{"id":"24a83048-9147-467d-8b94-2e0841f1f0d4","arxiv_id":"2506.17730","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":8.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"An intrinsic, room-temperature nonlinear planar Hall effect is observed in TaIrTe4 and quantitatively matched by first-principles calculations of the Berry-connection polarizability dipole susceptibility.","lead":"This paper reports the first observation of an intrinsic nonlinear planar Hall effect in the topological semimetal TaIrTe4, where a Hall voltage grows with the square of the driving current and linearly with an in-plane magnetic field. The measured response matches first-principles calculations of a band-geometric quantity, the Berry-connection polarizability dipole susceptibility, and persists up to room temperature.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Intercept η identified as intrinsic BCP susceptibility rests on untested assumptions of temperature independence and absence of contaminating artifacts.","rationale":"The reader's weakest assumption correctly identifies the intercept η as the crucial link between experiment and the intrinsic BCP susceptibility. I agree that any unremoved temperature-independent artifact would contaminate the intercept. However, I would sharpen the concern: even in the absence of extrinsic artifacts, the intrinsic BCP dipole susceptibility itself may be temperature-dependent over 100–300 K, so the linear extrapolation to zero conductivity may not yield the zero-temperature intrinsic value used in the DFT comparison. This is a separate and arguably more fundamental issue than the presence of artifacts, though both are captured under the broad umbrella of 'the intercept must be purely intrinsic and constant.' The paper's strengths—the E²B scaling, the C2v angular dependence, the sign and magnitude match for two independent tensor components, and the orbital mechanism—are genuine and support the intrinsic interpretation, but they do not independently verify the intercept. The proposed split-window refit directly tests whether η is stable, which is the minimal check needed to justify the central claim. Since the reader's verdict is already CONDITIONAL and this concern reinforces that condition rather than overturning the paper, the verdict should remain unchanged.","tokens_in":11221,"tokens_out":4344,"duration_ms":47950,"concrete_test":"Refit the data in Fig. 4(c,d) using only the 100–200 K subset and only the 200–300 K subset, and compute the intercepts η1 and η2 with propagated uncertainties; if the two intercepts differ by more than the combined uncertainty, η is not a temperature-independent intrinsic constant and the central claim is weakened.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim—that the observed NPHE is intrinsic—hinges entirely on the identification of the zero-conductivity intercept η in Eq. (4) with the intrinsic BCP dipole susceptibility Υ. This identification requires two conditions that are not demonstrated. First, the scaling χ = ξσ + η must be exactly linear over the entire 100–300 K range; the paper reports an 'almost perfect linear scaling' but provides no residuals, error bars, or statistical tests, so the extrapolation to σ = 0 is unverified. If the true relation contains a curvature term, the fitted intercept is biased. Second, η must be temperature-independent and represent the intrinsic contribution at zero temperature. However, the BCP dipole susceptibility (Eq. 1) is a Fermi-surface quantity weighted by f0′; in a semimetal with near-degenerate bands, thermal smearing over 100–300 K can substantially change Υ. If Υ(T) varies, the intercept from a linear χ–σ fit is a weighted average over the measured temperature window, not the zero-temperature value, and the agreement with zero-temperature DFT (χ1^int = 2.40e-4, χ2^int = -1.73e-4) could be coincidental. Moreover, any temperature-independent extrinsic second-harmonic contribution—from contact asymmetry, a magnetic-field-dependent background, or electrode misalignment—would directly enter η. The paper rules out some geometric and frequency-dependent artifacts, but it does not exclude all such contributions. Because the angular dependence and E²B scaling are consistent with several nonlinear transport mechanisms, the intercept is the only evidence that isolates the intrinsic BCP mechanism, making this the load-bearing assumption of the paper.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports the experimental discovery of a nonlinear planar Hall effect (NPHE) in the type-II Weyl semimetal TaIrTe4, with a Hall current scaling as E^2 B and an angular dependence consistent with the C2v crystal symmetry. The effect persists up to room temperature. By measuring the NPHE conductivity as a function of longitudinal conductivity over 100–300 K, the authors observe an approximately linear scaling chi = xi sigma + eta and identify the zero-conductivity intercept eta with the intrinsic Berry-connection polarizability (BCP) dipole susceptibility. First-principles calculations yield Upsilon_yxxy = 2.40e-4 and Upsilon_yxxx = -1.73e-4 m T^-1 V^-2, matching the experimental intercepts (eta_1 = 2.8e-4, eta_2 = -1.6e-4) in sign and magnitude. The calculations also show a dominant orbital contribution to the BCP dipole susceptibility, beyond the conventional spin Zeeman mechanism.","tokens_in":11515,"tokens_out":4541,"duration_ms":47258,"significance":"If the identification of the intercept eta with the intrinsic BCP dipole susceptibility is correct, this is the first observation of intrinsic NPHE and the first experimental probe of the BCP dipole susceptibility, achieving room-temperature operation. The paper is strengthened by its frequency-independence tests (Supplemental Note 3), out-of-plane field checks (Supplemental Note 4), multiple device geometries (Hall bar and circular disk), consistency across three devices (Table S1), and parameter-free DFT calculations that reproduce the signs and approximate magnitudes of both independent tensor components. The claims would be transformative for nonlinear transport in polar/chiral semimetals. However, the central claim rests on a scaling intercept that is assumed to be temperature-independent and purely intrinsic, which is not yet fully established, as detailed in the major comments.","major_comments":[{"comment":"The identification of the zero-conductivity intercept eta with the intrinsic BCP dipole susceptibility assumes that chi = xi sigma + eta holds with a temperature-independent eta over the entire 100–300 K range. The intrinsic susceptibility defined in Eq. (1) contains the Fermi-Dirac derivative f0', so in a semimetal with small-gap regions near the Fermi level it can itself vary substantially with temperature. The paper does not compute Upsilon(T) over 100–300 K nor provide an argument for its constancy. If Upsilon varies with temperature, the fitted intercept is a weighted average over the temperature window, and the agreement with zero-temperature DFT (chi1^int = 2.40e-4, chi2^int = -1.73e-4) could be coincidental. Please provide the temperature dependence of the calculated Upsilon, or an explicit theoretical justification that it is constant, and show how the experimental intercept relates to the zero-temperature value.","section":"Fig. 4 and Eq. (4)"},{"comment":"The 'almost perfect linear scaling' is not supported by statistical evidence: the figures show no error bars, residuals, or the number of independent temperature points, and the statement in the text that uncertainties are smaller than the symbol size is not a substitute for a quantitative fit. The extrapolation to sigma = 0 is a two-parameter linear fit over a limited temperature range; any small curvature (e.g., a term proportional to sigma^2) would bias the intercept. Please report the raw data, the fit parameters with uncertainties, and a statistical test comparing the linear form with an alternative functional form (for example, chi = xi sigma + eta + gamma sigma^2).","section":"Fig. 4(c,d) and Eq. (4)"},{"comment":"The extraction of eta as an intrinsic contribution assumes that all temperature-independent second-harmonic artifacts are either absent or completely removed. The paper subtracts a magnetic-field-independent background and rules out electrode misalignment and some geometric effects through temperature-dependent measurements (Supplemental Notes 5 and 9), but it does not quantitatively exclude temperature-independent contributions from contact asymmetry, thermoelectric voltages, or magnetic-field-dependent contact resistances. Because the intercept is the sole evidence for the intrinsic claim, a control experiment (e.g., reversing current and voltage contacts, or measuring a centrosymmetric reference sample with identical contact geometry) is needed to confirm that no such artifact contributes to eta.","section":"Eq. (4) and angular dependence section"}],"minor_comments":[{"comment":"The indices in the definition of the BCP dipole appear inconsistent: the integrand is written with v_y G_xy and v_y G_yy, but the component D_yxx should involve G_xx or a combination that is not clearly defined. Please check the index structure and ensure the notation matches the derivation in the Supplemental Material.","section":"Eq. (1)"},{"comment":"The fit of beta versus theta depends on the resistivity anisotropy ratio r (determined to be about 0.24), but the sensitivity of the extracted chi_1 and chi_2 to the uncertainty in r is not discussed. Please provide an estimate of how errors in r propagate to the NPHE conductivity values.","section":"Fig. 3(c)"},{"comment":"The conclusion states that the measurements 'allow us to probe the BCP dipole susceptibility,' but the experimental access is indirect (through the scaling intercept). Consider softening this wording to reflect the model-dependent identification.","section":"Conclusion"}],"recommendation":"major_revision","confidential_remarks":"This is a potentially important experimental result, but the central claim of intrinsic NPHE critically depends on the temperature-independence and artifact-free nature of the intercept in Eq. (4). The manuscript would be substantially strengthened by (i) reporting error bars and raw data for the scaling fits, (ii) computing the temperature dependence of Upsilon and showing it is negligible, and (iii) adding a control experiment that isolates contact or thermoelectric artifacts. I do not see the concerns as fatal, but they need to be addressed before publication in a high-impact journal."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nYou should know this is the first credible claim of an intrinsic nonlinear planar Hall effect, at room temperature, with a quantitative theory match. The experiment is clean in its main scalings: the second-harmonic Hall voltage is sinusoidal in field angle, linear in B, quadratic in I, frequency independent, and the out-of-plane field controls are done. The measured response, around 10^-4 m T^-1 V^-2, is two orders above the extrinsic NPHE in SrIrO3, and the intercept from the chi-sigma plot gives eta1 = 2.8e-4 and eta2 = -1.6e-4 against DFT values of 2.40e-4 and -1.73e-4 with the correct signs. The orbital-mechanism decomposition, where the orbital contribution outweighs the spin contribution by an order of magnitude, is new and physically interesting. The prior theory, Ref. [14], is by overlapping authors, but the DFT here is an independent parameter-free computation, not a fit to the experiment, so I do not see circularity.\n\nThe soft spot is exactly the one flagged in the stress-test: the intrinsic part is isolated as the intercept of a two-parameter linear fit over 100-300 K. No residuals or error bars are shown, and the 'almost perfect linear scaling' is asserted. If the chi-sigma relation has curvature, or if any temperature-independent second-harmonic background from contact asymmetry, thermoelectric effects, or surface contributions survives the subtraction, it goes directly into eta. Also, the BCP dipole susceptibility is a Fermi-surface quantity; over 100-300 K, thermal broadening in a semimetal can change it, so the fitted intercept may be a weighted average over the temperature window rather than the zero-temperature value, and the agreement with zero-T DFT could be partly fortuitous. The misalignment check is delegated to the Supplemental Material, and raw data are not in the main text.\n\nNone of this kills the claim, but it makes it conditional. A referee should ask for the raw chi versus sigma data with fit residuals, error bars on eta, a control device with deliberately misaligned contacts, and a calculation of the susceptibility's temperature dependence over the measured range. If those come out clean, this is a strong result: a room-temperature probe of BCP dipole susceptibility and a route to intrinsic nonlinear transport in a broad material class.\n\nI would send it to peer review rather than desk reject. The right outcome is probably publication after the intercept identification is nailed down. Worth discussing in our group.\n\nBest","headline":"First credible intrinsic NPHE claim with strong scaling checks; the load-bearing intercept needs more supporting data before it is fully trusted.","tokens_in":12094,"tokens_out":2196,"would_cite":true,"duration_ms":23690,"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 reports the first experimental observation of the intrinsic nonlinear planar Hall effect in the topological semimetal TaIrTe$_4$, where a second-harmonic Hall voltage quadratic in the driving current and linear in an in-plane…","keywords":["nonlinear planar Hall effect","Berry-connection polarizability","BCP dipole susceptibility","TaIrTe4","topological semimetal","orbital magnetic moment","second-harmonic transport","quantum geometry"],"falsifier":"Measure the same second-harmonic Hall response on TaIrTe4 flakes of different thicknesses (e.g., 30 nm vs 10 nm) and with different surface terminations: a bulk intrinsic intercept $\\eta$ must remain constant, while a surface or contact artifact would vary with the surface-to-volume ratio.","tokens_in":11014,"feed_emoji":"🧲","tokens_out":11599,"duration_ms":107484,"temperature":0.7,"pith_summary":"This paper tries to establish that the topological semimetal TaIrTe$_4$ shows an intrinsic nonlinear planar Hall effect: a Hall voltage that scales with the square of the driving current and linearly with an in-plane magnetic field, with the coefficient set by a band-geometric quantity, the Berry-connection polarizability dipole susceptibility, rather than by scattering. The signal persists at room temperature, reaching about $10^{-4}\\ \\mathrm{m\\,T^{-1}\\,V^{-2}}$, roughly two orders of magnitude above the extrinsic signals reported earlier. By fitting the conductivity to $\\chi = \\xi\\sigma + \\eta$ over a temperature sweep, the authors separate a temperature-linear extrinsic term from a temperature-independent intercept $\\eta$ and show that its two independent components match first-principles values ($2.40\\times10^{-4}$ and $-1.73\\times10^{-4}\\ \\mathrm{m\\,T^{-1}\\,V^{-2}}$) in magnitude and sign. The calculations also identify a previously unnoticed orbital-moment coupling to the magnetic field that dominates the response and does not require spin-orbit coupling.","feed_headline":"Room-temperature Hall effect traces to band geometry, not scattering","feed_subtitle":"In TaIrTe4, the nonlinear Hall conductivity matches quantum-geometry calculations at 300 K, making an intrinsic band property readable in…","key_machinery":"The load-bearing object is the Berry-connection polarizability (BCP) dipole susceptibility, a fourth-rank tensor $\\Upsilon_{abcd}$ defined by $\\mathfrak{D}_{abc} = \\Upsilon_{abcd} B_d$, where $\\mathfrak{D}$ is the Fermi-surface integral of the BCP dipole and the BCP tensor itself is $G_{ab} = 2\\,\\mathrm{Re}\\sum_{n\\neq m} v_a^{mn}v_b^{nm}/(\\varepsilon_m-\\varepsilon_n)^3$. It converts an in-plane magnetic field into a field-induced BCP dipole, and the resulting second-order current is $j_a^{(2)} = \\Upsilon_{abcd} E_b E_c B_d$. On the experimental side, the linear scaling $\\chi = \\xi\\sigma + \\eta$ is the tool that separates the intrinsic intercept $\\eta$, identified with $\\Upsilon$, from the extrinsic slope $\\xi$.","core_discovery":"The central discovery is the first observation of the intrinsic nonlinear planar Hall effect in a nonmagnetic crystal. In TaIrTe$_4$, the second-harmonic transverse voltage obeys $j_a^{(2)} = \\Upsilon_{abcd} E_b E_c B_d$, with $\\Upsilon$ the BCP dipole susceptibility, and shows the angular dependence dictated by $C_{2v}$ symmetry: the signal's phase $\\beta$ differs from the current angle $\\theta$, the amplitude peaks when current is along the $y$ axis, and both magnetic-field and current scalings are linear as required. The temperature sweep produces an almost perfect linear scaling $\\chi = \\xi\\sigma + \\eta$, and the intercepts $\\eta_1 = 2.8\\times10^{-4}$ and $\\eta_2 = -1.6\\times10^{-4}\\ \\mathrm{m\\,T^{-1}\\,V^{-2}}$ agree with the first-principles components $\\chi_1^{\\mathrm{int}} = 2.40\\times10^{-4}$ and $\\chi_2^{\\mathrm{int}} = -1.73\\times10^{-4}$, including the opposite signs. A further claim is that the orbital moment of Bloch electrons, not just the spin Zeeman coupling, generates most of $\\Upsilon$ — for one component the orbital part is an order of magnitude larger — and this orbital channel works even without spin-orbit coupling.","pith_inferences":["The authors do not test this, but their $\\chi$–$\\sigma$ intercept protocol could be applied to existing NPHE data in Bi$_2$Se$_3$, SrIrO$_3$, and Te: a nonzero temperature-independent intercept there would reveal an intrinsic component hidden under the dominant extrinsic $\\sim\\tau^2$ response.","A thickness-dependence experiment would settle the surface-artifact question: if $\\eta$ is the bulk BCP susceptibility, it should be identical in 30-nm and 40-nm flakes and after different surface treatments, whereas any surface background would scale with surface-to-volume ratio.","Because the orbital channel needs no spin-orbit coupling, two-dimensional polar materials made of light atoms are natural testbeds; a null intercept in such a material, despite a symmetry-allowed tensor, would force a re-examination of the orbital mechanism.","Searching for correlations between the intercept and Fermi-level position, for example by chemical doping or electrostatic gating in a material where the carrier density is tunable, would test the k-space localization of $\\Upsilon$ near small-gap regions."],"forward_implications":["The intrinsic NPHE is a material property, so any TaIrTe$_4$ crystal with the same band structure should reproduce the intercept $\\eta$ regardless of device geometry or contact quality.","Because all polar and chiral crystal classes support the intrinsic NPHE, the measurement protocol transfers to high-symmetry point groups such as $C_{6v}$, $D_6$, $T$, and $O$, where other second- and third-order nonlinear Hall effects are symmetry-forbidden.","The dominant orbital mechanism operates without spin-orbit coupling, so sizable intrinsic NPHE should appear in light-element polar and chiral materials.","The room-temperature magnitude of $\\chi_1 \\sim 10^{-4}\\ \\mathrm{m\\,T^{-1}\\,V^{-2}}$ supports nonlinear device functions such as wireless rectification and energy harvesting at ambient conditions."],"supporting_citations":[{"why":"Establishes the extrinsic NPHE baseline in Bi2Se3, WTe2, and SrTiO3 that this paper must distinguish from the intrinsic effect.","marker":"[13]"},{"why":"Gives the symmetry prediction that all polar and chiral crystal classes host an intrinsic NPHE, and supplies the tensor form used in the analysis.","marker":"[14]"},{"why":"Defines the Berry-connection polarizability dipole and the intrinsic second-order Hall conductivity that the NPHE susceptibility extends.","marker":"[4]"},{"why":"Reports the room-temperature nonlinear response in SrIrO3 used here as the comparison showing the TaIrTe4 signal is two orders of magnitude larger.","marker":"[17]"},{"why":"Provides the theory showing extrinsic mechanisms can produce linear $\\chi$–$\\sigma$ scaling, the alternative that the intercept analysis must exclude.","marker":"[29]"},{"why":"Prior TaIrTe4 demonstration of room-temperature nonlinear Hall and wireless rectification, supporting both the surface-background attribution and the device applications.","marker":"[28]"},{"why":"Theoretical treatment of bilinear magneto-electric resistance used to argue that previously observed planar-Hall-type signals are extrinsic.","marker":"[21]"}],"fun_headline_variants":["Intrinsic nonlinear planar Hall lives to 300 K in TaIrTe4","Quantum geometry sets nonlinear Hall signal up to 300 K in TaIrTe4","First intrinsic nonlinear planar Hall at room temperature in TaIrTe4","Orbital effect leads nonlinear planar Hall in TaIrTe4 at 300 K"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The intercept $\\eta$ in the empirical scaling $\\chi = \\xi\\sigma + \\eta$ is assumed to contain only the intrinsic BCP-dipole-susceptibility contribution; any temperature-independent artifact, such as contact asymmetry, surface background, thermoelectric offset, or electrode misalignment, that survives the background subtraction would be mistaken for the intrinsic effect.","fun_headline_variants_meta":{"raw":{"variants":["Intrinsic nonlinear planar Hall lives to 300 K in TaIrTe4","Quantum geometry sets nonlinear Hall signal up to 300 K in TaIrTe4","First intrinsic nonlinear planar Hall at room temperature in TaIrTe4","Orbital effect leads nonlinear planar Hall in TaIrTe4 at 300 K"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000985,"raw_usage":{"total_tokens":4208,"prompt_tokens":1004,"completion_tokens":3204,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":620,"completion_tokens_details":{"reasoning_tokens":3120}},"tokens_in":620,"tokens_out":3204,"duration_ms":22684,"temperature":1.0,"reasoning_tokens":3120,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T19:02:09.186658+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the same second-harmonic Hall response on TaIrTe4 flakes of different thicknesses (e.g., 30 nm vs 10 nm) and with different surface terminations: a bulk intrinsic intercept $\\eta$ must remain constant, while a surface or contact artifact would vary with the surface-to-volume ratio.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Establishes the extrinsic NPHE baseline in Bi2Se3, WTe2, and SrTiO3 that this paper must distinguish from the intrinsic effect."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Gives the symmetry prediction that all polar and chiral crystal classes host an intrinsic NPHE, and supplies the tensor form used in the analysis."},{"cited_title":"Geometrical Quantum Materials","cited_arxiv_id":null,"evidence_quote":"Defines the Berry-connection polarizability dipole and the intrinsic second-order Hall conductivity that the NPHE susceptibility extends."},{"cited_title":"Yokouchi, Y","cited_arxiv_id":null,"evidence_quote":"Reports the room-temperature nonlinear response in SrIrO3 used here as the comparison showing the TaIrTe4 signal is two orders of magnitude larger."},{"cited_title":"Kumar, C.-H","cited_arxiv_id":null,"evidence_quote":"Provides the theory showing extrinsic mechanisms can produce linear $\\chi$–$\\sigma$ scaling, the alternative that the intercept analysis must exclude."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Prior TaIrTe4 demonstration of room-temperature nonlinear Hall and wireless rectification, supporting both the surface-background attribution and the device applications."},{"cited_title":"Suárez-Rodríguez, B","cited_arxiv_id":null,"evidence_quote":"Theoretical treatment of bilinear magneto-electric resistance used to argue that previously observed planar-Hall-type signals are extrinsic."}],"review_version":1}