{"id":"1382d7d2-a7a5-4b3b-b5cf-644579ebfbdf","arxiv_id":"1908.07868","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"Graphene in contact with WS2 shows room-temperature spin Hall and spin galvanic conversion that is gate-tunable in magnitude and sign, with efficiency near the largest previously reported values.","lead":"Experiments with graphene next to a single layer of WS2 show a strong, gate-tunable conversion between charge and spin currents at room temperature, with two distinct spin-orbit effects separated by spin precession. The conversion efficiency peaks near the charge neutrality point and switches sign with carrier type, offering a ferromagnet-free route to generate and detect electron spins.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The conversion-efficiency extraction appears to use 200 K spin lifetimes to fit 300 K data; without a room-temperature spin-precession calibration, the quoted θ_SHE and α_SGE values may be systematically biased.","rationale":"The reader's CONDITIONAL verdict already identifies the anisotropic spin-diffusion model and the measured spin lifetimes as the weakest point. The sharpest concrete version of that concern is the apparent temperature mismatch: the spin lifetimes are extracted from data taken at 200 K, while the conversion-efficiency fits whose outputs feed the headline lambda_IEE values are to room-temperature data. The reader's formulation emphasized the use of lifetimes measured from a separate pair of electrodes and the completeness of the model, but did not explicitly flag the 200 K versus 300 K discrepancy. This is the most checkable possible failure mode: if the lifetimes change with temperature, the single scaling factor in the fit will absorb the temperature dependence of the spin transport and bias the quoted efficiencies. The main experimental evidence for the qualitative claim—antisymmetric Hanle lineshapes, reversal with magnetization orientation, gate-tunable sign change of the SGE, and insulating-character checks of WS2—remains credible, so this concern does not warrant rejecting the paper or declaring it unverified. It does, however, make the absolute efficiencies and the heavy-metal comparison conditional on an additional room-temperature calibration, which is exactly the kind of evidence the paper should provide. Since the reader already reached CONDITIONAL, the recommendation is UNCHANGED; the paper should be accepted with the condition that the room-temperature spin-precession calibration be supplied and the efficiencies re-derived, or that the comparison to heavy metals be softened to reflect the missing calibration.","tokens_in":11777,"tokens_out":10340,"duration_ms":107931,"concrete_test":"Re-obtain nonlocal spin-precession traces in the same device at 300 K using the F1-F3 and F1-F2 configurations of Figs. 2e/f, extract tau_s^||, tau_s^perp, and the diffusion constant at 300 K, and then re-fit the 300 K R_ISHE and R_SGE lineshapes of Figs. 2c/d with only theta_SHE and alpha_SGE as free scaling factors. If the resulting efficiencies, or the corresponding lambda_IEE values, deviate by more than about 50% from the quoted 0.3% and 0.1%, the heavy-metal comparison and the quantitative central claim should be revised. Alternatively, the authors should provide a direct comparison of 200 K and 300 K spin lifetimes in the same device demonstrating that they coincide within error.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The most load-bearing assumption is not the existence of proximity-induced spin-to-charge conversion, which the antisymmetric Hanle lineshapes support, but the quantitative calibration of the anisotropic spin-diffusion model used for the single-scaling-factor extraction. The spin transport parameters entering the model—tau_s^||=(6±1) ps and tau_s^perp=(52±10) ps, together with the associated diffusion constants—are obtained from nonlocal spin-precession measurements in Figs. 2e/f, and the caption states that measurements in a, b, e and f were performed at 200 K. The conversion efficiencies theta_SHE≈0.3% and alpha_SGE≈0.1% are then obtained by fitting room-temperature (300 K) Hanle traces in Figs. 2c/d with only the efficiency as a free parameter. No room-temperature spin-precession characterization is shown, and no statement is made that the spin transport parameters are temperature-independent over 200–300 K. If tau_s^||, tau_s^perp, or the diffusion constant changes with temperature, the scaling factor absorbs the resulting change in the calculated spin density at the detector, directly biasing theta_SHE and alpha_SGE. Since the headline comparison with heavy metals rests on lambda_IEE values (3.75 nm for the SHE channel and 0.42 nm for the SGE channel) computed from these efficiencies, this is a load-bearing omission. The authors' own admission that intrinsic theory under-predicts the SGE by about an order of magnitude, and that a large SHE is incompatible with the measured spin relaxation anisotropy, reinforces that the extraction model is not independently verified.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports nonlocal spin-precession measurements in monolayer graphene/WS2 Hall-bar devices, claiming room-temperature spin-to-charge (StC) conversion with separate contributions from the inverse spin Hall effect (ISHE) and the spin galvanic effect (SGE). The measurement scheme relies on the orthogonal spin orientations of the two effects: out-of-plane spins precess under in-plane fields to give the ISHE signal, while in-plane spins precess under out-of-plane fields to give the SGE signal. Using spin-transport parameters independently extracted from nonlocal Hanle measurements, the authors fit each antisymmetric lineshape with a single scaling factor, obtaining theta_SHE ~ 0.3% and alpha_SGE ~ 0.1% at room temperature. They further report gate-dependent conversion with a peak near the charge neutrality point, a sign change of the SGE between electrons and holes, and agreement of the SHE signal with a computed spin Hall conductivity as a function of carrier density and temperature.","tokens_in":12046,"tokens_out":6710,"duration_ms":68879,"significance":"If the quantitative extraction is correct, the result is significant: it would demonstrate electric-field-tunable, ferromagnet-free, room-temperature StC conversion in a van der Waals heterostructure, with lambda_IEEE values (3.75 nm for the SHE channel and 0.42 nm for the SGE channel) comparable to or larger than typical heavy-metal values. The measurement protocol has clear strengths: the antiparallel/parallel subtraction removes non-spin backgrounds, the SHE and SGE channels are separated by symmetry, and the spin-transport parameters entering the model are measured rather than freely adjusted. However, the central quantitative claims rest on a temperature-matching assumption that is not documented, and the quoted efficiencies lack uncertainty propagation. These issues, together with an over-stated comparison to intrinsic theory and an unaddressed discrepancy with a contemporaneous report, require revision before the quantitative conclusions can be accepted.","major_comments":[{"comment":"The spin-transport parameters used to compute the spin densities in the StC fits are extracted from measurements performed at 200 K, while the StC lineshapes in Figs. 2c and 2d are measured at 300 K. The caption explicitly states that measurements in Figs. 2a, 2b, 2e, and 2f are performed at 200 K, and the text quotes tau_s^|| = (6 +/- 1) ps and tau_s^perp = (52 +/- 10) ps from these data. The subsequent fits of the 300 K Hanle traces use these parameters with only the conversion efficiency as a scaling factor. If tau_s^||, tau_s^perp, or the diffusion constants change between 200 and 300 K, the scaling factor absorbs the resulting change in the calculated spin density at the detector, directly biasing theta_SHE and alpha_SGE and therefore the headline lambda_IEEE values of 3.75 nm and 0.42 nm. A room-temperature nonlocal spin-precession calibration on the same electrode pair, or a documented argument for temperature independence, is needed.","section":"Fig. 2 and main text (p. 5)"},{"comment":"The quoted efficiencies theta_SHE ~ 0.3% and alpha_SGE ~ 0.1% are given without uncertainties, despite the reported (6 +/- 1) ps and (52 +/- 10) ps spin lifetimes and the use of a one-parameter scaling fit. A propagation of these uncertainties through the Bloch-diffusion model, together with the fit uncertainty of the precession lineshapes, is required to support the quantitative comparison with Pt, Ta, W, Bi/Ag, and alpha-Sn. The claim that the agreement is 'excellent' should also be quantified, for example with residuals or a reduced chi-square metric.","section":"Fig. 2 and Section on StC conversion efficiencies"},{"comment":"The abstract and introduction state that the observed SHE conversion efficiency as a function of carrier density and temperature is 'well reproduced' by theoretical calculations of the spin Hall conductivity, but the Discussion acknowledges that intrinsic theory yields an alpha_SGE at least one order of magnitude smaller than the measured value and that a large SHE is incompatible with the observed anisotropic spin relaxation. The extrinsic mechanisms invoked (sulfur vacancies, resonant scattering) are not included in the Fig. 4b calculations. This internal tension should be resolved: either provide an explicit calculation including extrinsic contributions, or soften the claim to qualitative agreement for R*_ISHE and state clearly that the SGE magnitude is not captured by the intrinsic theory.","section":"Abstract, p. 2, and p. 8 (Discussion)"},{"comment":"The appended note states that Ref. [33], a study of the spin galvanic effect in graphene/WS2, does not observe SGE modulation or the SHE at room temperature. Because the central claim of the present manuscript is room-temperature coexistence of the SHE and SGE, this discrepancy is directly relevant to the paper's credibility. The authors should discuss possible origins of the difference, such as WS2/graphene interface quality, device geometry, the gate-voltage range, or measurement protocol, rather than merely citing the conflicting work.","section":"p. 8, Note referencing Ref. [33]"}],"minor_comments":[{"comment":"There are typos: 'interconvertion' should be 'interconversion', 'efficiencies' should be 'efficiencies', and 'substraction' should be 'subtraction'.","section":"Abstract and p. 2"},{"comment":"The phrase 'electrodes magnetizations' should be 'electrode magnetizations'.","section":"p. 4"},{"comment":"In the Device Fabrication section, 'subtrate' should be 'substrate', and 'two- and four-terminal measurements' would read better as 'two-terminal and four-terminal measurements'.","section":"Methods"},{"comment":"The description 'solid lines represent M1x' is ambiguous because the lines in Fig. 3a are green; the text should specify 'green solid lines' and use a consistent notation for the projected magnetization component.","section":"Fig. 3 caption and main text"},{"comment":"The inverse spin galvanic effect is abbreviated both ISGE and IGSE on p. 2; one abbreviation should be used consistently.","section":"p. 2 and throughout"},{"comment":"The inset of Fig. 4a claims R*_ISHE varies roughly as 1/T, but no fit line or fit uncertainty is shown; adding the fit and its parameters would make the claim quantitative.","section":"Fig. 4"}],"recommendation":"major_revision","confidential_remarks":"The technical concerns are centered on the temperature mismatch between the spin-transport characterization and the room-temperature conversion measurements, and on the absence of error bars for the headline efficiencies. These are fixable within the manuscript's scope. The discrepancy with Ref. [33] noted by the authors themselves may also merit editorial attention, but I do not see it as grounds for rejection given the strengths of the measurement protocol."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"First things first: this is a real experimental advance. The authors show room-temperature spin-to-charge conversion in graphene-WS2, separate the spin Hall and spin galvanic contributions using the orthogonality of their spin polarizations, and demonstrate gate control with opposite sign behavior for the SGE. The protocol is careful: they verify the WS2 is insulating in the gate range, use antiparallel/parallel subtraction to remove backgrounds, and characterize the anisotropic spin transport in the same device. That is solid work, and the antisymmetric Hanle lineshapes are convincing evidence that they are seeing spin signals.\n\nThe main soft spot is a temperature mismatch in the calibration. The spin lifetimes used in the extraction, tau_s^|| = 6 ps and tau_s^perp = 52 ps, come from measurements at 200 K (Fig. 2e/f), while the conversion efficiencies are extracted from room-temperature traces (Fig. 2c/d). The paper does not show that the spin lifetimes are unchanged between 200 and 300 K. If they vary, the single-scaling-factor fit absorbs the change and biases theta_SHE and alpha_SGE. This is not fatal to the qualitative story, but it means the quoted efficiencies and the comparison with heavy metals should be treated as provisional. The lack of error bars on the extracted efficiencies makes that worse.\n\nThe theory comparison in Fig. 4 is also weaker than the abstract suggests. The authors use parameters within a factor of two of DFT values to match the experimental temperature dependence, and they honestly state that the intrinsic theory under-predicts the SGE by an order of magnitude and cannot explain a large SHE alongside anisotropic spin relaxation. So the microscopic attribution is incomplete, not a clean confirmation.\n\nOverall, I think the core experimental observation holds: gate-tunable StC conversion, with SHE and SGE coexisting near the CNP, is a valuable result for the 2D spintronics community. The paper deserves serious peer review, but the reviewers should ask for a room-temperature spin-precession calibration or an explicit check of the 200-300 K temperature dependence, error bars, and a more careful discussion of what the theory actually constrains.\n\nI would bring it to reading group and probably cite it as evidence of proximity-induced StC conversion, but not for the absolute efficiency numbers.","headline":"Strong experimental paper with a real temperature-mismatch flaw in the efficiency extraction; worth refereeing but the headline numbers need caution.","tokens_in":12691,"tokens_out":1905,"would_cite":true,"duration_ms":18523,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Putting monolayer graphene on WS2 produces gate-tunable spin-to-charge conversion at room temperature, with efficiencies comparable to heavy metals.","keywords":["spin-to-charge conversion","spin Hall effect","inverse spin galvanic effect","graphene","WS2","proximity spin-orbit coupling","van der Waals heterostructures","room-temperature spintronics"],"falsifier":"Make devices with different WS2 strip widths and check that the extracted conversion lengths stay the same; if they vary, the single-channel diffusion model is missing physics. Alternatively, test Onsager reciprocity explicitly by swapping the injection and detection contacts and comparing the two measured voltages.","tokens_in":11495,"feed_emoji":"🧲","tokens_out":5321,"duration_ms":54235,"temperature":0.7,"pith_summary":"This paper claims that putting monolayer graphene in contact with the semiconductor WS2 creates a large, electrically tunable spin-to-charge conversion at room temperature. The conversion comes from proximity-induced spin-orbit coupling in the graphene and is carried by two distinct mechanisms, the spin Hall effect and the inverse spin galvanic effect, which the authors separate with spin precession measurements. If the claim holds, graphene-WS2 could serve as a ferromagnet-free building block for spin generation and for manipulating magnetization in ultra-compact memory devices, with efficiencies comparable to or better than platinum, tantalum, and tungsten.","feed_headline":"Room-temperature spin-to-charge conversion tuned by electric field","feed_subtitle":"Proximity to WS2 gives graphene heavy-metal-class spin conversion, switchable by gate voltage.","key_machinery":"The central mechanism is the spin texture that graphene inherits from WS2: proximity-induced spin-orbit coupling creates an out-of-plane spin component plus a winding in-plane texture, so the spin Hall effect and the inverse spin galvanic effect generate spins in orthogonal directions. The measurement protocol exploits that orthogonality: an in-plane magnetic field precesses only the spin-Hall-generated spins, while an out-of-plane field precesses only the spin-galvanic-generated spins. The argument is carried by the anisotropic Bloch diffusion equation, whose spin lifetimes are fixed from separate pristine-graphene and graphene-WS2 spin precession measurements, leaving each conversion efficiency as the single scaling factor in the fit.","core_discovery":"Using a Hall bar in which a WS2 flake covers one graphene arm, the authors measure nonlocal voltages while a ferromagnetic electrode injects spins, and they monitor the signal as a function of magnetic-field direction. The data show an antisymmetric spin-precession signal for an in-plane field, assigned to the inverse spin Hall effect, and for an out-of-plane field, assigned to the spin galvanic effect. All measurements are taken below the gate voltage at which WS2 becomes conducting, so the signals come from the proximity-modified graphene rather than from the WS2 itself. Fitting the anisotropic spin diffusion equation with independently measured spin lifetimes, tau_s^|| = (6 +/- 1) ps and tau_s^perp = (52 +/- 10) ps, they extract theta_SHE ~ 0.3% and alpha_SGE ~ 0.1%, which correspond to lambda_IEE values of about 3.75 nm and 0.42 nm. They also find that the inverse spin Hall signal peaks near the charge neutrality point while the spin galvanic signal changes sign between electron and hole doping, with the temperature dependence of the spin Hall signal consistent with calculations of the spin Hall conductivity.","pith_inferences":["If the gate-dependent sign change of the spin galvanic effect is robust, it could be used to write a ferromagnet with either polarity simply by choosing the gate voltage, without reversing the current direction.","The paper notes that intrinsic theory underestimates the measured spin galvanic efficiency; a testable extension is to intentionally introduce or remove sulphur vacancies in WS2 and track whether alpha_SGE changes, which would flag an extrinsic contribution.","Because the conversion happens at the graphene-WS2 interface, the same measurement protocol should transfer to other TMDC spacers, offering a systematic way to compare the strength of proximity spin-orbit coupling across materials.","The close match between the measured and computed temperature dependence of the spin Hall signal suggests that theta_SHE could be used as a quantitative probe of proximity spin-orbit coupling strength in other van der Waals pairs."],"forward_implications":["Room-temperature spin generation without ferromagnets becomes practical in a single graphene-WS2 layer, since both spin-to-charge and charge-to-spin conversion are demonstrated.","Electrostatic gating acts as a switch: the spin Hall signal peaks near the charge neutrality point, and the spin galvanic signal changes sign with carrier type, making the device a tunable spin conversion element.","The spin Hall conversion efficiency, lambda_IEE ~ 3.75 nm, is comparable to or larger than the values typically quoted for heavy metals, which makes van der Waals heterostructures competitive for spin-orbit-torque memory technologies.","Because the spin lifetimes are measured in the same device, the extracted efficiencies have no adjustable transport parameters and can be compared directly against computed spin Hall conductivities."],"supporting_citations":[{"why":"Establishes the strongly anisotropic spin relaxation in graphene-WS2 that the present analysis uses to fix the in-plane and out-of-plane spin lifetimes.","marker":"[14]"},{"why":"Provides the theoretical spin texture and band structure for graphene on TMDCs that motivates coexistence of spin Hall and spin galvanic effects.","marker":"[16]"},{"why":"Calculates the spin Hall conductivity in graphene/TMDC heterostructures used to compare against the measured gate and temperature dependence.","marker":"[19]"},{"why":"Predicts charge-to-spin conversion in graphene on TMDC and is used to benchmark the measured spin galvanic efficiency.","marker":"[20]"},{"why":"The original report of a spin Hall signal in graphene/WS2 that the paper revisits, noting follow-up work questioned its spin origin.","marker":"[21]"},{"why":"A room-temperature spin Hall effect in graphene/MoS2 that the paper distinguishes from its own signal by operating below the WS2 conduction threshold.","marker":"[25]"},{"why":"Supplies the spin precession-based measurement protocol used to separate the inverse spin Hall and spin galvanic contributions.","marker":"[29]"},{"why":"Gives the heavy-metal spin-to-charge conversion values for Pt, Ta, and W that are used to benchmark the measured efficiencies.","marker":"[31]"}],"fun_headline_variants":["Electric field switches spin conversion in graphene/WS2","Gate-tunable spin Hall and galvanic effects in graphene/WS2","Room-temp spin conversion tuned by gate in graphene/WS2","Gate-controlled spin conversion in graphene via WS2 proximity"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The extracted conversion efficiencies assume that the spin diffusion model, using the two spin lifetimes measured from other electrodes, completely describes what happens in the graphene-WS2 region; if the WS2 strip or its interface adds extra spin loss or an extra conversion channel, the quoted efficiencies would be biased.","fun_headline_variants_meta":{"raw":{"variants":["Electric field switches spin conversion in graphene/WS2","Gate-tunable spin Hall and galvanic effects in graphene/WS2","Room-temp spin conversion tuned by gate in graphene/WS2","Gate-controlled spin conversion in graphene via WS2 proximity"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001205,"raw_usage":{"total_tokens":4971,"prompt_tokens":958,"completion_tokens":4013,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":574,"completion_tokens_details":{"reasoning_tokens":3942}},"tokens_in":574,"tokens_out":4013,"duration_ms":33792,"temperature":1.0,"reasoning_tokens":3942,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T11:55:04.956300+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Make devices with different WS2 strip widths and check that the extracted conversion lengths stay the same; if they vary, the single-channel diffusion model is missing physics. Alternatively, test Onsager reciprocity explicitly by swapping the injection and detection contacts and comparing the two measured voltages.","supporting_citations":[{"cited_title":"A., Sierra, J","cited_arxiv_id":null,"evidence_quote":"Establishes the strongly anisotropic spin relaxation in graphene-WS2 that the present analysis uses to fix the in-plane and out-of-plane spin lifetimes."},{"cited_title":"& Fabian, J","cited_arxiv_id":null,"evidence_quote":"Provides the theoretical spin texture and band structure for graphene on TMDCs that motivates coexistence of spin Hall and spin galvanic effects."},{"cited_title":"H., Cummings, A.W., & Roche, S","cited_arxiv_id":null,"evidence_quote":"Calculates the spin Hall conductivity in graphene/TMDC heterostructures used to compare against the measured gate and temperature dependence."},{"cited_title":"Optimal charge-to-spin conversion in graphene on transition metal dichalcogenide","cited_arxiv_id":null,"evidence_quote":"Predicts charge-to-spin conversion in graphene on TMDC and is used to benchmark the measured spin galvanic efficiency."},{"cited_title":"Y., Taychatanapat, T., Balakrishnan,J., Koon, G.K.W., Yeo, Y., Lahiri, J., Carvalho, A., Rodin, A","cited_arxiv_id":null,"evidence_quote":"The original report of a spin Hall signal in graphene/WS2 that the paper revisits, noting follow-up work questioned its spin origin."},{"cited_title":"K., Ingla-Ayn´ es, J., Herling, F., Garcia, J","cited_arxiv_id":null,"evidence_quote":"A room-temperature spin Hall effect in graphene/MoS2 that the paper distinguishes from its own signal by operating below the WS2 conduction threshold."},{"cited_title":"& Valenzuela, S.O","cited_arxiv_id":null,"evidence_quote":"Supplies the spin precession-based measurement protocol used to separate the inverse spin Hall and spin galvanic contributions."},{"cited_title":"C., Vaz, D.C., Naganuma, H., Sicoli, G., Attan´ e, J","cited_arxiv_id":null,"evidence_quote":"Gives the heavy-metal spin-to-charge conversion values for Pt, Ta, and W that are used to benchmark the measured efficiencies."}],"review_version":1}