{"id":"95bda3cc-9c8b-4387-b4bf-50bffe8a4bd5","arxiv_id":"2412.09785","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Trilayer graphene with a SnS layer shows a measurable gate-tunable spin Hall effect up to room temperature, peaking near the charge neutrality point.","lead":"This paper reports the first experimental observation of a gate-tunable spin Hall effect in trilayer graphene placed in contact with tin sulfide, a layered semiconductor. The result adds group-IV monochalcogenides to the small set of materials that can give graphene the spin-orbit coupling it needs for spintronic devices.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Quantitative theta_SH and lambda_SCI rest on the untested equality of D_s between pristine and SnS-covered trilayer graphene; the antisymmetric Hanle fit likely cannot constrain D_s_prox independently, so the headline values may shift if this assumption is relaxed.","rationale":"Agree with the reader that the quantitative extraction is the weakest point. I make the concern sharper: the equality assumption is not merely untested; it is likely violated because the paper's own Fig. 2d shows a temperature-dependent CNP shift due to charge transfer, so the doping in the proximitized region differs from the pristine arms. Since lambda_s_prox is a factor ~6.6 shorter than lambda_s_pristine, the spin current transported into the Hall cross dominates the signal, making the fit sensitive to D_s_prox. If D_s_prox is free, theta_SH and tau_s_prox are partially degenerate, so the reported values are not robust. However, the existence of an antisymmetric Hanle signal, its gate dependence, and reproducibility in Sample 2 are not called into question by this concern; hence the conditional verdict stands and no change to the reader's verdict is needed.","tokens_in":14363,"tokens_out":7318,"duration_ms":87021,"concrete_test":"Re-analyze the antisymmetric Hanle datasets underlying Fig. 5(a) (plus SI Note 3 and Sample 2) with D_s in the SnS-covered segment as a free parameter instead of fixing it to the pristine-region value, and report the resulting theta_SH and lambda_SCI together with confidence contours. If theta_SH moves outside the quoted ±0.05% error bar (or lambda_SCI outside ±0.16 nm), the quantitative central claim fails as stated. An independent cross-check would be a device with two FM electrodes straddling the SnS-covered cross, allowing a direct Hanle measurement of D_s in the proximitized region.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central quantitative claims (theta_SH=0.47±0.05% at 100 K, lambda_SCI=0.97±0.16 nm) are extracted in SI Note 5 by fitting the antisymmetric Hanle signal with Eq. (10). In the final paragraph the authors write: 'since the CNP is the same for the pristine and proximitized regions, we assume the spin diffusion coefficients for the proximitized region and the pristine region to be equal.' This is the single assumption that makes the fit identifiable, but it is both unverified and questionable: the main text reports a temperature-dependent CNP shift in the SnS-covered region attributable to charge transfer (Fig. 2d), which implies the local carrier density, and hence D_s, in the proximitized region need not match the pristine arms. The fitted lambda_s_prox is only ~330 nm versus 2190 nm in pristine graphene, so the spin current profile through the cross is dominated by the proximitized segment; D_s_prox enters that profile directly. With D_s_prox fixed, the fit can separately return theta_SH and tau_s_prox; with D_s_prox free, the two are partially degenerate because both change the amplitude of R_SCI. Thus the quoted theta_SH and lambda_SCI, and their gate and temperature trends, carry an unquantified systematic error that could be as large as the reported values.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports the first experimental observation of the spin Hall effect in trilayer graphene proximitized with SnS, a group-IV monochalcogenide. The authors fabricate a lateral spin-valve device with a graphene Hall bar partially covered by SnS, measure nonlocal spin precession, and extract a gate-tunable spin Hall angle that peaks near the charge neutrality point and persists up to 300 K. The reported values include theta_SH = 0.47±0.05% at 100 K and 0.10±0.01% at 300 K (Vg = 0 V), and an SCI efficiency lambda_SCI of 0.97±0.16 nm at 100 K (Vg = 10 V). The quantitative extraction uses a standard Bloch-equation model of the antisymmetric Hanle signal, with the spin diffusion coefficient in the SnS-covered region assumed equal to that in pristine graphene.","tokens_in":14701,"tokens_out":3323,"duration_ms":35521,"significance":"If the quantitative claims hold, this work expands the family of materials that can induce strong spin-orbit coupling in graphene to group-IV monochalcogenides, a new and potentially tunable class. The observation of a gate-tunable SHE up to room temperature, with a competitive spin-charge interconversion efficiency, is of clear interest for graphene-based spintronics. The paper includes two devices (one as a reproducibility check), temperature-dependent and gate-dependent data, and a transparent description of the fitting model. The antisymmetric Hanle signal is a standard and reliable signature of spin-to-charge conversion. However, the central quantitative results (theta_SH, lambda_s^prox, lambda_SCI) rest on an explicit assumption about equal spin diffusion coefficients in pristine and proximitized regions, and the reported error bars only reflect fitting uncertainty, not this model uncertainty.","major_comments":[{"comment":"The assumption that D_s is equal in pristine and SnS-proximitized trilayer graphene, introduced to reduce the number of fitting parameters, is load-bearing for all quantitative results reported in Figs. 5(b)-(d). The justification given is that the CNP is the same in both regions, but Fig. 2(d) shows a temperature-dependent CNP shift attributed to charge transfer between SnS and graphene, indicating that the local carrier density in the proximitized region need not match that in the pristine arms. Since D_s depends on carrier density, the equality is questionable. Because lambda_s_prox is fitted to be roughly 330 nm versus 2190 nm in pristine graphene, the spin-current profile is dominated by the proximitized segment, and the extracted theta_SH and tau_s_prox are partially degenerate if D_s_prox is allowed to vary. The authors should either provide an independent measurement or estimate of D_s_prox, or perform a sensitivity analysis showing how theta_SH and lambda_SCI change under a plausible range of D_s_prox values. Without this, the quoted values and their gate/temperature trends carry an unquantified systematic error that could be comparable to the reported differences.","section":"Eq. (10) and Fig. 5(c)"},{"comment":"The reported large reduction of the spin diffusion length in the proximitized region (from 2190±20 nm to 330±90 nm at 100 K) is a central result, but it is obtained under the same equal-D_s assumption. The value of D_s is taken from fits to pristine graphene, and the spin lifetime in the proximitized region is then adjusted to match the antisymmetric Hanle amplitude and line shape. If the true D_s in the SnS-covered region is smaller (e.g., due to enhanced disorder or charge inhomogeneity), the fitted lambda_s_prox would change, and so would the spin Hall angle via the normalization in Eq. (10). The error bars in Fig. 5(c) and (d) are fitting errors only. I recommend the authors explicitly state the systematic uncertainty from this assumption, or, ideally, fit the antisymmetric Hanle data with D_s_prox as a free parameter using a dedicated experiment or a degenerate-branch analysis to bound the impact on theta_SH and lambda_SCI.","section":null},{"comment":"The claim that the gate dependence of theta_SH peaks near the CNP is a key physics statement, but the peak position and even its existence could be affected by the D_s assumption if D_s_prox varies with gate voltage differently than D_s of the pristine region. The pristine spin transport data in Fig. 3(d) show that lambda_s is nearly gate-independent, but the local carrier density in the proximitized region is shifted relative to the pristine arms due to charge transfer (Fig. 2(d)). Since D_s is related to the carrier density, using the pristine D_s at each applied Vg for the proximitized region maps the gate axis incorrectly if the CNPs differ. The authors should discuss this offset or analyze the data using the local density calibration from the proximitized-region resistance (Fig. 2(d)).","section":null}],"minor_comments":[{"comment":"In the caption of Fig. S4, the antiparallel configuration is labeled as R_NL^P in both instances; the red line should presumably be R_NL^AP.","section":null},{"comment":"The authors state that the SCI signal amplitude decreases with temperature and attribute this to weakening of the proximity effect. However, spin injection and detection efficiencies also vary with temperature, and the model does not separate these contributions. A sentence noting that the temperature trend of the raw amplitude is not solely a proximity-effect measure would improve clarity.","section":null},{"comment":"The 300 K value of lambda_SCI, 0.35±0.41 nm, is consistent with zero within error. The text should explicitly acknowledge this large relative uncertainty when comparing to literature values.","section":null},{"comment":"The device fabrication section mentions that the SnS flake is stamped onto graphene before nanopatterning. The possibility that the Hall-bar etching or subsequent processing modifies the SnS/graphene interface is not discussed; a comment about the cleanliness of the interface would be useful.","section":null}],"recommendation":"major_revision","confidential_remarks":"The manuscript is well-written and the experimental data are of high quality, with a standard and appropriate measurement methodology. The main concern is the unverified equal-D_s assumption in the quantitative extraction of the spin Hall angle and spin diffusion length. This is not a fatal flaw, as the antisymmetric Hanle signal itself and its gate/temperature trends are likely robust, but the specific numerical values and their error bars do not yet account for the model uncertainty. If the authors can provide a sensitivity analysis or even a rough independent estimate of D_s in the proximitized region, the paper would be suitable for publication. I recommend major revision, not rejection."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Dear Colleague,\n\nThe headline: this is the first experimental report of a spin Hall effect in graphene proximitized with a group-IV monochalcogenide (SnS). The qualitative claim—a gate-tunable antisymmetric Hanle signal that survives to 300 K and appears in a second device—looks solid. The measurement protocol is the established nonlocal spin-precession method used by the same community for graphene/TMD and graphene/oxide devices, and the analysis follows the standard Bloch-equation fitting. That is a legitimate extension to a new material class, and the paper includes careful device characterization (Raman, transport, AFM).\n\nWhat the paper does well: the antisymmetric Hanle curves are clean, the signal scales sensibly with gate voltage and temperature, and the authors explicitly state their key assumption in SI Note 5. The comparison of SCI efficiency with heavy metals and graphene/oxide systems is useful context.\n\nThe soft spot is the quantitative extraction. The fitted theta_SH and lambda_s_prox rest on the assumption that D_s is the same in pristine and SnS-covered trilayer graphene. That assumption is unverified and somewhat questionable—the main text itself shows a temperature-dependent CNP shift in the proximitized region attributed to charge transfer, suggesting the local carrier density (and therefore D_s) may differ from the pristine arms. With D_s_prox fixed, the fit can return theta_SH and tau_s_prox; if D_s_prox is allowed to float, those two parameters become partially degenerate because both affect the amplitude of R_SCI. So the quoted values (theta_SH ~0.47% at 100 K, lambda_SCI ~0.97 nm) carry an unquantified systematic error that could be as large as the reported numbers. I would not call this circularity—the antisymmetric signal is real and the gate dependence is a measured input—but the headline numbers are model-dependent. Also, raw data and code are only available on request, which makes it harder for a referee to independently test the fitting robustness.\n\nThe central existence claim likely holds. For a serious referee, the question is whether the quantitative SOC parameters survive a relaxation of the D_s equality. I would send it to review, with a request for a robustness analysis (e.g., fits with D_s_prox free, or a bound on how much the extracted values shift). The paper is for the graphene spintronics community; it deserves a careful referee, not a desk rejection.\n\nBest,\n[Name]","headline":"First experimental SHE in graphene/SnS looks real, but the quoted theta_SH and lambda_SCI are hostage to an untested D_s equality assumption.","tokens_in":15236,"tokens_out":2635,"would_cite":true,"duration_ms":26905,"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":"This paper reports the first experimental observation of a gate-tunable spin Hall effect in trilayer graphene proximitized with SnS, a group-IV monochalcogenide, with the spin Hall angle peaking near the charge neutrality point and…","keywords":["spin Hall effect","graphene","tin sulfide","group-IV monochalcogenide","proximity-induced spin-orbit coupling","spin-charge interconversion","Hanle spin precession","van der Waals heterostructure"],"falsifier":"A control experiment with a non-spin-orbit spacer between graphene and SnS should kill the antisymmetric Hanle signal; more quantitatively, placing two ferromagnetic electrodes entirely on the SnS-covered region to measure Hanle precession only there would give a direct value of the spin diffusion coefficient $D_s$, checking the equality assumption and re-deriving the spin Hall angle without it.","tokens_in":14198,"feed_emoji":"🧲","tokens_out":5469,"duration_ms":51165,"temperature":0.7,"pith_summary":"Spin-based electronics needs a material that can both carry spins over long distances and convert them into charge signals. This paper reports that placing trilayer graphene under a flake of tin sulfide (SnS), a layered group-IV monochalcogenide, imprints enough spin-orbit coupling on the graphene to produce a spin Hall effect that is electrically tunable and survives up to 300 K. Spin Hall angles extracted from nonlocal spin-precession measurements reach about 0.47% at 100 K near the charge neutrality point, and the spin-charge interconversion efficiency reaches about 0.97 nm at 100 K. If correct, the result adds a new family of materials to the short list of proximity sources that can functionalize graphene for spintronics.","feed_headline":"Tin sulfide coating gives graphene a gate-tunable spin Hall effect","feed_subtitle":"Proximity to SnS imprints spin-orbit coupling on trilayer graphene, converting spin current to charge at up to 300 K.","key_machinery":"The experimental workhorse is the nonlocal spin-precession (Hanle) measurement in a lateral spin valve: a ferromagnetic injector sends a spin current down a pristine graphene arm into a SnS-covered Hall cross, where out-of-plane spin components generated by precession in an in-plane magnetic field are converted into a transverse charge voltage. The antisymmetric part of the Hanle signal, obtained by reversing the injector magnetization and antisymmetrizing in field, isolates the (inverse) spin Hall effect from Rashba-Edelstein and magnetoresistance contributions. Fitting the signal to the one-dimensional Bloch equation with boundary conditions for spin injection, backflow, and contact-resistance pulling yields the spin Hall angle and the spin lifetime of the proximitized region.","core_discovery":"The paper's central claim is that a van der Waals heterostructure of trilayer graphene and tin sulfide exhibits the spin Hall effect as a result of proximity-induced spin-orbit coupling, demonstrated for the first time in a group-IV monochalcogenide/graphene system. Using nonlocal Hanle spin-precession measurements, the authors isolate an antisymmetric spin signal that is the signature of spin-to-charge conversion by the inverse spin Hall effect, and they quantify a spin Hall angle that decreases from $0.47\\pm 0.05\\%$ at 100 K to $0.10\\pm 0.01\\%$ at 300 K at zero gate voltage, with a maximum near the charge neutrality point. The spin diffusion length of the proximitized graphene is shortened by the added spin-orbit coupling, and the spin-charge interconversion efficiency $\\theta_{\\mathrm{SH}}\\lambda_s^{\\mathrm{prox}}$ reaches $0.97\\pm 0.16$ nm at 100 K, comparable to graphene/metal-oxide systems and larger than typical heavy-metal values.","pith_inferences":["If the mechanism is the same intrinsic spin Hall conductivity that theory predicts for graphene/TMD systems, then varying the chalcogen or metal in the group-IV monochalcogenide layer (e.g., SnSe, GeS) should systematically change the spin Hall angle with atomic spin-orbit strength; this is a testable prediction not made in the paper.","Because SnS is also ferroelectric, a natural extension is to ask whether switching the SnS polarization reconfigures the proximity spin-orbit coupling and therefore the spin Hall angle; the present data do not address this.","The quantitative values of $\\theta_{\\mathrm{SH}}$ and $\\lambda_{\\mathrm{SCI}}$ rest on the assumption that the spin diffusion coefficient is unchanged by proximity; if a future measurement contradicts that, the reported magnitudes will shift even though the existence and gate dependence of the antisymmetric Hanle signal should survive."],"forward_implications":["Group-IV monochalcogenides become a viable second family of two-dimensional materials, alongside transition-metal dichalcogenides and metal oxides, for proximity-inducing spin-orbit coupling in graphene.","Spin-to-charge conversion in the SnS/graphene system remains measurable at 300 K, so room-temperature spintronic devices based on proximity-functionalized graphene are within reach.","The spin Hall angle peaks near the charge neutrality point and is tuned by the back gate, giving an electrical knob for spin-charge interconversion efficiency in a single device.","Even with the added spin-orbit coupling, the proximitized channel keeps a spin diffusion length of hundreds of nanometers, so the system retains long-distance spin transport while gaining spin manipulation.","The measured spin-charge interconversion efficiency around 0.97 nm at 100 K is higher than in heavy metals such as Pt and W, suggesting the heterostructure could serve as an efficient spin-charge converter."],"supporting_citations":[{"why":"Supplies the theoretical prediction that group-IV monochalcogenides can transfer spin-orbit coupling to graphene through the proximity effect.","marker":"[44]"},{"why":"Provides the experimental demonstration of the spin Hall effect in graphene/WSe2 and the nonlocal spin-precession method used here.","marker":"[14]"},{"why":"Establishes the graphene/BiOx spin Hall effect and supplies a direct comparison for the extracted spin-charge interconversion efficiency.","marker":"[15]"},{"why":"Shows gate-tunable spin Hall effect in graphene/TMD heterostructures, giving the CNP-peaking behavior this paper mirrors.","marker":"[18]"},{"why":"Predicts that spin Hall conductivity in proximitized graphene peaks near the charge neutrality point, which the experimental gate dependence is compared against.","marker":"[25]"},{"why":"Presents graphene/CuOx spin-charge interconversion, another method and efficiency comparison point.","marker":"[30]"},{"why":"Supports the choice of trilayer graphene by reporting longer spin diffusion lengths than monolayer graphene on SiO2/Si.","marker":"[47]"},{"why":"Provides the spin-charge interconversion efficiency of Pt as a heavy-metal benchmark.","marker":"[51]"},{"why":"Provides the spin-charge interconversion efficiency of W as a heavy-metal benchmark.","marker":"[52]"}],"fun_headline_variants":["SnS proximity grants trilayer graphene a gate-tunable spin Hall effect","Gate-tunable spin Hall effect emerges in trilayer graphene/SnS heterostructure","Trilayer graphene with SnS shows electrically controlled spin Hall effect","Spin Hall effect in trilayer graphene controlled by gate via SnS proximity","Proximity to SnS yields gate-tunable spin Hall effect in trilayer graphene"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The numbers for the spin Hall angle and spin diffusion length in the SnS-covered graphene are extracted assuming the spin diffusion coefficient is unchanged by the SnS proximity and that the charge neutrality point is identical in pristine and covered regions, a simplification adopted to keep the fitting manageable.","fun_headline_variants_meta":{"raw":{"variants":["SnS proximity grants trilayer graphene a gate-tunable spin Hall effect","Gate-tunable spin Hall effect emerges in trilayer graphene/SnS heterostructure","Trilayer graphene with SnS shows electrically controlled spin Hall effect","Spin Hall effect in trilayer graphene controlled by gate via SnS proximity","Proximity to SnS yields gate-tunable spin Hall effect in trilayer graphene"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000686,"raw_usage":{"total_tokens":3130,"prompt_tokens":984,"completion_tokens":2146,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":600,"completion_tokens_details":{"reasoning_tokens":2042}},"tokens_in":600,"tokens_out":2146,"duration_ms":16048,"temperature":1.0,"reasoning_tokens":2042,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T16:43:37.479506+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A control experiment with a non-spin-orbit spacer between graphene and SnS should kill the antisymmetric Hanle signal; more quantitatively, placing two ferromagnetic electrodes entirely on the SnS-covered region to measure Hanle precession only there would give a direct value of the spin diffusion coefficient $D_s$, checking the equality assumption and re-deriving the spin Hall angle without it.","supporting_citations":[{"cited_title":"Giant asymmetric proximity-induced spin-orbit coupling in twisted graphene/SnTe heterostructure","cited_arxiv_id":"2402.09045","evidence_quote":"Supplies the theoretical prediction that group-IV monochalcogenides can transfer spin-orbit coupling to graphene through the proximity effect."},{"cited_title":"Herling, C","cited_arxiv_id":null,"evidence_quote":"Provides the experimental demonstration of the spin Hall effect in graphene/WSe2 and the nonlocal spin-precession method used here."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Establishes the graphene/BiOx spin Hall effect and supplies a direct comparison for the extracted spin-charge interconversion efficiency."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Shows gate-tunable spin Hall effect in graphene/TMD heterostructures, giving the CNP-peaking behavior this paper mirrors."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Predicts that spin Hall conductivity in proximitized graphene peaks near the charge neutrality point, which the experimental gate dependence is compared against."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Presents graphene/CuOx spin-charge interconversion, another method and efficiency comparison point."},{"cited_title":"Maassen, F","cited_arxiv_id":null,"evidence_quote":"Supports the choice of trilayer graphene by reporting longer spin diffusion lengths than monolayer graphene on SiO2/Si."},{"cited_title":"Rojas-Sá nchez, N","cited_arxiv_id":null,"evidence_quote":"Provides the spin-charge interconversion efficiency of Pt as a heavy-metal benchmark."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the spin-charge interconversion efficiency of W as a heavy-metal benchmark."}],"review_version":1}