{"id":"264cd36b-7596-4850-a476-55620cf62661","arxiv_id":"2608.11284","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"In Bi-2212 and Bi-2223 cuprates, the pseudogap onset temperature lies distinctly above the superconducting-fluctuation onset temperature across all dopings, indicating the pseudogap is not a consequence of superconducting fluctuations.","lead":"Transport measurements on two families of bismuth-based high-temperature superconductors show that the pseudogap energy gap opens at a temperature well above the temperature where superconducting fluctuations first appear. The result argues that the pseudogap is not simply a precursor of superconductivity, and it points instead to preformed electron pairs forming before they condense into a superconductor.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Tscf is defined against the CVC modified-Kohler baseline, yet that baseline is not independently validated in the pseudogap regime; without higher-field saturation or an AL fit, the T**/Tscf separation may be a baseline-breakdown artifact.","rationale":"The reader's weakest assumption is exactly the load-bearing point I identify: Tscf is an operational quantity whose interpretation as SCF onset depends on the CVC framework and on the absence of other field-sensitive processes. The paper's defense of Tscf via the d(rho)/dT field-difference cross-check is not independent because it assumes the same SCF interpretation of field effects, and the admission that 14 T does not fully suppress SCF removes the most direct confirmation (saturation to a normal-state baseline). This is a correctness risk, not merely an absent error bar, because if the modified-Kohler baseline itself breaks down in the pseudogap regime, the temperature where MR deviates from that baseline could have nothing to do with superconducting fluctuations. The concern is addressable: higher-field studies or quantitative AL/Hikami-Larkin fits would settle it, and the data themselves could be re-analyzed with a threshold sensitivity study. The overdoped near-degeneracy of Tscf and T** (p=0.220) further weakens the 'clearly distinct across all dopings' phrasing. These are revision-level issues rather than reasons to reject, so the CONDITIONAL verdict stands without change.","tokens_in":21124,"tokens_out":8642,"duration_ms":78871,"concrete_test":"Measure MR in pulsed fields up to 45-60 T on optimally doped Bi-2212 (p=0.179) at fixed temperatures between Tscf (~120 K) and T** (~180 K). If the slope of MR versus tan^2theta_H decreases monotonically with field and saturates to the high-T modified-Kohler value, the SCF assignment is confirmed; if the slope remains above baseline or continues to grow, the deviation is not a simple field-suppressed SCF effect. As a cheaper immediate check, vary the 10% threshold in Supplemental Fig. 7 between 5% and 20% and recompute Tscf; if the resulting Tscf interval overlaps T** at p=0.220, the claimed 'clearly distinct' separation fails at the overdoped end.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim (T** distinct from Tscf) rests entirely on Tscf being a true SCF onset. Tscf is defined from the 10% rise of MR/tan^2theta_H above the high-T modified-Kohler value (Supplemental Sec. E) and from the d(rho_ab)/dT 1% field-difference cross-check. Both accept the CVC/FLEX normal-state baseline as the null hypothesis. But the paper's own introduction cites high-field results on Bi-2201, Tl-2201, and LSCO showing that the Fermi-liquid/CVC approach is insufficient for hole-doped cuprates, so the baseline in the pseudogap regime is not independently established. The assertion that MR does not depend on xi_AF (so CDW/xi_AF changes cannot cause the deviation) holds only inside CVC with rho_ab proportional to xi_AF^2 T^2 and R_H proportional to xi_AF^2; those are exactly the relations being tested across the pseudogap. The d(rho)/dT cross-check is not independent: any field-suppressed contribution to conductivity, SCF or not, would reduce d(rho)/dT below the 0 T curve. The paper's final Supplemental paragraph concedes that 14 T does not fully suppress SCF, so the excess MR is never directly saturated to a normal-state baseline or compared quantitatively with an AL/Hikami-Larkin field dependence. Thus the observed deviation could be a breakdown of the modified-Kohler baseline in the pseudogap state rather than SCF; if so, Tscf loses its meaning and the T**/Tscf distinction is not established. The distinction is also narrow at the overdoped end (p=0.220: Tscf ~86-90 K, T**upper=95 K), so the 'clearly distinct across all dopings' claim is least secure precisely where the CVC baseline is most likely to hold.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports in-plane magnetotransport measurements on Bi-2212 and Bi-2223 single crystals across a wide doping range, and combines them with previously reported out-of-plane and spectroscopic data. The authors show that the Hall angle follows cot θ_H ∝ T^2 and that the modified Kohler rule MR ∝ tan^2 θ_H holds down to a doping- and material-dependent temperature T_scf, which they identify as the onset of superconducting fluctuations. The pseudogap onset temperatures T**_upper and T**_lower, extracted from resistivity and its derivative, lie well above T_scf in most of the phase diagram. The central claim is that the pseudogap is clearly distinct from superconducting fluctuations, and the authors suggest that the pseudogap may instead reflect preformed Cooper pairing in the BCS-BEC crossover regime.","tokens_in":21484,"tokens_out":5894,"duration_ms":56614,"significance":"If the central claim holds, the paper provides an important experimental constraint: transport signatures of superconducting fluctuations set in far below the pseudogap onset, making a simple superconducting-fluctuation origin of the strong pseudogap unlikely in Bi-2212 and Bi-2223. The manuscript is data-rich, covers two compounds and multiple dopings, and includes several genuine cross-checks: the T**_upper determination is accompanied by a threshold sensitivity analysis, corroborated by ρ_c minima and by comparison with STS and ARPES, and the two independent estimators of T_scf (modified-Kohler slope and field-dependent dρ_ab/dT) agree with each other. The observation that the modified Kohler collapse persists across T**_upper is a striking empirical result in its own right. However, the identification of the low-temperature MR excess specifically with Aslamazov-Larkin superconducting fluctuations rests on the CVC/FLEX framework, and the thresholds defining T_scf are not tested for sensitivity; the admitted lack of saturation at 14 T leaves the SCF interpretation short of being unambiguous.","major_comments":[{"comment":"T_scf is defined by two hand-chosen thresholds—a 10% rise in MR/tan^2 θ_H above its high-temperature plateau and a 1% deviation between dρ_ab/dT at 0 T and 9 T—and no sensitivity analysis or error bars are reported for either threshold. This is not merely a presentation issue: at the overdoped endpoint Bi-2212 p=0.220, T**_upper ≈ 95 K while T_scf is 86–90 K, so the claimed separation is comparable to plausible threshold-induced shifts. I ask the authors to report T_scf for thresholds such as 5%, 10%, and 15% (and correspondingly for the dρ/dT criterion), to state uncertainties in T_scf, and to show explicitly that the T**-T_scf separation survives across the whole doping range.","section":"Supplemental Sec. E, Figs. 7 and 8"},{"comment":"The identification of the low-temperature MR excess with Aslamazov-Larkin superconducting fluctuations is asserted rather than demonstrated quantitatively. The final Supplemental paragraph concedes that 14 T does not fully suppress SCF, so the excess MR is never saturated against a normal-state baseline, and the field dependence is not compared with AL or Hikami-Larkin predictions. Moreover, the dρ/dT cross-check is not independent: any field-suppressed conductivity correction below T** would reduce dρ_ab/dT at 9 T relative to 0 T in the same qualitative way. Fitting MR(B,T) to a specific SCF field dependence, or at least showing the predicted B/T scaling over an extended range, would convert the coincidence of the two threshold criteria into a genuine identification.","section":"Supplemental Sec. E, final paragraph, and main-text Fig. 3"},{"comment":"The rebuttal to CDW-based alternatives is framework-internal. The statement \"within the CVC framework, the magnetoresistance MR does not depend on ξ_AF\" presupposes the validity of Eqs. (1)-(4) in the pseudogap state, but those relations (ρ_ab ∝ ξ_AF^2 T^2, R_H ∝ ξ_AF^2, MR ∝ ξ_AF^4 B^2/ρ_ab^2) are exactly the CVC predictions whose regime of validity is in question, as the manuscript itself notes in citing high-field work on Bi-2201, Tl-2201, and LSCO (Refs. 22 and 23). An independent validation of the modified-Kohler baseline below T**, for example a demonstration that the MR deviation appears with the same temperature onset for several fields and follows the SCF field dependence, is needed before the concluding paragraph's claim to \"unambiguously demonstrate\" the distinction is justified.","section":"Supplemental Sec. E and Eqs. (1)-(4)"}],"minor_comments":[{"comment":"\"temperture\" is a typo for \"temperature\".","section":"Main text near Fig. 1(a)"},{"comment":"The nominal and actual Pb contents appear inconsistent: Bi-2212 is described as Bi_1.6Pb_0.4Sr_2CaCu_2O_8+δ with nominal composition Bi_1.6Pb_0.6Sr_2CaCu_2O_8+δ, and the same discrepancy appears for the underdoped composition; please clarify which formula corresponds to the crystal actually used.","section":"Supplemental Sec. A"},{"comment":"The linear fit giving 2Δ_0/k_B T**_upper ≈ 5.0 is presented without uncertainties or goodness-of-fit information, and the Δ_0 values are taken from a closely related ARPES paper; adding error bars or a table of individual values would make the scaling claim more robust.","section":"Main text Fig. 4"},{"comment":"The text states that Kohler's rule is satisfied at 130 K and 140 K, but the panel shows many other temperatures; the caption and text should explicitly explain why only those two temperatures collapse onto the conventional Kohler curve, since the visual impression may otherwise confuse readers.","section":"Main text Fig. 3(d)"},{"comment":"Reference [49] contains a typo (\"S, Ideta\" should be \"S. Ideta\"), and an editorial pass over the reference list is recommended.","section":"References"}],"recommendation":"major_revision","confidential_remarks":"The paper is within the journal's scope and the dataset appears valuable. The main risk is not the raw data but the interpretive step that converts a breakdown of the modified-Kohler collapse into the onset of superconducting fluctuations. I would ask the authors to provide the T_scf sensitivity analysis and, if possible, a quantitative comparison with an SCF-specific field dependence; without those, the central claim remains too dependent on the CVC baseline. I do not see grounds for rejection, but the threshold uncertainties and the lack of an independent SCF identification need to be addressed before publication."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"You should know this paper is worth a serious look. It gives the first systematic comparison of pseudogap onset and superconducting-fluctuation onset across doping in Bi-2212 and Bi-2223 using magnetotransport, and it makes a plausible case that the two are distinct. The phase diagrams alone are a useful contribution.\n\nWhat is new and good: the dataset is broad, the samples are well characterized, and the authors cross-check their Tscf with two independent-looking methods—the slope of MR/tan^2θH and the field difference in dρab/dT. The modified Kohler plot collapses across T** in most dopings, and the Hall angle follows T^2 even through the pseudogap, which is a clean empirical statement. They also cross-check T** with c-axis resistivity, and the underdoped Bi-2223 resistivity shows a nice T^2 regime. The paper is honest about several limitations, including the fact that 14 T does not fully suppress SCF.\n\nThe soft spots are concentrated around Tscf. It is defined by a hand-chosen 10% rise in the modified-Kohler slope, with no sensitivity analysis and no error bars. The dρ/dT cross-check is not fully independent: any field-suppressed contribution, SCF or not, would produce a deviation from the zero-field curve. The deeper issue is that the modified-Kohler baseline comes from the CVC/FLEX framework. If that baseline breaks down in the pseudogap state, Tscf loses its meaning. The stress-test worry is therefore legitimate, though I think it is not fatal here. In the underdoped samples the separation is large (T**~200 K, Tscf~110 K), so even a generous uncertainty in Tscf would preserve the distinction. And the two detection methods track each other across doping, which is more than many transport papers do. The overdoped end is where the claim is least secure: at p=0.22 the separation is only about 5–10 K, so the phrase \"clearly distinct across all dopings\" is an overstatement.\n\nThe BCS–BEC interpretation is the weakest part of the paper. The 2Δ0/kBT**≈5.0 scaling is suggestive but relies on self-cited ARPES gap values, and the authors themselves concede that the absence of a chemical-potential shift in ARPES is a problem. Their pinning argument is speculative and should be clearly labeled as such, not folded into the main conclusion.\n\nThese issues are addressable. The core observation—pseudogap and SCF onset are well separated in underdoped Bi-2212 and Bi-2223—likely holds up. The paper deserves peer review, and a good referee should ask for error bars on Tscf, a threshold sensitivity analysis, a quantitative AL or Hikami-Larkin comparison, and a stripped-down conclusion that does not overreach into BCS-BEC. I would bring it to a reading group on cuprate transport; the data and the debate are both instructive.","headline":"A genuinely useful wide-doping transport dataset that probably shows the pseudogap and superconducting fluctuations are distinct, but Tscf needs stronger justification before the conclusion is sold as unambiguous.","tokens_in":22185,"tokens_out":2724,"would_cite":true,"duration_ms":27915,"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":"The paper claims that in Bi-2212 and Bi-2223 single crystals the pseudogap onset temperature is clearly distinct from and well above the superconducting fluctuation onset, ruling out a superconducting-fluctuation origin for the strong…","keywords":["pseudogap","superconducting fluctuations","magnetotransport","modified Kohler's rule","Hall angle","Bi-2212","Bi-2223","BCS-BEC crossover"],"falsifier":"A direct test would be to measure the in-plane magnetoresistance in pulsed fields high enough to reach the upper critical field Bc2 just above Tc; if the slope MR/$tan^{2}$θH saturates to the high-temperature line at temperatures still far below T**, the separate onset is confirmed, whereas if the deviation persists even when superconducting fluctuations are fully suppressed, the interpretation fails. Alternatively, observing a field-induced change in the antiferromagnetic correlation length ξ_AF inside the pseudogap that produces a similar MR deviation would eliminate the uniqueness of the superconducting-fluctuation explanation.","tokens_in":20885,"feed_emoji":"🧲","tokens_out":7599,"duration_ms":59243,"temperature":0.7,"pith_summary":"This paper tries to settle whether the high-temperature pseudogap in copper-oxide superconductors is just a cloud of superconducting fluctuations above Tc. It measures in-plane resistivity, Hall effect, and magnetoresistance in Bi-2212 and Bi-2223 single crystals across a wide doping range. The data show that the temperature Tscf where superconducting fluctuations first appear is well below the pseudogap onset T**, even though the modified Kohler's rule (MR proportional to $tan^{2}$θH) stays valid across T**. The authors conclude that the pseudogap is not produced by superconducting fluctuations and instead may reflect Cooper pairs that form far above the condensation temperature, in the BCS-BEC crossover regime.","feed_headline":"Cuprate pseudogap does not come from superconducting fluctuations","feed_subtitle":"In Bi-2212 and Bi-2223, magnetotransport separates pseudogap onset from fluctuation onset across all dopings.","key_machinery":"The central object is the modified Kohler's rule MR ∝ $tan^{2}$θH (= $ξ_AF^{4}$ $B^{2}$/$ρ_ab^{2}$), derived in the current-vertex-correction (CVC) theory of strongly antiferromagnetically fluctuating Fermi liquids. Because MR is independent of the antiferromagnetic correlation length ξ_AF within this framework, the scaling curve supplies a fixed baseline: as long as data fall on a single MR-vs-$tan^{2}$θH curve, superconducting fluctuations are absent; the temperature where the curve breaks identifies Tscf. The Hall-angle identity cotθH ∝ $T^{2}$ plays the supporting role of showing that the strange-metal transport laws persist across the pseudogap, so the pseudogap does not disrupt the single-scattering-rate phenomenology.","core_discovery":"The central discovery is that the pseudogap and superconducting fluctuations are separate temperature scales in Bi-based cuprates. Using the slope of MR versus $tan^{2}$θH to define Tscf (the point where the slope rises 10% above its high-temperature value), and a 1% deviation of ρab from linear-T (or the minimum of dρab/dT) to define T**, the authors construct doping-dependent phase diagrams for Bi-2212 and Bi-2223 in which T** sits distinctly above Tscf at every doping. They also show that cotθH ∝ $T^{2}$ and MR ∝ $tan^{2}$θH hold across T**, while below Tscf an extra magnetoresistance contribution emerges that they attribute to the Aslamazov-Larkin superconducting fluctuation term. The pairing gap Δ0 from ARPES scales with T** with 2Δ0/kBT** ≈ 5.0, close to the d-wave mean-field value 2Δ0/kBTc ≈ 4.3, which they read as evidence that T** marks pair formation while Tc marks phase coherence.","pith_inferences":["If T** is a pairing temperature and superconductivity in these systems is BCS-BEC crossover-like, then other probes that couple to pairing amplitude (Nernst effect, diamagnetism, THz conductivity) should see fluctuation signals at T** rather than at Tscf, a testable extension.","The distinction may reconcile the Hg-1201 result (conventional Kohler, Fermi liquid) with the Bi-based results: the presence of a structurally flat inner CuO2 plane makes the antiferromagnetic correlation length nearly temperature-independent, so both phenomenologies come from the same CVC framework rather than from different physics.","Extending this analysis to single-layer Bi-2201 and to electron-doped cuprates would test whether the T**/Tscf separation is universal or specific to multi-layer Bi families.","If Tscf marks the onset of Aslamazov-Larkin fluctuations, then measurements at fields exceeding the upper critical field just above Tc should make the MR slope saturate to the high-temperature modified-Kohler line, a prediction that higher-field facilities can check."],"forward_implications":["T** and Tscf are separate lines in the phase diagrams of Bi-2212 and Bi-2223, so any theory that derives the strong pseudogap directly from Gaussian superconducting fluctuations above Tc cannot account for these data.","Because MR/tan^2θH stays constant across T**, the CVC strange-metal description remains valid inside the pseudogap region, meaning the pseudogap does not destroy the spin-fluctuation scattering picture.","The ratio 2Δ0/kBT** ≈ 5.0, matching the d-wave mean-field gap ratio, implies that T** is a pairing temperature rather than an ordering temperature of a competing phase.","The pseudogap region likely represents preformed Cooper pairs that condense at Tc, i.e., BCS-BEC crossover behavior, with pair formation and phase coherence as separate energy scales.","The Fermi-liquid-like behavior seen in Hg-1201 (ρab∝T^2, conventional Kohler's rule) is the same strange-metal phenomenology observed locally in underdoped Bi-2223 when ξ_AF is nearly temperature-independent, unifying seemingly different normal-state behaviors."],"supporting_citations":[{"why":"Supplies the CVC/FLEX theory that derives the modified Kohler's rule MR ∝ tan^2θH and the ρab∝T, RH∝T^-1 laws defining the strange-metal baseline used to locate Tscf.","marker":"[14]"},{"why":"The FLEX+T-matrix calculation attributing anomalous pseudogap transport to superconducting fluctuations; it provides the Aslamazov-Larkin contribution the paper uses to identify Tscf and the hypothesis being ruled out.","marker":"[24]"},{"why":"Defines T** via the minimum of dρab/dT for Pb-doped Bi-2212 and supplies the revised phase diagram, crystals, and methods that this paper extends to Bi-2223.","marker":"[28]"},{"why":"Establish the 1% deviation-from-linear-T criterion for T** and prior comparisons of T** with the superconducting-fluctuation onset in Bi-2212.","marker":"[33, 34]"},{"why":"Reports the ρab∝T^2 behavior and T**/Tpg definition in Hg-1201 that motivates the T** lower determination for underdoped Bi-2223.","marker":"[25]"},{"why":"Shows conventional Kohler's rule in the Hg-1201 pseudogap, providing the contrast case against the modified Kohler scaling used to separate fluctuation and pseudogap regimes.","marker":"[26]"},{"why":"Provides ARPES pairing-gap magnitudes Δ0 for Bi-2223 whose scaling with T** gives 2Δ0/kBT**≈5.0.","marker":"[49]"},{"why":"Gives the d-wave mean-field ratio 2Δ0/kBTc≈4.3 used to interpret T** as a pairing temperature.","marker":"[51]"}],"fun_headline_variants":["Pseudogap and superconducting fluctuations are separate scales in cuprates","Magnetotransport shows distinct onsets for pseudogap and fluctuations","Bi-based cuprates: T** above Tscf at all dopings","Cuprate pseudogap onset distinct from fluctuation onset","Evidence for preformed pairs: pseudogap not from fluctuations"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The whole separation rests on the claim that the low-temperature rise of MR/$tan^{2}$θH is caused by superconducting fluctuations; if that deviation instead comes from a field-sensitive change in the magnetic correlations or from a breakdown of the current-vertex-correction baseline, the distinction between T** and Tscf loses its meaning.","fun_headline_variants_meta":{"raw":{"variants":["Pseudogap and superconducting fluctuations are separate scales in cuprates","Magnetotransport shows distinct onsets for pseudogap and fluctuations","Bi-based cuprates: T** above Tscf at all dopings","Cuprate pseudogap onset distinct from fluctuation onset","Evidence for preformed pairs: pseudogap not from fluctuations"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000306,"raw_usage":{"total_tokens":1770,"prompt_tokens":978,"completion_tokens":792,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":594,"completion_tokens_details":{"reasoning_tokens":700}},"tokens_in":594,"tokens_out":792,"duration_ms":10347,"temperature":1.0,"reasoning_tokens":700,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T14:13:08.129417+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A direct test would be to measure the in-plane magnetoresistance in pulsed fields high enough to reach the upper critical field Bc2 just above Tc; if the slope MR/$tan^{2}$θH saturates to the high-temperature line at temperatures still far below T**, the separate onset is confirmed, whereas if the deviation persists even when superconducting fluctuations are fully suppressed, the interpretation fails. Alternatively, observing a field-induced change in the antiferromagnetic correlation length ξ_AF inside the pseudogap that produces a similar MR deviation would eliminate the uniqueness of the superconducting-fluctuation explanation.","supporting_citations":[{"cited_title":"Kontani, Anomalous transport phenomena in Fermi liquids with strong magnetic fluctuations, Rep","cited_arxiv_id":null,"evidence_quote":"Supplies the CVC/FLEX theory that derives the modified Kohler's rule MR ∝ tan^2θH and the ρab∝T, RH∝T^-1 laws defining the strange-metal baseline used to locate Tscf."},{"cited_title":"Kontani, Nernst coefficient and magnetoresistance in high- Tc superconductors: The role of superconducting fluctuations, Phys","cited_arxiv_id":null,"evidence_quote":"The FLEX+T-matrix calculation attributing anomalous pseudogap transport to superconducting fluctuations; it provides the Aslamazov-Larkin contribution the paper uses to identify Tscf and the hypothesis being ruled out."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Shows conventional Kohler's rule in the Hg-1201 pseudogap, providing the contrast case against the modified Kohler scaling used to separate fluctuation and pseudogap regimes."},{"cited_title":"Won and K","cited_arxiv_id":null,"evidence_quote":"Gives the d-wave mean-field ratio 2Δ0/kBTc≈4.3 used to interpret T** as a pairing temperature."}],"review_version":1}