{"id":"7d492de4-0a43-472d-bfc9-0c2c323ff228","arxiv_id":"1908.08828","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"low","formal_verification":"none","parameter_count":1,"one_line_summary":"Low-temperature penetration-depth measurements show LaPtSi is a conventional dirty s-wave superconductor with a dominant spin-singlet pairing component.","lead":"Physicists measured how deeply magnetic fields penetrate the superconductor LaPtSi at temperatures down to two percent of its transition temperature. The data show a conventional fully gapped superconducting state, weakening the case for exotic topological superconductivity in this material.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Central dirty-s-wave claim rests on an unquantified two-model fit; competing gap models are not tested, so the spin-singlet dominance and non-topological conclusion remain conditional.","rationale":"I read the paper as an empirical report: penetration-depth data on one polycrystalline sample, presented as evidence for fully gapped s-wave pairing and against topological nodal superconductivity. The data themselves and the comparison to the dirty-limit model are reasonable first steps; the dirty condition is independently plausible from ref [22], and the claimed Δ0 near the BCS value is internally consistent. However, the central claim is supported by a single, visually judged exponential fit over a restricted temperature range, and the paper itself flags sample-surface irregularities. The reader already identified the inherited dirty-limit parameters and the possibility of surface masking. I partially agree, and would sharpen the conditionality: the missing quantitative model comparison is what prevents the claim from being accepted as established. Because the issues are addressable by a re-analysis of the same data, the verdict remains CONDITIONAL rather than moving to reject or unverified.","tokens_in":5897,"tokens_out":9505,"duration_ms":105529,"concrete_test":"Digitize the Δλ(T) data in Fig. 1 for T < 0.5Tc and perform weighted least-squares fits to Eq. (1), Eq. (2), the full BCS local dirty integral, and a power-law Δλ = A T^n (with and without an exponential low-temperature term), computing AIC/BIC for each. Repeat the comparison over T < 0.2Tc. Also report the 95% confidence interval for Δ0 from the dirty fit. If a power-law or two-gap model is within ΔBIC < 2 of Eq. (2), or the Δ0 interval does not include 1.76kBTc, the claimed dirty s-wave assignment and the spin-singlet dominance conclusion would need revision.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's key inference is that the flattening of Δλ(T) below 0.2Tc (Fig. 1) plus the better visual fit of Eq. (2) over Eq. (1) establishes dirty s-wave pairing with Δ0 = 1.73kBTc, hence a dominant singlet component. The load-bearing step is the model comparison: only the two asymptotic expressions in Eqs. (1)-(2) are fitted, and only visually; no uncertainties, no full BCS integral, and no competing nodal or two-gap model are reported. A fully gapped exponential is not uniquely s-wave: a small second gap, impurity-filled nodes, or a power-law contribution can also produce an apparent saturation over 0.02-0.2Tc. Additionally, Eq. (2) is justified by l = 43 Å and ξ(0) = 338 Å from ref [22], not by measurements on this polycrystalline sample; if this sample's mean free path differs, the dirty-limit formula and the fitted Δ0 lose their basis. The further step to 'spin-singlet component highly dominant' is not a direct consequence of a nodeless λ(T): a moderate triplet admixture can leave the gap fully gapped, so a quantitative bound is missing.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports magnetic penetration depth measurements on polycrystalline noncentrosymmetric LaPtSi down to 0.02 Tc. The authors observe that the low-temperature penetration depth flattens below about 0.2 Tc, fit the data to clean and dirty local s-wave exponential formulas, and conclude that the dirty s-wave model describes the data better, yielding a zero-temperature gap Δ0 = 1.73 kBTc. They interpret this as evidence that the spin-singlet component of the mixed pairing state is highly dominant and that LaPtSi is not a candidate for time-reversal invariant nodal topological superconductivity. A survey of noncentrosymmetric superconductors is used to argue that unconventional behavior requires proximity to magnetic instability rather than strong antisymmetric spin-orbit coupling alone.","tokens_in":6189,"tokens_out":3770,"duration_ms":42103,"significance":"If the central claim is correct, the paper provides useful evidence that strong antisymmetric spin-orbit coupling does not by itself drive unconventional pairing, and it strengthens the empirical pattern that magnetic correlations are the common ingredient in noncentrosymmetric superconductors with nodal gaps. The measurement itself is significant because the penetration depth is taken to an unusually low reduced temperature, and the saturation of Δλ(T) below 0.2 Tc is a genuine qualitative indicator of a nodeless gap. The fitted Δ0 close to the BCS value is also suggestive. However, the key inference depends on model-comparison and parameter-estimation steps that are not quantitatively documented, so the headline conclusion outruns the presented analysis.","major_comments":[{"comment":"The identification of dirty s-wave pairing rests on a visual comparison of Eq. (1) and Eq. (2), with no fit statistics, residuals, or parameter uncertainties. The reported Δ0 = 1.73 kBTc is given without an error bar, so the reader cannot assess whether the clean model is statistically excluded or whether a single exponential with a different prefactor would also describe the data. Please report χ² values or an equivalent goodness-of-fit criterion, uncertainties on Δ0, and residual plots, and preferably fit the full local BCS and dirty-limit expressions rather than only the low-temperature asymptotes up to 0.5 Tc.","section":"Section 3, Eq. (2)"},{"comment":"The flattening below 0.2 Tc is strong qualitative evidence for a nodeless gap, but it does not uniquely select isotropic s-wave pairing: a fully gapped two-gap state, a small second gap, or nodes partly filled by impurity scattering can also produce a saturating curve over the measured range. Since the paper's central claim is that the spin-singlet component is 'highly dominant,' the authors should fit at least one nodal model and one two-gap model to the same data and report which model is preferred. A nodeless gap alone does not constrain the singlet/triplet ratio, because a fully gapped mixed-parity state can still contain a substantial triplet admixture.","section":"Section 3, Fig. 1"},{"comment":"The dirty-limit justification uses l = 43 Å and ξ(0) = 338 Å taken from ref [22], a different sample, rather than from measurements on the polycrystalline sample used here. The exponential dirty-limit form in Eq. (2) and the extracted Δ0 depend on this assumption. Please either characterize the mean free path of the measured sample (e.g., from resistivity or upper critical field) or demonstrate that the fitted Δ0 and the s-wave versus nodal distinction are robust over a plausible range of l/ξ0. Without this, the dirty-limit assignment and the s-wave conclusion remain conditional.","section":"Section 3, text following Eq. (2)"}],"minor_comments":[{"comment":"The verb 'cutted' should be 'cut', and 'reaffirming' in the results section is a typographical error.","section":"Sample preparation, Section 2"},{"comment":"Equation (1) is ambiguous: the square-root sign should be shown with explicit parentheses, e.g., (πΔ0/(2kBT))^{1/2}, to distinguish the quoted prefactor from √(πΔ0)/(2kBT).","section":"Eq. (1)"},{"comment":"The statement that the error bars are the size of the dots needs a numerical indication of the measurement uncertainty; as printed, no error bars are visible in the figure.","section":"Fig. 1 caption"},{"comment":"The selection criterion for Table I is stated as ESO/kBTc > 500 or a nodal gap, but Y2C3 is included despite a reported ratio below 10; the criterion should be stated more precisely so the table entries are self-consistent.","section":"Table I"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a short experimental report whose main contribution is a very low-temperature penetration depth measurement. The refereeing process should ask the authors to provide the underlying fit data and quantitative model comparison, since the main headline is currently supported mainly by a visual assessment. The paper is not fatally flawed, but the load-bearing inference needs to be backed by statistical and model-selection analysis."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"First penetration-depth run on LaPtSi reaching 0.02Tc. The flattening below 0.2Tc is strong qualitative evidence for a full gap, and the dirty-limit exponential fit gives Δ0 = 1.73 kBTc, close to BCS. That part should survive scrutiny. The paper also usefully assembles the growing list of noncentrosymmetric superconductors where strong ASOC coexists with conventional s-wave pairing, and correctly notes the correlation with magnetism rather than ASOC for unconventional gaps.\n\nWhat's genuinely new: previous specific heat only reached 0.67Tc; this measurement nails the low-temperature behavior. The result extends the empirical pattern and effectively removes LaPtSi from the nodal topological SC shortlist, at least for the zero-field time-reversal invariant case.\n\nSoft spots: the s-wave assignment is based on a visual comparison of two asymptotic formulas, Eqs. (1) and (2), with no uncertainties, no residuals, and no quantitative comparison to competing models. A fully gapped exponential is not unique to dirty s-wave: a two-gap or a nodal gap with strong impurity scattering can also mimic saturation in this range. The dirty-limit parameters come from a previous report on a different sample; if this polycrystal's mean free path differs, Eq. (2) loses its justification. Also, 'dominant spin-singlet component' is an interpretive step beyond a nodeless penetration depth: moderate triplet admixtures can leave the gap fully open. I wouldn't call these fatal; the qualitative conclusion is probably right. But the paper overstates its certainty in the abstract, and a referee should ask for fit uncertainties and at least one alternative-gap fit. Minor: no data file is supplied, so the fits cannot be rechecked independently.\n\nCitation pattern is fine; the comparison table is useful and the relevant prior work is cited.\n\nWho this is for: people working on noncentrosymmetric superconductors and on how much gap-structure information penetration depth can carry. I'd send it to peer review, but with a request for a more quantitative analysis. I would bring it to a reading group as an example of a solid measurement with an overreaching interpretation.","headline":"First deep-penetration-depth data for LaPtSi show a robust fully gapped response, but the dirty-s-wave and spin-singlet-dominance conclusions are more qualitative than the abstract claims.","tokens_in":6691,"tokens_out":2943,"would_cite":true,"duration_ms":29676,"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":"Strong spin-orbit coupling fails to break s-wave pairing in LaPtSi.","keywords":["noncentrosymmetric superconductors","antisymmetric spin-orbit coupling","magnetic penetration depth","dirty s-wave superconductivity","BCS energy gap","topological superconductivity","LaPtSi"],"falsifier":"Measure the penetration depth, specific heat, or thermal conductivity of a cleaner LaPtSi single crystal below 0.02 Tc: a power-law tail, such as $\\Delta\\lambda \\propto T^n$ with $n < 3$, or a finite residual linear term in the specific heat would show that the supposed s-wave gap actually has nodes or that the dirty s-wave fit is masking another gap structure.","tokens_in":5730,"feed_emoji":"🧲","tokens_out":6096,"duration_ms":53915,"temperature":0.7,"pith_summary":"The paper sets out to settle the gap structure of the noncentrosymmetric superconductor LaPtSi, a material whose antisymmetric spin-orbit coupling is among the strongest known relative to its critical temperature. By measuring the magnetic penetration depth down to 0.02 Tc, the authors find that the data flatten below about 0.2 Tc and that a dirty local s-wave model fits the low-temperature tail with a zero-temperature gap Δ0 = 1.73 kBTc, close to the BCS value of 1.76. They conclude that the spin-singlet component of the mixed pairing state is highly dominant, that a strong antisymmetric spin-orbit coupling alone does not generate nodes or unconventional behavior, and that LaPtSi is not a promising host for time-reversal-invariant nodal topological superconductivity.","feed_headline":"Strong spin-orbit coupling fails to break s-wave pairing in LaPtSi","feed_subtitle":"Penetration depth down to 0.02 Tc fits a BCS gap of 1.73 kBTc, ruling out nodal topological pairing.","key_machinery":"The central object is the magnetic penetration depth $\\Delta\\lambda(T)$ measured with a 13.5 MHz tunnel diode oscillator down to about 50 mK. The argument is carried by comparing two functional fits to the low-temperature data: the clean local BCS model, $\\Delta\\lambda \\propto \\sqrt{\\pi\\Delta_0/2k_B T}\\,\\exp(-\\Delta_0/k_B T)$, and the dirty local s-wave model, $\\Delta\\lambda \\propto \\exp(-\\Delta_0/k_B T)$. The dirty model is applicable because previous work reports a mean free path $l = 43$ Å and a coherence length $\\xi_{GL}(0) = 338$ Å, placing the material deep in the dirty limit. The dirty fit's success, with $\\Delta_0 = 1.73\\,k_B T_c$, is what converts a flat low-temperature tail into the claim of a fully gapped spin-singlet state.","core_discovery":"The central claim is that LaPtSi is a conventional, fully gapped s-wave superconductor in the dirty limit. The evidence is the exponential low-temperature penetration depth that flattens below 0.2 Tc, fitted by the dirty local s-wave expression $\\Delta\\lambda(T) \\propto \\exp(-\\Delta_0/k_B T)$ up to 0.5 Tc with $\\Delta_0 = 1.73\\,k_B T_c$, nearly identical to the BCS ratio. Because the gap shows no zeros, the authors argue that the spin-singlet component of the parity-mixed pairing state dominates. They then generalize: among noncentrosymmetric superconductors, unconventional gap structures appear only in materials with magnetic order or proximity to a magnetic instability, not simply in those with very large $E_{\\mathrm{SO}}/k_B T_c$. Consequently the fully gapped state excludes LaPtSi as a candidate for time-reversal-invariant nodal topological superconductivity, although field-induced topological phases remain possible.","pith_inferences":["A sharper test of the s-wave assignment would be thermal-conductivity or specific-heat measurements below 0.1 Tc on a cleaner sample; a residual linear term or power-law tail would indicate that surface irregularities are masking nodes.","The paper's comparative pattern suggests a testable prediction: noncentrosymmetric superconductors without a magnetic instability should remain fully gapped, so measuring gap structures in the remaining uncharacterized strong-ASOC materials would check this directly.","If the dirty s-wave picture holds, the most interesting remaining topological route for LaPtSi is the field-induced phase; angle-resolved or field-dependent penetration-depth measurements could look for that transition."],"forward_implications":["If the claim is correct, LaPtSi should show no residual low-temperature quasiparticle excitations: thermal conductivity, specific heat, and penetration depth should all continue to follow activated exponential forms below 0.2 Tc.","The compound can be removed from the short list of candidates for time-reversal-invariant nodal topological superconductivity among noncentrosymmetric materials.","The comparative pattern implies that searches for unconventional gap structures in noncentrosymmetric superconductors should weight magnetic proximity more heavily than the ratio $E_{\\mathrm{SO}}/k_B T_c$.","The earlier specific-heat data that suggested BCS-like behavior down to 0.67 Tc are confirmed and extended into the true low-temperature regime.","A fully gapped state leaves open the field-induced topological route discussed in the paper, which does not require the spin-triplet component to be large."],"supporting_citations":[{"why":"Introduces the ASOC-induced mixing of spin-singlet and spin-triplet pairing in noncentrosymmetric superconductors, the theoretical context being tested.","marker":"[1]"},{"why":"Supplies the tunnel-diode oscillator method used to measure the penetration depth.","marker":"[2]"},{"why":"Reports the fully gapped, s-wave behavior of the closely related noncentrosymmetric compound LaPt3Si, the comparison case for the claim that strong ASOC can coexist with conventional pairing.","marker":"[5]"},{"why":"Provides the sample, Tc = 3.7 K, the ASOC band splitting of 130–255 meV, and earlier specific-heat data hinting at BCS-like behavior; the paper extends this measurement to 0.02 Tc.","marker":"[21]"},{"why":"Gives the coherence length and mean free path that place LaPtSi in the dirty limit, justifying the dirty s-wave model.","marker":"[22]"},{"why":"Supplies the dirty local s-wave formula $\\Delta\\lambda \\propto \\exp(-\\Delta_0/k_B T)$ used for the fit.","marker":"[23]"},{"why":"Provides the contrasting line-node penetration-depth result in Li2Pt3B, used in the discussion of when strong ASOC does produce unconventional gaps.","marker":"[4]"}],"fun_headline_variants":["Strong spin-orbit coupling fails to disrupt s-wave pairing in LaPtSi","LaPtSi: conventional s-wave despite strong spin-orbit coupling","No unconventional pairing in LaPtSi despite strong spin-orbit","LaPtSi gap study rules out topological superconductivity","Strong spin-orbit coupling doesn't break s-wave in LaPtSi"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The argument depends on the low-temperature flattening being intrinsic bulk behavior rather than a surface artifact, and on the previously reported dirty-limit parameters applying to this particular sample.","fun_headline_variants_meta":{"raw":{"variants":["Strong spin-orbit coupling fails to disrupt s-wave pairing in LaPtSi","LaPtSi: conventional s-wave despite strong spin-orbit coupling","No unconventional pairing in LaPtSi despite strong spin-orbit","LaPtSi gap study rules out topological superconductivity","Strong spin-orbit coupling doesn't break s-wave in LaPtSi"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000809,"raw_usage":{"total_tokens":3515,"prompt_tokens":877,"completion_tokens":2638,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":493,"completion_tokens_details":{"reasoning_tokens":2548}},"tokens_in":493,"tokens_out":2638,"duration_ms":17762,"temperature":1.0,"reasoning_tokens":2548,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T11:27:55.474075+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the penetration depth, specific heat, or thermal conductivity of a cleaner LaPtSi single crystal below 0.02 Tc: a power-law tail, such as $\\Delta\\lambda \\propto T^n$ with $n < 3$, or a finite residual linear term in the specific heat would show that the supposed s-wave gap actually has nodes or that the dirty s-wave fit is masking another gap structure.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Introduces the ASOC-induced mixing of spin-singlet and spin-triplet pairing in noncentrosymmetric superconductors, the theoretical context being tested."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the tunnel-diode oscillator method used to measure the penetration depth."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Reports the fully gapped, s-wave behavior of the closely related noncentrosymmetric compound LaPt3Si, the comparison case for the claim that strong ASOC can coexist with conventional pairing."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the sample, Tc = 3.7 K, the ASOC band splitting of 130–255 meV, and earlier specific-heat data hinting at BCS-like behavior; the paper extends this measurement to 0.02 Tc."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Gives the coherence length and mean free path that place LaPtSi in the dirty limit, justifying the dirty s-wave model."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the dirty local s-wave formula $\\Delta\\lambda \\propto \\exp(-\\Delta_0/k_B T)$ used for the fit."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the contrasting line-node penetration-depth result in Li2Pt3B, used in the discussion of when strong ASOC does produce unconventional gaps."}],"review_version":1}