{"id":"7c3ab9de-899a-4116-b919-0ef6334a0ca1","arxiv_id":"2411.08597","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"In a graphene/FePS3 heterostructure, low-field negative magnetoresistance persists up to 100 K and is attributed to electron-magnon coupling, with the effect suppressed for thinner FePS3 layers.","lead":"This paper finds that a few-layer graphene strip on antiferromagnetic FePS3 shows negative magnetoresistance at low fields up to 100 K, which the authors attribute to electrons coupling to magnons at the interface. The result could offer a simple electrical readout for antiferromagnetic magnons, with potential use in magnonic devices.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The negative MR in FLG/FePS3 is not yet separated from a field-induced carrier-density change: the paper's own magnetocapacitance data show a perpendicular field modifies the interface, and no Hall or gate-dependent measurement rules out n(B) as the origin.","rationale":"This is the single most load-bearing concern because it targets the causal mechanism stated in the strongest claim. The authors explicitly frame the result as negative MR from interfacial electron-magnon coupling leading to mobility enhancement, and the reader's own weakest_assumption is the same. A field-dependent carrier density would produce a negative MR without any spin-dependent scattering, so the central interpretation would collapse. The paper's magnetocapacitance data make this concern concrete rather than speculative: a perpendicular field changes the interfacial dielectric response in this material system, and the transport device uses the same FLG/FePS3 interface. None of the reported measurements (zero-field resistance vs temperature, gate sweep at zero field, in-plane-field MR) rules out a B-induced charge-transfer contribution. Secondary issues (no error bars, no non-magnetic control, magnon fit from the same data, temperature inconsistency between the 40 K/70 K softening and the persistence of negative MR to 100 K) all weaken the interpretation, but they could be repaired; a confirmed carrier-density confound would falsify it. The proposed Hall measurement settles the question directly. Because this is an experimental confound that is testable and the existing data are consistent with either mechanism, the appropriate verdict remains conditional: the paper should not be accepted as establishing electron-magnon-mediated magnetotransport until n(B) is measured.","tokens_in":15093,"tokens_out":6725,"duration_ms":62944,"concrete_test":"Fabricate a Hall-bar device on the same HS-1 stack (or measure the existing device in a Hall configuration) and measure the transverse resistance R_H(B) at T = 10, 50, 90, and 110 K for B⊥ from −1 T to +1 T. Extract the carrier density n(B) = 1/(e R_H(B)) over the same field range. Compute the expected resistance change from n(B) alone using the zero-field mobility μ(0) = R(0)/(L/W)/n(0) and compare with the measured R(B). If (R(n(B))−R(0))/R(0) reproduces the observed negative MR within experimental uncertainty, the negative MR is a density effect and the electron-magnon interpretation is unsupported. If n(B) is constant to within a few percent over ±0.2 T at all temperatures, the confound is cleared and the mobility-based EMC claim survives.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim is that the low-field negative MR in HS-1 reflects enhanced mobility from electron-magnon coupling, not carrier-density changes. This requires the carrier density n in the FLG channel to be constant as a function of B. The paper does not report a Hall measurement or any direct determination of n(B) on the transport device. The only field-dependent electrical quantity measured on a similar stack is the magnetocapacitance: in Section III, a 'significant drop in capacitance (−ΔC∼ 15 fF at 20 K)' is reported for FLG/FePS3/FLG under ±1 T, and the authors attribute this to interfacial magnetoelectric response. If the same field-dependent polarization/charge transfer occurs in the planar HS-1 device, then R(B)−R(0) in the MR definition [R(B)−R(0)]/R(0) could be dominated by a change in n rather than in mobility μ. In that case the B lnB fit and the extracted D′(T) of Fig. 4 would not identify the proposed mobility mechanism. The spatial correlation with the FePS3 region and the thickness dependence are consistent with an interfacial effect, but they do not distinguish an electrostatic (n-changing) mechanism from an electron-magnon (μ-changing) mechanism.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports temperature-dependent Raman and magnetotransport measurements on few-layer graphene (FLG) on antiferromagnetic FePS3, together with magnetocapacitance measurements on a FLG/FePS3/FLG sandwich. The central claims are that the magnon mode of FePS3 is softened in the heterostructure, that the effective magnon stiffness D' extracted from the magnetoresistance (MR) data decreases with cooling, and that a low-field negative MR in the FLG channel up to about 100 K arises from electron-magnon coupling at the interface (magnon-to-charge conversion). The negative MR is reported to be absent in FLG regions not in contact with FePS3 and suppressed when the FePS3 thickness is reduced. The paper also reports a negative magnetocapacitance below about 90 K, which is attributed to magnon-phonon coupling and interfacial polarization.","tokens_in":15390,"tokens_out":3983,"duration_ms":40423,"significance":"If substantiated, the result would provide a transport-based probe of antiferromagnetic magnons in van der Waals heterostructures and could motivate magnon-to-charge-conversion devices. The paper has several compensating strengths: the negative MR is spatially correlated with the FePS3 overlap region, the thickness dependence of the effect is shown, and the Raman data display spin-phonon anomalies and a magnon mode whose temperature dependence is tracked. The manuscript also presents a microscopic electron-magnon coupling Hamiltonian and a Boltzmann-transport sketch that makes a concrete J_em^2 dependence. However, the central causal claim is currently supported mainly by correlations: there is no direct measurement of carrier density versus magnetic field, no non-magnetic control, no error bars or device statistics, and the extracted D'(T) is a fitting output of the same MR data it is invoked to explain. These gaps are load-bearing for the proposed mobility-enhancement mechanism.","major_comments":[{"comment":"The effective magnon stiffness D'(T) shown in Fig. 4 is extracted by fitting the very low-field MR data whose negative slope is the observation to be explained. Because D'(T) is a free parameter of the B lnB fit, the statement that 'magnon stiffness decreases with cooling' is not an independent experimental result; it is a restatement of the fit. To break the circularity, the authors need either an independent determination of D(T) (for example from the measured magnon Raman shift or from literature INS values on FePS3) or a direct comparison of the fitted D'(T) to such data, with quantified uncertainties on the fit parameters.","section":"§III (formula Δρ ∝ B lnB / D(T)^2) and Fig. 4"},{"comment":"The paper does not rule out a magnetic-field-induced change in carrier density n(B) as the origin of the low-field negative MR. The only field-dependent electrical quantity measured on a similar stack is the magnetocapacitance of FLG/FePS3/FLG, which shows a significant drop of about 15 fF at 20 K under ±1 T and is attributed by the authors to interfacial magnetoelectric response. If a comparable field-dependent charge transfer or polarization change occurs at the planar HS-1 interface, then [R(B)−R(0)]/R(0) could be dominated by n(B) rather than by mobility enhancement. A Hall measurement or gate-dependent MR on the same transport device is required to establish that the resistance change reflects mobility, and this is the central load-bearing point for the electron-magnon mechanism.","section":"§III, Fig. 5 (magnetocapacitance) and absence of Hall measurement"},{"comment":"The temperature scale of the magnon softening is stated inconsistently. The abstract says the magnon mode 'softens below 40 K'; the main text says 'the magnon mode softens below 70 K' (near Fig. 4 and Supplementary Fig. SVII); and other passages describe softening or a blueshift with increasing temperature between 5 K and 120 K. The temperature dependence of the magnon and of D' is the backbone of the claimed mechanism, so the raw Raman frequencies at each temperature and a single explicit definition of the anomaly temperature must be provided.","section":"Abstract vs. §III and Fig. 4"},{"comment":"The magnetotransport data are presented for one device of each stack (HS-1, HS-2) without error bars, repeated measurement statistics, or instrument resolution. Fig. 3 shows no uncertainty estimates on the MR curves, and Fig. 4 reports D' without confidence intervals. Additionally, there is no non-magnetic control sample: the FLG-only regions within the same device establish spatial correlation with FePS3 but cannot separate antiferromagnetic magnon scattering from magnetostrictive, electrostatic, or trapped-charge interface effects. Adding a control stack with a non-magnetic isostructural or band-insulating van der Waals layer, or at least a clear measurement of number of devices and error bars, is necessary to support the specificity of the effect to magnons.","section":"§III, Fig. 3 and Fig. 4 (controls and error bars)"}],"minor_comments":[{"comment":"There are several typographical errors that should be corrected, including 'correleted' (main text near the G-band linewidth discussion), 'resiatance' and 'mesaured' (Fig. SIV caption), and 'enrgy' (Supplementary Information).","section":"Throughout"},{"comment":"The inset is labeled 'three zero-energy phonon (ZP) modes' but the modes have finite energy; this should be 'zone-folded phonon modes' to match the terminology used in the main text.","section":"Fig. 2 inset caption"},{"comment":"The field geometry is not fully defined in the text: B⊥ and B∥ are only introduced in the Fig. 3 caption, and the notation 'B⊥ I' in inset (a) is ambiguous. The authors should state explicitly the field and current directions for every MR trace.","section":"Fig. 3 and its insets"},{"comment":"The claim that the 'area under the curve in the negative MR region' decreases with temperature requires a definition of the integration range and how the zero baseline is subtracted; otherwise the reader cannot reproduce the trend.","section":"Fig. 3 inset (d)"},{"comment":"The high-field linear MR is cited to Ref. [29] (Morozov et al.), but the FLG-on-SiO2 behavior in that work is not directly compared with the slopes or intercepts reported here. A quantitative comparison, or a statement that only the functional form is being used, would improve clarity.","section":"§III, high-field linear MR"}],"recommendation":"major_revision","confidential_remarks":"The paper fits the journal scope, and I do not see a citation-integrity problem. The main issue is that the central claim (negative MR from electron-magnon coupling rather than from carrier-density changes) is not yet supported by the existing measurements. A Hall or gate-dependent measurement and an independent constraint on D(T) are feasible additions that would convert this from a correlational study into a mechanistic one; hence major revision rather than rejection."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Xiang—this one is worth a careful read, but the headline claim is not yet closed. The new thing is a negative magnetoresistance in few-layer graphene/FePS3 that shows up only when the measured stretch of graphene sits on the FePS3, persists to ~100 K, and weakens when the FePS3 is thinner. That is a clean-looking observation with a built-in spatial control, and the paper deserves credit for it, along with the Raman work showing enhanced spin-phonon coupling at the interface.\n\nThe soft spot is that the electron-magnon mechanism is supported by correlation, not by controls. The authors never measure the carrier density in the FLG channel as a function of field—no Hall, no gate-dependent MR that would separate n(B) from μ(B). That matters here more than usual because their own magnetocapacitance data on a FLG/FePS3/FLG stack show a ~15 fF drop under ±1 T, which they attribute to interfacial magnetoelectric response. If the same field-driven charge transfer happens in the planar device, then the negative MR could simply be a carrier-density effect, and the B lnB fit and the extracted D'(T) would not be identifying the proposed mobility mechanism. The thickness dependence and the spatial correlation are consistent with an interfacial effect, but they do not distinguish electrostatics from magnon physics.\n\nThere are also smaller issues. No error bars on the MR curves, no non-magnetic control, and an internal inconsistency in the magnon softening temperature: the abstract says the mode softens below 40 K, while the text says below 70 K. And the effective magnon stiffness D'(T) is obtained from fitting the very MR data it is meant to explain, so it cannot stand as independent confirmation.\n\nThe paper is honest about some of its limits and the Raman data are careful; the central observation is probably real. But the central claim—that this is electron-magnon coupling rather than field-induced charge transfer—needs a Hall measurement and a gate-dependence experiment before it can be taken as established. I would send it to referees, with the request that they push for those controls. It's a good discussion paper, but not yet a mechanism paper.","headline":"A real-looking negative MR in FLG/FePS3, but the magnon mechanism is underdetermined because no measurement rules out field-induced carrier-density changes in the graphene channel.","tokens_in":15854,"tokens_out":2092,"would_cite":false,"duration_ms":19722,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Graphene–FePS3 negative magnetoresistance comes from magnon coupling","keywords":["electron-magnon coupling","magnetoresistance","antiferromagnetic FePS3","few-layer graphene","van der Waals heterostructure","magnon-to-charge conversion","magnetocapacitance","Raman spectroscopy"],"falsifier":"Measure the carrier density (via Hall effect) in the same FLG/FePS3 device while sweeping the field through ±0.2 T at 10 K: if the negative magnetoresistance vanishes once resistance is divided by the field-dependent carrier density, the effect is a carrier-density artifact, not a magnon-driven mobility enhancement.","tokens_in":14920,"feed_emoji":"🧲","tokens_out":9472,"duration_ms":70997,"temperature":0.7,"pith_summary":"This paper tries to establish that a simple stacked device – few-layer graphene on the antiferromagnet FePS3 – converts magnons (quantized spin waves) in the FePS3 into an extra electric current in the graphene, and that this magnon-to-charge conversion shows up as negative magnetoresistance at low magnetic fields, persisting up to about 100 K. The authors argue this is an interfacial effect: surface electrons in the graphene couple asymmetrically to the two magnetic sublattices of FePS3, and a magnetic field stiffens the magnons so that they transfer momentum to the electrons more coherently. If true, it would give a purely electrical, contact-based probe of antiferromagnetic magnons, which are otherwise hard to detect because antiferromagnets have no net magnetization. Thickness-dependent measurements support the claim: thinning the FePS3 suppresses the negative magnetoresistance because the reduced magnetic moment weakens the coupling, and the magnetocapacitance upturn near 90 K points to a magnon-phonon contribution to interfacial polarization.","feed_headline":"Graphene–FePS3 negative magnetoresistance comes from magnon coupling","feed_subtitle":"Stacking few-layer graphene on FePS3 turns magnon motion into an electrical signal up to 100 K.","key_machinery":"The argument is carried by a phenomenological model of electron-magnon coupling at an uncompensated metal/antiferromagnet interface. The exchange Hamiltonian, $H_{\\mathrm{em}} = -J_{\\mathrm{em}}\\sqrt{S/2N}\\sum_{\\mathbf{k}\\mathbf{q}} \\Gamma_{\\mathbf{q}} c^\\dagger_{\\mathbf{k}+\\mathbf{q},\\downarrow}c_{\\mathbf{k},\\uparrow} + \\mathrm{H.c.}$, transfers angular momentum between graphene electrons and the two magnon sublattices, and a linearized Boltzmann treatment yields a magnon-induced current $j_{\\mathrm{em}}\\propto J_{\\mathrm{em}}^2$. The paper also uses the relation $\\Delta\\rho \\propto B\\ln B / D(T)^2$ (with $D$ the magnon stiffness) to fit the magnetoresistance and extract an effective stiffness $D'$ that decreases with cooling, linking the transport signature to the magnon softening seen in Raman spectroscopy. The key physical mechanism is that an applied field opens a magnon gap and increases magnon stiffness and coherence, improving momentum transfer from magnons to conduction electrons and thereby lowering resistance.","core_discovery":"The central claim is that the negative magnetoresistance observed in few-layer graphene when it sits on a thick FePS3 flake, at fields between -0.2 T and +0.2 T and temperatures up to 100 K, is a transport fingerprint of electron-magnon coupling at the interface. The paper supports this by showing that the magnon mode of FePS3 softens below 40 K and that the effective magnon stiffness extracted from the magnetoresistance data decreases on cooling, opposite to the pristine material; that the negative MR disappears above 100 K where phonon-dominated transport takes over; and that reducing FePS3 thickness from ~95 nm to ~30 nm suppresses the negative MR, consistent with weaker electron-magnon coupling. The authors rule out defects as the cause by noting the absence of a Raman D peak, and rule out weak localization by the persistence of negative MR up to 100 K. They further report a negative magnetocapacitance upturn below ~90 K in a FLG/FePS3/FLG capacitor, which they connect to magnon-phonon hybridization and interfacial electric displacement.","pith_inferences":["A direct extension would be to gate the few-layer graphene and check whether the negative MR amplitude tracks the density of states at the Fermi level; if it does, that would confirm the spin-flip scattering picture rather than a purely orbital magnetoresistance effect.","The same uncompensated-interface geometry could be replicated with other Dirac or semimetallic channels (for example monolayer graphene or thin topological-insulator films) to see whether the magnon-to-charge conversion efficiency scales with carrier mobility or spin coherence length.","If the magnon-stiffness interpretation is right, the temperature dependence of the extracted $D'(T)$ could be compared directly with inelastic neutron scattering on the same FePS3 batch, providing a quantitative check of the transport-based magnon probe."],"forward_implications":["FLG on FePS3 becomes an electrical detector of antiferromagnetic magnons up to 100 K, a temperature range where defect- or localization-based negative MR in graphene is not expected.","The FePS3 thickness is a tuning knob: thicker flakes give stronger electron–magnon coupling and larger negative MR, thinner flakes suppress it.","The negative-to-positive MR crossover near 100 K marks the boundary between magnon-assisted and phonon-dominated transport in the graphene channel.","The negative magnetocapacitance upturn near 90 K indicates that magnon–phonon coupling can alter the interfacial electric displacement, so capacitance measurements can track magnonic excitations."],"supporting_citations":[{"why":"Supplies the pristine FePS3 Raman baseline: spin-phonon modes, magnon mode at about 120 cm−1, zone-folded peaks, and magnon-stiffness temperature behavior that the heterostructure data are compared against.","marker":"[11]"},{"why":"Provides the thickness-dependence argument: detection of antiferromagnetic magnons via transport depends on interface and magnetic-layer thickness, used to explain suppression of negative MR in thinner FePS3.","marker":"[13]"},{"why":"Theoretical prediction of magnon-to-charge conversion at an uncompensated metal/antiferromagnetic-insulator interface, the framework the paper adopts for its FLG/FePS3 interface.","marker":"[25]"},{"why":"Documents mesoscopic corrugations and high-field linear magnetoresistance in few-layer graphene; the paper contrasts its low-field negative MR with these known graphene mechanisms.","marker":"[29]"},{"why":"Describes the chemical-vapor-transport growth of FePS3 and the Bi2Te3/FePS3 heterostructure, providing the sample-preparation route and the comparison where magnon stiffness changes under a Bi2Te3 overlayer.","marker":"[30]"},{"why":"Recent study of graphene/MnPSe3 heterostructure; the paper distinguishes its own negative MR and absence of Kondo effect from that system.","marker":"[41]"},{"why":"Supplies the relation Δρ ∝ B ln B / D(T)^2 used to fit magnetoresistance and extract the effective magnon stiffness D' versus temperature.","marker":"[51]"},{"why":"Gives pristine FePS3 magnetization and magnon-stiffness behavior below 60 K, and the magnetodielectric response of zigzag antiferromagnets used as baseline for the magnetocapacitance upturn.","marker":"[52]"},{"why":"Provides the electron-magnon coupling Hamiltonian and the Boltzmann-equation derivation showing the magnon-induced current jem scales as Jem^2, the theoretical backbone of the magnon-to-charge conversion interpretation.","marker":"[55]"}],"fun_headline_variants":["Magnon coupling drives negative magnetoresistance in graphene–FePS3","Graphene–FePS3 turns magnons into negative magnetoresistance","Electron-magnon coupling at graphene–FePS3 interface yields negative MR","How magnons shape magnetoresistance in graphene–FePS3 stacks","Thinner FePS3 weakens magnon coupling and suppresses graphene's negative MR"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The negative magnetoresistance is assumed to reflect a mobility boost from electron–magnon coupling, rather than a magnetic-field-induced change in the number of mobile carriers in the graphene (for example through the magnetocapacitance effect the authors themselves observe).","fun_headline_variants_meta":{"raw":{"variants":["Magnon coupling drives negative magnetoresistance in graphene–FePS3","Graphene–FePS3 turns magnons into negative magnetoresistance","Electron-magnon coupling at graphene–FePS3 interface yields negative MR","How magnons shape magnetoresistance in graphene–FePS3 stacks","Thinner FePS3 weakens magnon coupling and suppresses graphene's negative MR"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001125,"raw_usage":{"total_tokens":4707,"prompt_tokens":1002,"completion_tokens":3705,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":618,"completion_tokens_details":{"reasoning_tokens":3604}},"tokens_in":618,"tokens_out":3705,"duration_ms":25328,"temperature":1.0,"reasoning_tokens":3604,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T21:31:31.063636+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the carrier density (via Hall effect) in the same FLG/FePS3 device while sweeping the field through ±0.2 T at 10 K: if the negative magnetoresistance vanishes once resistance is divided by the field-dependent carrier density, the effect is a carrier-density artifact, not a magnon-driven mobility enhancement.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the thickness-dependence argument: detection of antiferromagnetic magnons via transport depends on interface and magnetic-layer thickness, used to explain suppression of negative MR in thinner FePS3."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Theoretical prediction of magnon-to-charge conversion at an uncompensated metal/antiferromagnetic-insulator interface, the framework the paper adopts for its FLG/FePS3 interface."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Documents mesoscopic corrugations and high-field linear magnetoresistance in few-layer graphene; the paper contrasts its low-field negative MR with these known graphene mechanisms."},{"cited_title":"Maity, D","cited_arxiv_id":null,"evidence_quote":"Describes the chemical-vapor-transport growth of FePS3 and the Bi2Te3/FePS3 heterostructure, providing the sample-preparation route and the comparison where magnon stiffness changes under a Bi2Te3 overlayer."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Recent study of graphene/MnPSe3 heterostructure; the paper distinguishes its own negative MR and absence of Kondo effect from that system."},{"cited_title":"Raquet, M","cited_arxiv_id":null,"evidence_quote":"Supplies the relation Δρ ∝ B ln B / D(T)^2 used to fit magnetoresistance and extract the effective magnon stiffness D' versus temperature."},{"cited_title":"Ghosh, M","cited_arxiv_id":null,"evidence_quote":"Gives pristine FePS3 magnetization and magnon-stiffness behavior below 60 K, and the magnetodielectric response of zigzag antiferromagnets used as baseline for the magnetocapacitance upturn."}],"review_version":1}