{"id":"d48ff96d-89f9-428b-a0d9-0e9a04de4c46","arxiv_id":"1908.07728","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"In Dy3Ru4Al12, magnetic field switches the stacking of non-coplanar spin trimers and turns on a large geometrical Hall effect linked to net scalar spin chirality.","lead":"A magnetic material with a breathing kagome lattice shows field-switchable patterns of triangular spin arrangements, and the patterns with leftover spin chirality produce a large Hall effect. The result ties a measurable electronic transport signal to a topological real-space magnetic structure.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Normal Hall background subtraction is the load-bearing weak point; the authors' own Supplement VI admits low-T normal Hall changes cannot be excluded, so the sharp sigma_A features and the ratio ~3.8 may be partly normal-Hall artifacts.","rationale":"The reader's weakest-assumption identification is exactly the most load-bearing concern: the normal Hall background measured at 300 K is assumed valid at 2 K, yet the authors' own Supplemental analysis explicitly admits that the low-temperature normal Hall conductivity may change due to a high-mobility pocket, and that the strong bending of sigma_xy at 2.5 K may be partly normal Hall in origin. This concern directly threatens the central mechanism attribution, because a field- or temperature-dependent normal Hall term could produce step-like features or a sharp rise near the magnetic transitions without any chirality contribution. The concern does not force rejection, however: the observation that sigma_A is zero in the zero-net-chirality phase I, the contrast between sigma_A(T) and M(T), and the SdH evidence against major band reconstruction are genuine supporting checks. The paper is therefore best left at the reader's CONDITIONAL verdict: the mechanism claim is plausible and well-supported in its main qualitative correlation, but not uniquely established until the normal Hall background is independently constrained at low temperature. I recommend no change to the verdict, with the concrete re-analysis described above as the decisive test.","tokens_in":17915,"tokens_out":6331,"duration_ms":71090,"concrete_test":"Re-analyze the raw rho_yx(H, T) data using a low-temperature normal Hall background determined independently of the 300 K slope: fit sigma_xy(H) at T >= 10 K with the two-band Drude form sigma_N_xy = aB + bB/(1 + (mu*B)^2) of Supplement VII, constrain mu and the pocket size with the SdH parameters (F = 83 T, mu ~ 900 cm^2/(V s)), extrapolate to T = 2 K, and recompute sigma_A_xy in phases I-III. If the step at ~1.2 T and the ~5 K rise in sigma_A shrink or shift such that phase I no longer returns sigma_A = 0, or the phase III/II ratio moves away from ~3.8, then normal-Hall contamination is confirmed and the chirality attribution is not uniquely established.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that the large Hall response in phases II and III is a chirality-induced geometrical Hall effect depends on isolating the anomalous Hall conductivity sigma_A_xy from a presumed smooth normal Hall background. The isolation uses Supplemental Eq. (3), rho_A_yx = rho_yx - rho_N_yx(300 K), i.e. the normal Hall slope at 300 K is assumed unchanged at 2 K. This assumption is directly weakened by the authors' own Supplement VI: a high-mobility small carrier pocket (SdH F = 83 T, mu ~ 300-800 cm^2/(V s), possibly ~900 cm^2/(V s)) makes sigma_N_xy bend already at T >= 10 K, and the two-band Drude fit requires a field-dependent normal term. The supplement states: 'From our data, it cannot be excluded that mu increases in magnitude below the transition to long-range order (~5 K). The strong bending of sigma_xy(T = 2.5 K, H) may be at least partially due to sigma_N_xy.' If the normal Hall coefficient changes at the magnetic transition or with field, the sharp rise in sigma_A(T) at 9 T and the step at ~1.2 T could be partly normal-Hall artifacts. The 'sanity check' sigma_A = 0 in phase I only constrains the combined subtraction at one low-field regime; it does not establish field or temperature independence of the background. Because the same 300 K slope is also subtracted when computing the phase III/II ratio ~3.8, the quantitative support for the chirality origin rests on this insecure subtraction.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports neutron diffraction and magnetotransport measurements on the breathing kagome compound Dy3Ru4Al12. It identifies three field-induced magnetic phases: phase I with a vanishing global scalar spin chirality, and phases II and III with non-coplanar spin trimers carrying nonzero net chirality. Using single-crystal neutron refinements, the authors determine the magnetic structures and extract local chirality values χ0 ≈ 0.17 and χ'0 ≈ 0.23. Hall measurements show a large anomalous Hall conductivity that becomes nonzero in phases II and III and vanishes in phase I, with a step-like field dependence and a sharp rise in temperature at the phase-II/III boundary. The authors attribute this to a real-space Berry-phase (geometrical) Hall effect and support this with a semi-quantitative comparison: since σ_A_xy ∝ p χ_tot and p ∝ M, the ratio between phases III and II is predicted to be ~3.8, close to the observed ratio.","tokens_in":18264,"tokens_out":5333,"duration_ms":49572,"significance":"If the chirality attribution holds, this is a compelling demonstration of a geometrical Hall effect arising from tunable spin trimers, with the unusual feature that the local chirality can be switched by an external magnetic field and is determined independently by neutron diffraction. The main strengths are the direct neutron refinement of the chirality-bearing structures, the clean internal check that σ_A_xy = 0 in phase I, and the fact that the transport and neutron results are compared through a theoretical scaling relation rather than fitted to each other. The paper also discusses and partially rules out extrinsic and momentum-space mechanisms using the temperature dependence of σ_A_xy relative to M(T). The quantitative comparison is, however, sensitive to the normal Hall background subtraction and to the quality of the phase-III refinement, which are the points addressed below.","major_comments":[{"comment":"The isolation of the anomalous Hall conductivity rests on subtracting the normal Hall resistivity measured at 300 K from the low-temperature data, ρA_yx = ρ_yx − ρ_N_yx(300 K). The authors themselves state in Supplement VI that a small carrier pocket with μ ≈ 300–800 cm^2/(V s) causes σ_N_xy to bend already at T ≥ 10 K, and that 'it cannot be excluded that μ increases in magnitude below the transition to long-range order (~5 K). The strong bending of σ_xy(T = 2.5 K, H) may be at least partially due to σ_N_xy.' Because the same background is subtracted for both phases II and III, the step-like features in σ_A_xy(H) and the sharp rise in σ_A_xy(T) at 9 T could be partly normal-Hall artifacts rather than pure chirality signals. The phase-I null of σ_A_xy is a useful consistency check, but it only constrains the combined subtraction in one low-field regime; it does not establish that the normal Hall coefficient is field- and temperature-independent across phases II and III. The quantitative ratio ~3.8 therefore inherits this uncertainty. I request a quantitative estimate of the normal Hall contribution in phases II and III, e.g., by fitting the two-band model to the low-temperature data or by propagating the uncertainty in μ through the subtraction, and a discussion of how the conclusions would change under a field-dependent normal Hall term.","section":"Supplement VI, Eq. (3)"},{"comment":"The predicted ratio σ_A_xy(III)/σ_A_xy(II) ≈ 3.8 rests on the refined chirality values χ_0 ≈ 0.17 and χ'_0 ≈ 0.23 together with the assumption that the geometrical weights of the nearest-neighbor trimers and the second-neighbor triangles are 'dominant and comparable.' The phase-II refinement is good (R_f2 = 15.6%), but the phase-III refinement has R_f2 = 25.9% (Supplement III), and no error bars are given for χ_0 or χ'_0. Since the chirality in phase III is derived from the in-plane spin components that are reoriented from all-in-all-out to tangential, a 26% R-factor leaves substantial room for alternative structures with different χ'_0. In addition, the 'dominant and comparable' weighting is an ad-hoc assumption that is not derived from the band structure or the coupling strength. Please provide the refined moment directions with uncertainties, propagate them to χ_tot for both phases, and test the sensitivity of the predicted ratio to the assumed geometrical weights.","section":"Main text, Fig. 2 and semi-quantitative comparison"}],"minor_comments":[{"comment":"The word 'wavefuntion' in the abstract should be 'wavefunction'.","section":"Abstract"},{"comment":"'Our works provide' should be 'Our work provides'.","section":"Main text, concluding paragraph"},{"comment":"'Anistropic couplings' should be 'anisotropic couplings', and 'the magntic properties' should be 'the magnetic properties'.","section":"Supplement V"},{"comment":"The tick labels '73 50' on the vertical axis are unclear; please add explicit axis labels and units.","section":"Fig. 1c"},{"comment":"Given the subtraction uncertainty discussed in Supplement VI, the phrase 'unambiguous illustration' is too strong; consider softening it.","section":"Main text, concluding paragraph"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is well written and the neutron refinements in phases I and II are solid. The main concern is the normal Hall background subtraction, which the authors themselves flag in Supplement VI. If the authors can provide a quantitative estimate of the normal Hall contribution (e.g., via two-band fits or an uncertainty band) and propagate it through the σ_A_xy analysis and the ratio comparison, I would support publication. The phase-III refinement R_f2 = 25.9% also warrants more caution in the claimed ratio."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Short version: this is a serious experimental paper with a new result and one load-bearing assumption that is shakier than the main text lets on. The authors show that in Dy3Ru4Al12, a magnetic field switches the stacking of non-coplanar spin trimers so that the global scalar spin chirality goes from zero to nonzero, and the anomalous Hall conductivity does the same. The zero-chirality phase having sigma_A = 0 is a clean internal check, and the step-like Hall signal across the phase boundaries, with a temperature dependence that does not track magnetization, is the right kind of evidence for a chirality-driven term. The neutron refinements in phases I and II (Rf2 ~16%) are decent, and the phase III structure gets an independent cross-check from the extinction rule even though the Rf2 is 25.9%.\n\nThe soft spot is the normal Hall subtraction. The main text subtracts the 300 K normal Hall slope to get sigma_A, and the quantitative claim that the phase III/II ratio is ~3.8 relies on that. But Supplement VI says plainly that a small, high-mobility pocket makes sigma_N_xy bend already at T >= 10 K, that the two-band fit needs a field-dependent term, and that 'it cannot be excluded that mu increases below the transition.' That means the sharp rise in sigma_A(T) at 9 T and the step at ~1.2 T could be partly normal Hall artifacts. The phase I null only constrains the combined subtraction in one low-field regime; it does not establish field or temperature independence of the background. So the central mechanism claim is plausible but not proven. This is not a fatal flaw, but it is exactly where a referee should push.\n\nThe other soft spots are minor. The 3.8 comparison depends on p proportional to M and comparable geometrical weights—simplifications that make it suggestive rather than decisive. And the authors themselves note SOC cannot be fully excluded; that is honest, not a strike.\n\nI believe the paper deserves peer review. The field-induced switching of spin-trimer chirality and the corresponding Hall response is new, and the data are good enough that the community will want to know whether the mechanism holds up. My recommendation: send it to a strong referee, with a request that the normal Hall subtraction be examined carefully.","headline":"Solid new experiment on field-tunable spin-trimer chirality and Hall effect, but the normal Hall subtraction—the load-bearing assumption—is weaker than the main text admits.","tokens_in":18848,"tokens_out":1973,"would_cite":true,"duration_ms":20731,"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 large Hall conductivity in Dy3Ru4Al12 is a geometrical Hall effect from non-coplanar spin trimers.","keywords":["scalar spin chirality","geometrical Hall effect","Berry phase","spin trimers","breathing kagome lattice","Dy3Ru4Al12","neutron diffraction","anomalous Hall conductivity"],"falsifier":"Measure the Hall resistivity at 2 K in the high-field regime above about 9 T, where the trimer chirality is suppressed and moments align with the $c$ axis; if the signal obtained after subtracting the 300 K normal slope does not drop to zero, or if a two-band Drude fit to the high-field normal Hall reproduces the step-like features assigned to chirality, the mechanism assignment would be falsified.","tokens_in":17714,"feed_emoji":"🧲","tokens_out":7621,"duration_ms":130192,"temperature":0.7,"pith_summary":"The paper claims that the large anomalous Hall conductivity observed in the field-induced phases II and III of the metallic magnet Dy3Ru4Al12 is a \"geometrical Hall effect\": conduction electrons pick up a real-space Berry phase as they hop around non-coplanar spin trimers, so the transverse voltage tracks the net scalar spin chirality of the crystal rather than its magnetization alone. Using single-crystal neutron diffraction, the authors determine the magnetic structures of three phases and show that a magnetic field switches between an antiferroic stacking of trimers with zero net chirality (phase I) and ferroic or twisted arrangements with nonzero net chirality (phases II and III). Magneto-transport measurements show the Hall conductivity is zero in phase I, rises sharply at the onset of the chiral phases, and changes in step-like jumps at the phase boundaries. A semi-quantitative estimate $\\sigma^A_{xy}\\propto p\\chi_{\\mathrm{tot}}$ with $p\\propto M$ predicts a phase-III-to-II Hall-conductivity ratio near 3.8, matching the measured ratio. If correct, the work is a clear experimental demonstration that tunable spin trimers on a breathing kagome lattice can produce large emergent electromagnetic responses of real-space Berry-phase origin.","feed_headline":"Spin trimers drive a large Hall effect","feed_subtitle":"Neutron diffraction ties the sharp Hall jump to nonzero net scalar spin chirality.","key_machinery":"The load-bearing object is the scalar spin chirality $\\chi_{ijk}=\\mathbf{S}_i\\cdot(\\mathbf{S}_j\\times\\mathbf{S}_k)$, the signed solid angle subtended by three neighboring spins; when electrons hop around such a triangle they acquire a Berry phase equivalent to that from a fictitious magnetic flux. The paper combines this with the spin-trimer picture: strongly coupled Dy$^{3+}$ triangles act as rigid units whose in-plane all-in/all-out or twisted configurations carry a well-defined local chirality, so the crystal's net chirality is set entirely by how the trimers stack. The quantitative bridge between magnetism and transport is the proportionality $\\sigma^A_{xy}\\propto p\\,\\chi_{\\mathrm{tot}}$ with $p\\propto M$, justified in the weak-coupling regime; it converts the neutron-diffraction chirality values $\\chi_0\\approx 0.17$ and $\\chi_0'\\approx 0.23$ into a predicted Hall-conductivity ratio of about 3.8 between phases III and II.","core_discovery":"The central discovery, stated on the paper's own terms, is that the local scalar spin chirality of the Dy$^{3+}$ spin trimers can be ordered and switched by magnetic field, and that the resulting net chirality directly produces a large geometrical Hall effect. In zero-field phase I the trimers are all-in/all-out with local chirality $\\chi_0\\approx 0.17$, but the signs alternate between neighboring unit cells, so the net chirality of the crystal is zero and $\\sigma^A_{xy}=0$. Field-induced phase II with $q_2=(1/3\\,1/3\\,0)$ arranges the trimer chirality in a $+/+/-$ sequence along $a$ and $b$, giving an average chirality of $\\chi_0/3$ on nearest-neighbor trimers and an equal contribution on second-neighbor triangles; here the anomalous Hall conductivity becomes nonzero. In phase III the in-plane moments twist so that nearest-neighbor trimers carry negative chirality $-\\chi_0'/3$ while the second-neighbor triangles carry a positive net chirality $\\chi_0'$, and the Hall conductivity grows further. The authors rule out skew scattering by the $\\tau$-independence of the step-like $\\sigma^A_{xy}(H)$ and rule out Karplus-Luttinger and side-jump mechanisms by the sharp rise of $\\sigma^A_{xy}(T)$ at constant magnetization, attributing the signal to the real-space Berry phase of the non-coplanar spin texture.","pith_inferences":["If the geometrical-Hall assignment is correct, the same subtraction scheme applied in a field-aligned, chirality-free state should give $\\sigma^A_{xy}=0$; a direct measurement of the 2 K normal Hall coefficient, rather than the 300 K value, would settle whether part of the step is an ordinary Hall artifact.","The equivalence between real-space and momentum-space Berry phases invoked for short-period lattices suggests that other members of the R$_3$Ru$_4$Al$_{12}$ family with different rare-earth anisotropy could show chirality-controlled Hall responses with sign and magnitude predictable from the trimer stacking.","A natural testable extension is to rotate the magnetic field away from the $c$ axis: the predicted Hall response should track the chirality components selected by the field, not merely the projected magnetization."],"forward_implications":["In any phase of Dy3Ru4Al12 where the spin-trimer stacking cancels all chirality, the anomalous Hall conductivity vanishes, so the Hall signal can be used as a bulk probe of net scalar spin chirality.","The magnitude and sign of the Hall response are set by the stacking pattern of trimers, meaning magnetic field can act as a switch between zero, moderate, and large geometrical Hall states.","Because $\\sigma^A_{xy}$ is independent of the scattering time and does not follow magnetization, the observation separates real-space Berry-phase transport from the spin-orbit-coupling mechanisms that dominate conventional ferromagnets.","Compound families with breathing kagome lattices and tunable Dzyaloshinskii-Moriya or single-ion anisotropy should show analogous field-tunable geometrical Hall responses wherever rigid non-coplanar trimers form."],"supporting_citations":[{"why":"Review of anomalous Hall mechanisms used to identify which conventional contributions (skew scattering, Karplus-Luttinger, side-jump) must be excluded.","marker":"[6]"},{"why":"Theory that non-zero scalar spin chirality on triangular plaquettes induces a geometrical Hall effect of real-space Berry-phase origin.","marker":"[7–11]"},{"why":"The kagome-lattice chiral-spin-state model that gives the minimal one-triangle picture of a Berry-phase Hall response.","marker":"[8]"},{"why":"Weak-coupling treatment in which the chirality-induced Hall conductivity is proportional to spin polarization times total chirality, providing the 3.8 ratio estimate.","marker":"[10, 11]"},{"why":"Supplemental details of sample growth, neutron refinements, and the normal-Hall subtraction procedure used to isolate the anomalous Hall conductivity.","marker":"[12]"},{"why":"Prior determination of the crystal structure and magnetic phases of Dy3Ru4Al12 that this study's field-induced phases and trimer structures build on.","marker":"[25]"}],"fun_headline_variants":["Spin trimer chirality orders and switches Hall effect","Field-tunable spin trimers yield large Hall signal","Real-space Berry phase from spin trimers drives Hall jump","Scalar spin chirality order controls geometrical Hall effect","Spin trimers: switchable chirality, big Hall response"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the ordinary Hall resistivity measured at 300 K remains a valid background at 2 K, so after subtracting that linear slope the residual anomalous Hall conductivity is entirely due to spin chirality and not to a field- or temperature-dependent change in the normal Hall coefficient.","fun_headline_variants_meta":{"raw":{"variants":["Spin trimer chirality orders and switches Hall effect","Field-tunable spin trimers yield large Hall signal","Real-space Berry phase from spin trimers drives Hall jump","Scalar spin chirality order controls geometrical Hall effect","Spin trimers: switchable chirality, big Hall response"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000172,"raw_usage":{"total_tokens":1355,"prompt_tokens":1107,"completion_tokens":248,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":723,"completion_tokens_details":{"reasoning_tokens":168}},"tokens_in":723,"tokens_out":248,"duration_ms":104455,"temperature":1.0,"reasoning_tokens":168,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T11:57:46.798882+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the Hall resistivity at 2 K in the high-field regime above about 9 T, where the trimer chirality is suppressed and moments align with the $c$ axis; if the signal obtained after subtracting the 300 K normal slope does not drop to zero, or if a two-band Drude fit to the high-field normal Hall reproduces the step-like features assigned to chirality, the mechanism assignment would be falsified.","supporting_citations":[{"cited_title":"Ohgushi, S","cited_arxiv_id":null,"evidence_quote":"The kagome-lattice chiral-spin-state model that gives the minimal one-triangle picture of a Berry-phase Hall response."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplemental details of sample growth, neutron refinements, and the normal-Hall subtraction procedure used to isolate the anomalous Hall conductivity."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Prior determination of the crystal structure and magnetic phases of Dy3Ru4Al12 that this study's field-induced phases and trimer structures build on."}],"review_version":1}