials provides a crucial electronic-structure\nfoundation for the establishment of interfacial magnetic interaction. On this basis, we\nfurther extract the spin polarization rate difference ( ), of CrSBr in the heterostructure\nfrom the DFT calculations (Fig. 5b), which can be expressed as\n𝛥𝑃\n, where , anℎd𝑒𝑡 𝑒𝑟𝑜\n𝛥𝑃 = |(𝑁𝑢𝑝 −\nde ℎ n 𝑒 o 𝑡𝑒 t 𝑟 e 𝑜 the n ℎ u 𝑒𝑡 m 𝑒𝑟 b 𝑜 ers of 𝐶s𝑟p𝑆i𝐵n𝑟-up, s 𝐶 p 𝑟 i 𝑆 n 𝐵 - 𝑟 down 𝐶 𝑟 a 𝑆 n 𝐵 d 𝑟 total electrons, respectively. The\n𝑁𝑑𝑜𝑤𝑛 ) / 𝑁𝑡𝑜𝑡𝑎𝑙 |−|(𝑁𝑢𝑝 − 𝑁𝑑𝑜𝑤𝑛 ) / 𝑁𝑡𝑜𝑡𝑎𝑙 | 𝑁𝑢𝑝 𝑁𝑑𝑜𝑤𝑛 𝑁𝑡𝑜𝑡\nsuperscripts “hetero” and “CrSBr” refer to the CrSBr in the CrSBr/FGT heterostructure\nand pristine CrSBr, respectively. A positive indicates that the spin-polarized rate\nof CrSBr is enhanced in the heterostructure compared to pristine CrSBr, providing\n𝛥𝑃\ndirect microscopic electronic-structure evidence for the modulated spin configuration\nof CrSBr. To further elucidate how these electronic-structure modifications influence\nthe magnetic properties, we performed micromagnetic simulations based on parameters\nextracted from both experiments and theoretical calculations. Micromagnetic\nsimulations based on MuMax3 serve as a powerful tool for capturing the evolution of\nmagnetic energies and spin configurations in magnetic materials, particularly for our\nconstructed heterostructure model incorporating interlayer magnetic coupling between\nFGT and CrSBr (Fig. S20). The simulation results demonstrate that both the magnetic\nanisotropy energy and the exchange interaction energy of CrSBr are enhanced in the\nheterostructure (Fig. 5c), which is consistent with the emergence of magnetic single-\ndomain of CrSBr observed in the XMCD-PEEM measurement. This elevated magnetic\nenergy landscape effectively stabilizes the AFM spin configuration of CrSBr, which is\nin excellent agreement with the robust spin orientation in XMLD-PEEM and the\nincreased spin flip field in transport measurements, and is further supported by the\nenhanced spin polarization rate revealed by the DFT calculations.\nCombining the above experimental observations, micromagnetic simulations, and\nDFT calculations, we establish the following physical picture: interfacial charge-\ntransfer-driven magnetic coupling enhances the AFM ordering of CrSBr, manifested by\nthe concurrent enhancement of its exchange interaction and magnetic anisotropy. It is\nworth noting that for A-type AFM CrSBr, antiparallel spin alignment between adjacent\nlayers strongly suppresses interlayer electron-hole recombination. When an external\nmagnetic field or other perturbations drive the interlayer spins into a ferromagnetically\naligned configuration, spin-allowed interlayer charge transfer channels are opened,\nleading to enhanced interlayer electron-hole hybridization and a redshift of the exciton\nenergy. In contrast, in our CrSBr/FGT heterostructure, the interfacial magnetic\ninteraction further strengthens the AFM order of CrSBr, thereby more effectively\nsuppressing interlayer electron-hole recombination and significantly reducing its\ncontribution to optical transitions (Fig. 5d). Our work ultimately gives rise to an\nanomalous blueshift of the exciton emission energy below T through interfacial\nN\nmagnetic interaction. When the temperature exceeds the T of CrSBr, its AFM order\nN\ngradually diminishes, and the interfacial magnetic interaction-modulated ability\ncorrespondingly weakens, resulting in an abrupt change in the PL energy across the\nNéel temperature (Fig. 2d). In the temperature range above the T of CrSBr but below\nN\nthe T of FGT, ferromagnetically ordered FGT may still locally induce FM correlations\nC\nin CrSBr, which can reopen interlayer electronic hybridization channels and lead to a\nredshift of the exciton energy. As the temperature is further increased beyond the T of\nC\nFGT (above 300 K), this induced effect vanishes, and the exciton energy in the\nCrSBr/FGT heterostructure gradually converges to that of pristine CrSBr. This tunable\nexciton energy between blueshift and redshift, driven by interfacial magnetic\ninteraction-dependent spin-exciton coupling, may unlock the potential for arbitrary\nmanipulation of exciton energies to enable precise control over the quantum states of\nexcitons in quantum information storage.”has been added on page 13 of the Main Text.\nThe original description on page 1 of the abstract “Here we achieve bidirectional\nmodulation of the CrSBr exciton energy via phonon-mediated magnon-exciton\ntripartite interactions in a CrSBr/Fe GaTe heterostructure. Compared with pristine\n3 2\nCrSBr, the photoluminescence (PL) peaks in the heterostructure can exhibit blueshift\nand redshift corresponding to 6.1% and 8.6% of the total bandwidth, respectively. We\ndemonstrate a reciprocal spin-hardening behavior that is induced by interfacial\nmagnetic coupling and orbital-mediated charge transfer and that suppresses the phonon\nvibrations of magnetic ions.” has been changed to “Here we achieve bidirectional\nmodulation of the CrSBr exciton energy via interfacial interaction-modified spin-\nexciton coupling in a CrSBr/Fe GaTe (FGT) heterostructure. Compared with pristine\n3 2\nCrSBr, the photoluminescence (PL) peaks in the heterostructure can exhibit blueshift\nand redshift corresponding to 6.1% and 8.6% of the total bandwidth, respectively. We\nreveal that the interfacial charge-transfer-driven magnetic coupling in the\nheterostructure effectively enhances the magnetic anisotropy and the exchange\ninteraction of CrSBr, thereby stabilizing its AFM spin configuration, suppressing\ninterlayer electron-hole recombination, and ultimately leading to an anomalous\nblueshift of the exciton emission.”.\nThe original description on page 3 of the introduction “Here, we report coherent\nexciton coupling and orientation-enhanced electron spin in a 2D magnetic\nheterostructure formed by CrSBr and Fe GaTe (FGT). The features of phonon modes\n3 2\nand exciton PL in CrSBr exhibit a synergistic dependence on the magnetic transition\ntemperatures of both CrSBr and FGT, suggesting strong tripartite coupling among\nphonons, magnons, and excitons. Due to the robust interfacial magnetic exchange\ninteractions imparted by FGT, the easy-axis AFM spin ordering in CrSBr is hardened\nand reinforced orientationally, altering the vibrational polarity of the magnetic ions.\nMoreover, this interfacial coupling achieves not only a general photon energy redshift\nbut also an anomalous blueshift, attributed to the mediation of coupled phonons.\nThrough magnetotransport tests, we demonstrate the orientation-enhanced spin\nordering in CrSBr, and simultaneously uncover that interfacial magnetic coupling is\nreciprocal, as it meanwhile strengthens the magnetic properties of FGT. Furthermore,\nin combination with microscopic-level synchrotron X-ray photoemission electron\nmicroscopy (XPEEM), we reveal an orbital-mediated charge transfer mechanism (from\nFe e -orbital to Cr t -orbital) for stabilizing spin order (spin hardening), without\ng 2g\naltering the magnetic domain structure of either FGT or CrSBr. Consequently, the\nintrinsic AFM features are well-preserved, and the exciton energy of CrSBr\ndemonstrates the capability for bidirectional modulation dependent on spin order.” has\nbeen changed to “Here, we report interfacial magnetic interaction-modified spin-\nexciton coupling in a 2D magnetic heterostructure formed by CrSBr and FGT. The\nfeatures of exciton PL in CrSBr exhibit a tight dependence on the magnetic transition\ntemperatures of both CrSBr and FGT, suggesting the existence of spin-exciton coupling.\nIn contrast to the common PL redshift in CrSBr, we demonstrate that the exciton energy\nexhibits an anomalous blueshift, originating from the suppression of interlayer electron-\nhole recombination induced by interfacial magnetic interaction. Through\nmagnetotransport tests, we demonstrate the magnetic properties of both FGT and CrSBr\nare modulated by the interfacial interaction. Furthermore, in combination with\nmicroscopic-level synchrotron X-ray photoemission electron microscopy (XPEEM),\nwe reveal an orbital-mediated charge transfer mechanism (from Fe e -orbital to Cr t -\ng 2g\norbital) for the interfacial magnetic interaction between CrSBr and FGT, which alters\nthe magnetic domain of CrSBr. Micromagnetic simulations combined with theoretical\ncalculations further support that the observed excitonic blueshift originates from the\nsuppression of interlayer electron-hole recombination driven by interfacial magnetic\ninteractions. ”.\nThe original description on page 15 of the conclusion “In summary, we report\ncoherent exciton coupling and orientation-enhanced electron spin dynamics in a 2D\nCrSBr/FGT magnetic heterostructure. Under the effect of FM order in FGT, the phonon\nmodes and excitonic PL in CrSBr exhibit strong correlations with the magnetic phase\ntransition, demonstrating spin-phonon and magnon-exciton coupling. Moreover, the\ncoherently coupled exciton, which is affected by phonon-intervened magnon\npropagation as well, leads to an anomalous photon emission energy blueshift below T .\nN\nWe demonstrate that the robust interfacial magnetic exchange interactions from FGT\nharden the AFM spin ordering in CrSBr, which therefore modifies the vibrational\npolarity of magnetic ions and elevates the spin-flop field. Both magnetotransport and\nsynchrotron XPEEM confirm that this interfacial coupling, accompanied by a charge\ntransfer-mediated mechanism, not only orientationally enhances the spin ordering in\nCrSBr but also reciprocally amplifies the magnetization of FGT, all while preserving\ntheir intrinsic magnetic domain structures.” has been changed to “In summary, we\ndemonstrate the bidirectional tunability of exciton energy in a 2D CrSBr/FGT magnetic\nheterostructure, governed by spin-exciton coupling modified through interfacial\nmagnetic interactions. The FM order in FGT modulates the spin configuration of CrSBr,\nwhich is consistently reflected in the evolution of magnetic-sensitive exciton energy,\nleading to an anomalous photon emission energy blueshift below T .\nN\nThese results\nestablish a direct correlation between interfacial spin states and exciton energy,\nhighlighting spin-mediated control of excitonic properties in vdW heterostructures.\nBased on experimental measurements and theoretical simulations,we demonstrate that\nthe interfacial charge-transfer-driven magnetic coupling in the heterostructure enhances\nboth the magnetic anisotropy and exchange interaction of CrSBr, effectively stabilizing\nits AFM spin configuration, which suppresses interlayer electron-hole recombination\nand increases the spin-flip field.”.\nThe supplementary description “This enhanced magnetoresistance may also\ninfluence the interlayer electronic interactions, potentially affecting the excitonic\nbehavior.” has been added on page 8 of the Main Text.\nThe original description on page 8 of the Main Text “All these results declare that\nthe interfacial magnetic coupling in the CrSBr/FGT heterostructure is reciprocal, as it\nstrengthens the alignment of spin order for both CrSBr and FGT (spin hardening), and\naffects their electrical properties.” has been changed to “All these results declare that\nthe interfacial magnetic interaction in the CrSBr/FGT heterostructure is reciprocal,\nwhich affects the magentic properties of both CrSBr and FGT.”.\nThe original description on page 10 of the Main Text “All XPEEM data were\nrecorded after cooling from room temperature to 100 K under zero magnetic field with\nnormal incidence (90) of X-ray on the sample surface. This setup is sensitive to out-\nof-plane FM and in-plane AFM but cannot detect the in-plane FM domain.” has been\nchanged to “All XPEEM data were recorded at 100 K after zero-field cooling with\nnormal incidence (90) of X-ray on the sample surface. Exceptionally, Fig. 4i was\nmeasured using grazing-incidence of X-ray (16°). ”.\nThe supplementary description “To directly probe the in-plane magnetic domains of\nCrSBr and validate the interfacial interaction in the heterostructure, we further\nperformed Cr L-edge XMCD-PEEM measurements under grazing-incidence geometry\n(16°) (Fig. 4i), which enhances sensitivity to the in-plane magnetic component of Cr\nmoments. Notably, compared with the multidomain state of pristine CrSBr, CrSBr in\nthe heterostructure exhibits a magnetic single-domain with decreased magnetic contrast.\nThis direct observation clearly indicates that the enchanced magnetic domain wall\nenergy and decreased magnetic moment for CrSBr in CrSBr/FGT heterostructure,\nfurther demonstrating the presence of interfacial magnetic interaction between CrSBr\nand FGT.” has been added on page 10 of the Main Text.\nThe original description on page 11 of the Main Text “Based on the above discussion,\nalthough the magnetic coupling interactions in the CrSBr/FGT heterostructure enhance\nspin alignment to achieve a spin-hardened state, it does not alter their intrinsic AFM\nspin orientation or magnetic domain configuration.” has been changed to “Based on\nthe above discussion, although the interfacial magnetic interaction in the CrSBr/FGT\nheterostructure changes the magnetic domain of CrSBr, it does not alter the intrinsic\nAFM spin orientation.”.\nThe original description on page 11 of the Main Text “Specifically, the increased\nelectron occupancy in Cr-3d orbitals of CrSBr enhances their electron cloud density\nand amplifies the spatial overlap of adjacent Cr atomic orbitals. As a result, the\nstrengthened orbital hybridization and Cr-Cr AFM coupling further stabilize the AFM\nspins along the zigzag chains and enhance the magnetic proximity interactions between\nCrSBr and FGT, collectively contributing to the spin hardening and the suppressed\nlattice vibration.” has been changed to“Specifically, the increased electron occupancy\nin Cr-3d orbitals of CrSBr enhances their electron cloud density and amplifies the\nspatial overlap of adjacent Cr atomic orbitals, which in turn strengthens orbital\nhybridization, stabilizes the spin configuration, and reinforces the interfacial magnetic\ninteraction. ”."}, {"round": 4, "reviewer_comments": {"reviewer_4": "The authors have made a sincere and good faith effort to respond to the comments of all referees, and have added a\nsignificant amount of new analysis. The clarified descriptions make it possible to address the accuracy of their interpretation\nwith follow-up studies.\nAs Reviewer #4, I was asked to provide a first review after several rounds of review had occurred, and most of the points I\nraised were intended to confirm the validity of the same concerns raised by the other referees in previous rounds.\nThose other referees have now indicated they are satisfied. While the authors have not fully assuaged all of my concerns regarding\nthe interpretation of the collected data, it is not fair to the authors to relitigate those concerns.\nOn this basis, I recommend to accept."}, "author_response": "Response to Reviewers\nMany thanks to the reviewers for their recognition of our manuscript (NCOMMS-25-\n47700-C) submitted to Nature Communications.\nTitle: Spin-exciton coupling modified by interfacial magnetic interactions in a van der\nWaals heterostructure\nYafei Chu, Lu Cheng, Chao Wang, Huijuan Wang, Minghui Fan, Zixun Zhang, Yuran\nNiu, Jheng-Cyuan Lin, Francesco Maccherozzi, Hengli Duan, Wensheng Yan\nWe sincerely thank Reviewer #4 for the positive evaluation and the recommendation\nto accept our manuscript (NCOMMS-25-47700-C). The reviewer’s insightful\nsuggestions and constructive comments have enabled us to present our results more\nrigorously and clearly, and we believe the manuscript has been significantly improved\nas a result.\nWe especially appreciate the reviewer for the time and effort they have devoted\nthroughout the multiple rounds of review, as well as for acknowledging our efforts to\naddress the concerns of all reviewers through comprehensive analyses and clarified\ndescriptions."}]

Decision letter