{"id":"b1656757-5c5f-4595-9c74-c8983f0940ca","arxiv_id":"2504.15450","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"In the topologically trivial semimetal ScSb, a Nernst power factor of 35 x 10^-4 W/m/K^2 and a figure of merit of 28 x 10^-4 K^-1 are measured at 12 K and 14 T, matching topological semimetals.","lead":"ScSb, a simple semimetal with no topological band features, produces a Nernst signal as strong as those seen in topological semimetals used for thermomagnetic cooling. The result suggests that costly topological band engineering may not be needed to achieve efficient Nernst-based refrigeration.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Conclusion overreaches: comparable Nernst values in trivial ScSb do not imply that Berry curvature is not the primary contributor in topological semimetals, since their high values could arise from a different mechanism.","rationale":"The reader correctly identified the mechanistic attribution (phonon drag) as unsupported, and that concern is real: the paper provides only inferential evidence for phonon drag in ScSb. However, the more load-bearing issue for the central claim is the cross-material inference about Berry curvature. The paper's headline conclusion goes beyond the data because it assumes that comparable PF_N/z_N values in a trivial semimetal imply the same mechanism dominates in topological semimetals. That is a logical gap independent of whether ScSb's own mechanism is phonon drag or some other normal effect. The proposed concrete test would quantitatively assess whether the normal two-band model can account for the Nernst signal in a representative topological semimetal, thereby determining whether the comparison substantiates the conclusion. Since the experimental values in ScSb remain valid and the missing support is in the interpretation, the reader's CONDITIONAL verdict is appropriate; no change to the verdict is needed.","tokens_in":9758,"tokens_out":8400,"duration_ms":74936,"concrete_test":"Select one topological semimetal from Fig. 3 (e.g., Cd3As2) and compute the normal two-band Nernst coefficient using the carrier densities and mobilities reported for that material, either from the semiclassical two-band equations analogous to Eqs. (1)-(2) with experimentally constrained S_e and S_h, or from the low-field ambipolar Nernst expression. Compare the calculated Sxy to the measured peak value at the same temperature and magnetic field. If the normal mechanism reproduces the measured Nernst signal within roughly 20%, the paper's conclusion is supported; if it falls short by more than a factor of about 2, the topological semimetal's signal requires an additional anomalous contribution, and the claim that Berry curvature is not primary in those materials is refuted. This check directly tests whether the comparison between ScSb and topological semimetals is mechanism-controlled.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central experimental finding—Nernst thermopower of 47 uV/K at 12 K and 14 T, PF_N ~35e-4 W/m/K^2, and z_N ~28e-4 K^-1—is internally consistent and supported by Hall, ARPES, and DFT. The load-bearing weakness is the interpretive leap in the Conclusions: because ScSb is topologically trivial and its PF_N/z_N are comparable to values in topological semimetals, the authors conclude that Berry-curvature-driven anomalous Nernst is not the primary contributor in those topological semimetals. This does not follow. ScSb's large Nernst is attributed to electron-hole compensation plus phonon drag (Section III), but no evidence shows that the topological semimetals referenced in Fig. 3 (Cd3As2, ZrTe5, PtSn4, TbPtBi, etc.) achieve their peaks via the same normal mechanisms. Their Nernst peaks may occur at different temperatures and fields and may be dominated by the anomalous term; the ScSb comparison only shows that a trivial semimetal can also have large values, which is an existence statement, not a decomposition of the topological semimetal signal. The phonon-drag attribution for ScSb itself is also inferred only from the Sxx peak and the temperature dependence, without a quantitative model. Even if the phonon-drag explanation is correct, the paper does not demonstrate that phonon drag is present at comparable strength in Cd3As2 and other materials. Thus the strongest conclusion (Berry curvature not primary) is underdetermined by the data.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports transport, ARPES, and DFT measurements on the cubic semimetal ScSb, which the authors classify as topologically trivial. They observe a Nernst thermopower Sxy of about 47 µV/K at 12 K and 14 T, a Nernst power factor PFN of about 35 × 10^-4 W m^-1 K^-2, and a Nernst figure of merit zN of about 28 × 10^-4 K^-1. The authors attribute the large Nernst signal to nearly perfect electron-hole compensation, supported by two-carrier fits to Hall and longitudinal conductivity, ARPES Fermi-surface mapping, and DFT band-structure calculations. They compare PFN and zN with values reported for topological semimetals and argue that, since ScSb is topologically trivial and reaches comparable values, the Berry-curvature-induced anomalous Nernst effect is not the primary contributor to the enhanced thermomagnetic performance of topological semimetals.","tokens_in":10101,"tokens_out":3357,"duration_ms":31930,"significance":"If the conclusions are properly bounded, this is a valuable experimental contribution. It demonstrates that a topologically trivial, well-compensated semimetal can exhibit Nernst power factors and figures of merit in the range previously associated with topological semimetals, which is relevant for thermomagnetic cooling applications and for understanding the role of band topology in the Nernst effect. The paper's strengths include the internal consistency among transport, ARPES, and DFT; the direct measurement of Sxy, PFN, and zN rather than derivation from a fitted model; and the explicit comparison of Fermi-surface shapes and carrier densities. The main weakness is that the broad conclusion about Berry curvature in topological semimetals goes beyond what the data can establish, and the phonon-drag attribution is not quantitatively tested. With a revised interpretation and proper uncertainty propagation, the paper would be a solid and useful addition to the field.","major_comments":[{"comment":"The concluding statement that \"the anomalous Nernst effect driven by Berry curvature in topological semimetals is not the primary contributor to their enhanced thermomagnetic performance\" is not supported by the presented data. The experiment shows that one trivial compensated semimetal can have PFN and zN values comparable to those of several topological semimetals, but it does not decompose the Nernst signal in Cd3As2, ZrTe5, PtSn4, or TbPtBi into normal and anomalous contributions. Those materials may achieve their peaks at different temperatures and fields and may be dominated by different mechanisms. I recommend reframing the conclusion as an existence statement: a topologically trivial semimetal can exhibit comparably large Nernst response, so large PFN/zN alone does not prove a Berry-curvature origin. A quantitative comparison of the normal Nernst contribution in the topological reference materials would be needed to support the stronger claim.","section":"Section IV (Conclusions)"},{"comment":"The attribution of the 12 K Nernst peak to phonon drag is inferred only from the coincident peak in Sxx and from the temperature dependence, without a quantitative model or a control experiment. The text states that \"the same mechanism also boosts the Nernst thermopower,\" but no estimate of the phonon-drag contribution to Sxy is given, and alternatives such as ambipolar diffusion or inelastic scattering are not discussed. Since the mechanistic explanation of the large Nernst effect in ScSb depends on this attribution, the claim in the Conclusions that the values \"arise from well compensated electron and hole carriers ... and a strong phonon drag effect\" needs either quantitative support or a more cautious phrasing.","section":"Section III (Results and discussion, around Fig. 1 and Fig. 2)"},{"comment":"No uncertainties are reported for Sxy, σyy, κxx, PFN, or zN, so the statement that the ScSb values are \"comparable\" to those of topological semimetals is not quantitatively established. The only stated uncertainties are the ±5% errors on carrier densities and mobilities from the two-carrier fit. Given that the central claim rests on a quantitative comparison with literature values, I request error propagation from the measured quantities into PFN and zN, and, if possible, error bars in Fig. 3 so that the reader can assess whether the differences among materials are significant.","section":"Section III (PFN and zN definitions, Fig. 3)"}],"minor_comments":[{"comment":"There is a typo in \"in a a JEOL JSM-7600F scanning electron microscope\" and another in \"exhange-correlation functional.\" Please correct these.","section":"Section II (Methods)"},{"comment":"The comparison in Fig. 3 lists maximum PFN and zN values for each material but does not specify the temperature and magnetic field at which each maximum was obtained. Since the peaks occur at different conditions, adding this information to the caption or text would make the comparison more meaningful.","section":"Section III (Fig. 3 and surrounding text)"},{"comment":"The statement that \"the value of Sxx is nearly zero down to T = 100 K\" is vague; please provide the approximate magnitude or a zoomed inset so that the reader can verify the near-zero behavior.","section":"Section III (Fig. 1c)"},{"comment":"The notation \"it is evident\" appears as \"its evident\" in the text; please correct the grammar.","section":"Section III (ARPES paragraph)"}],"recommendation":"major_revision","confidential_remarks":"The experimental core of the paper is sound and the measured values are likely to be of interest to the thermomagnetic community. However, the Conclusions overreach by claiming that the results rule out Berry curvature as the primary contributor in topological semimetals, which the data cannot establish. The revision should temper this claim and add quantitative error propagation. I believe the paper can become acceptable after these changes, so I recommend major revision rather than rejection."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nThe thing to know up front: the experimental Nernst data on ScSb are new and look solid, but the paper's headline conclusion overreaches. The measured Sxy peak near 47 uV/K at 12 K and 14 T, PF_N ~ 35e-4 W/m/K^2, and z_N ~ 28e-4 K^-1 are internally consistent and, as far as I can tell, not reported before for this material. Those numbers deserve attention.\n\nWhat the paper does well: the authors characterize the material thoroughly. The two-carrier Hall analysis gives nh/ne ~ 1.05, consistent with near-perfect electron-hole compensation. ARPES and DFT agree on the Fermi surface topology: three hole pockets at Gamma and electron pockets at X. The transport features (resistivity plateau, field-induced crossover) fit the standard compensated-semimetal picture. The comparison of PF_N to Seebeck power factors of Bi2Te3 and PbTe is apt and gives context. This is a careful experimental study.\n\nThe soft spot is the concluding claim. Because trivial ScSb shows PF_N and z_N comparable to topological semimetals, the authors say Berry curvature is not the primary contributor to the enhanced thermomagnetic performance of those materials. That does not follow. The ScSb comparison is an existence proof, not a mechanism decomposition. The topological materials in Fig. 3 (Cd3As2, ZrTe5, TbPtBi, etc.) may achieve their peaks through different physical processes, at different temperatures and fields. To conclude that Berry curvature is unimportant, you would need a direct comparative test or a quantitative decomposition of the Nernst signal in at least one of those materials. The paper provides neither.\n\nThe phonon-drag attribution for ScSb itself is also inferred from the Seebeck peak and temperature dependence, not from a quantitative model. It is plausible, but it remains an interpretation. If that attribution is wrong, the mechanistic story for why ScSb is so good would be unsupported, though the measured values would still stand.\n\nMinor but addressable: PF_N and z_N lack error bars, and raw data are not provided. Both should be fixed for a final version.\n\nThis is a solid experimental contribution with one interpretive leap too far. It deserves a serious referee, not a desk rejection. I would send it to review, with the recommendation that the authors either soften the Berry-curvature conclusion or add evidence that directly tests the mechanism in topological semimetals. The measured values and characterization are the real content, and they should see the light of day.","headline":"Solid Nernst measurements on ScSb with a new high-value result, but the Berry-curvature conclusion is a logical leap the data do not support.","tokens_in":10639,"tokens_out":2310,"would_cite":true,"duration_ms":22304,"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":"ScSb, a topologically trivial compensated semimetal, reaches a Nernst thermopower of 47 µV/K at 12 K and 14 T, with PF_N ≈ 35×10⁻⁴ W m⁻¹ K⁻² and z_N ≈ 28×10⁻⁴ K⁻¹, matching topological semimetals; the paper argues topology is thus not…","keywords":["Nernst effect","thermomagnetic refrigeration","electron-hole compensation","phonon drag","semimetal","Nernst power factor","figure of merit","topologically trivial"],"falsifier":"Measure the Nernst thermopower in ScSb samples whose electron-hole ratio is deliberately shifted away from unity by slight Sb deficiency or doping: if the 12 K peak and the large power factor survive, compensation is not the controlling mechanism; a quantitative transport calculation that includes phonon drag and uses the measured carrier densities and mobilities should reproduce the ~$47\\,\\mu\\mathrm{V}/\\mathrm{K}$ peak, and if it cannot, the phonon-drag attribution is unsupported.","tokens_in":9588,"feed_emoji":"🧊","tokens_out":9344,"duration_ms":74530,"temperature":0.7,"pith_summary":"The paper reports that ScSb, a semimetal with ordinary, topologically trivial electronic bands, shows a Nernst thermopower of about $47\\,\\mu\\mathrm{V}/\\mathrm{K}$ at 12 K in a 14 T field. From that signal the authors derive a Nernst power factor $PF_N \\approx 35 \\times 10^{-4}\\,\\mathrm{W\\,m^{-1}\\,K^{-2}}$ and a Nernst figure of merit $z_N \\approx 28 \\times 10^{-4}\\,\\mathrm{K^{-1}}$, values comparable to those of topological semimetals such as Cd$_3$As$_2$, ZrTe$_5$, and TbPtBi. The authors attribute the large signal to near-perfect electron-hole compensation, demonstrated by Hall measurements, angle-resolved photoemission spectroscopy, and density functional theory, combined with phonon drag. The significance is that it challenges the assumption that Berry curvature or nontrivial topology is required for strong thermomagnetic performance.","feed_headline":"Trivial semimetal ScSb matches topological Nernst numbers","feed_subtitle":"Electron-hole balance plus phonon drag yields a Nernst figure of merit of 28×10⁻⁴ K⁻¹ at 12 K.","key_machinery":"The load-bearing objects are the semiclassical two-carrier model, equations (1) and (2) of the paper, which fit the field-dependent longitudinal and Hall conductivities to extract separate hole and electron densities and mobilities; and the measured and calculated Fermi surface showing three nested $\\Gamma$-centered hole pockets and three pairs of $X$-centered electron ellipsoids with no band inversion. The two-carrier model demonstrates near-perfect compensation ($n_h/n_e \\approx 1.05$), and the Fermi-surface maps establish the topologically trivial character. The performance metrics are then built from the measured $S_{xy}$, $\\sigma_{yy}$, and $\\kappa_{xx}$ through $PF_N = S_{xy}^2\\,\\sigma_{yy}$ and $z_N = S_{xy}^2\\,\\sigma_{yy}/\\kappa_{xx}$, with the low thermal conductivity at 12 K (about $1.5\\,\\mathrm{W\\,m^{-1}\\,K^{-1}}$) making $z_N$ large.","core_discovery":"On its own terms the paper's central claim is that high Nernst performance does not require topological bands. In ScSb, which the authors classify as topologically trivial from the absence of band inversion, they measure a Nernst peak of about $47\\,\\mu\\mathrm{V}/\\mathrm{K}$ at 12 K and 14 T, a maximum Nernst power factor of about $35 \\times 10^{-4}\\,\\mathrm{W\\,m^{-1}\\,K^{-2}}$, and a Nernst figure of merit of about $28 \\times 10^{-4}\\,\\mathrm{K^{-1}}$. They attribute the peak to the combination of strong phonon drag and nearly equal electron and hole densities, with $n_h/n_e \\approx 1.05 \\pm 5\\%$ from transport measurements, while density functional theory Fermi-surface volumes give about 1.31, a difference they trace to a Fermi-level shift of roughly $0.04\\,\\mathrm{eV}$. Because ScSb is a trivial compensated semimetal, they conclude that the Berry-curvature anomalous Nernst effect is not the primary contributor to the enhanced thermomagnetic performance seen in topological semimetals.","pith_inferences":["The peak-value comparison against topological semimetals mixes samples measured at different temperatures and fields; a fairer comparison would map $S_{xy}(T,B)$ on the same grid or normalize by carrier density.","A direct test of the phonon-drag attribution would be isotope substitution: replacing Sb with a heavier isotope should shift the phonon-drag peak in temperature while leaving the electronic structure essentially unchanged, and the Nernst peak should move with it.","If compensation is the controlling factor, doping ScSb away from $n_h = n_e$ should suppress the Nernst peak; this prediction is measurable and would separate compensation from phonon drag.","The same logic suggests a search strategy for other topologically trivial, highly compensated semimetals, which could yield inexpensive thermomagnetic materials without the band-structure engineering needed for topological semimetals."],"forward_implications":["If correct, the result removes topology as a prerequisite for a strong Nernst response: ordinary compensated semimetals with phonon drag become candidate thermomagnetic refrigerators.","Because ScSb is cubic, the same performance should appear in polycrystalline form, and suppressing grain-boundary electron scattering while increasing boundary phonon scattering could raise $z_N$ further.","Tuning the carrier balance toward perfect compensation, for instance by shifting the Fermi level to match the density functional theory prediction, is a concrete lever for pushing the Nernst power factor higher.","The comparison implies that part of the large Nernst signal in topological semimetals may be non-topological, so measurements on trivial members of the same families are needed to separate the contributions."],"supporting_citations":[{"why":"Provides prior quantum-oscillation evidence on ScSb's near compensation and Fermi-surface parameters that the transport analysis is checked against.","marker":"[11]"},{"why":"Prior transport study of ScSb that reported phonon-drag behavior and compensation; cited as the basis for the same combination in this paper.","marker":"[12]"},{"why":"Reports the large Nernst effect in the topological semimetal Cd3As2, the main benchmark for the comparison.","marker":"[1]"},{"why":"Supplies the ZrTe5 Nernst power-factor and figure-of-merit benchmark used in the comparison.","marker":"[3]"},{"why":"Provides the comparative topological-semimetal Nernst data, including TbPtBi, used to place ScSb's values.","marker":"[6]"},{"why":"Gives the recent topological-semimetal Nernst figure-of-merit benchmark that ScSb is compared against.","marker":"[13]"}],"fun_headline_variants":["Trivial ScSb matches topological Nernst values","Electron-hole balance lifts Nernst in trivial ScSb","Phonon drag drives ScSb's Nernst to topology-class levels","ScSb proves high Nernst doesn't require topological bands"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the 12 K Nernst peak in ScSb is produced by phonon drag acting on nearly perfectly compensated electrons and holes; if that attribution fails, the proposed mechanism loses its support, although the measured values themselves remain valid.","fun_headline_variants_meta":{"raw":{"variants":["Trivial ScSb matches topological Nernst values","Electron-hole balance lifts Nernst in trivial ScSb","Phonon drag drives ScSb's Nernst to topology-class levels","ScSb proves high Nernst doesn't require topological bands"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000374,"raw_usage":{"total_tokens":2063,"prompt_tokens":1078,"completion_tokens":985,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":694,"completion_tokens_details":{"reasoning_tokens":913}},"tokens_in":694,"tokens_out":985,"duration_ms":8662,"temperature":1.0,"reasoning_tokens":913,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-16T11:25:55.453565+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the Nernst thermopower in ScSb samples whose electron-hole ratio is deliberately shifted away from unity by slight Sb deficiency or doping: if the 12 K peak and the large power factor survive, compensation is not the controlling mechanism; a quantitative transport calculation that includes phonon drag and uses the measured carrier densities and mobilities should reproduce the ~$47\\,\\mu\\mathrm{V}/\\mathrm{K}$ peak, and if it cannot, the phonon-drag attribution is unsupported.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Prior transport study of ScSb that reported phonon-drag behavior and compensation; cited as the basis for the same combination in this paper."},{"cited_title":"6(a) and (b), respectively","cited_arxiv_id":null,"evidence_quote":"Reports the large Nernst effect in the topological semimetal Cd3As2, the main benchmark for the comparison."},{"cited_title":"Xiang, S","cited_arxiv_id":null,"evidence_quote":"Supplies the ZrTe5 Nernst power-factor and figure-of-merit benchmark used in the comparison."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the comparative topological-semimetal Nernst data, including TbPtBi, used to place ScSb's values."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Gives the recent topological-semimetal Nernst figure-of-merit benchmark that ScSb is compared against."}],"review_version":1}