# Hall-coefficient sign reversal: carriers, mobility and evidence

Separate a Hall sign change from a Hall-number inference, account for multiband mobility and anomalous terms, and retain each experiment's normal-state boundary.

## Scope

A Hall-coefficient sign reversal is a change in the sign of the transverse response under a declared wiring and field convention. It is distinct from a change in Hall magnitude, a peak, or an inferred Hall number. Electron and hole contributions can exchange transport weight without either Fermi-surface pocket disappearing. Neither a sign change nor a Hall anomaly by itself proves superconductivity, a Lifshitz transition or a particular pairing mechanism. [R1](#ref-source-7acbaed4e62141d9) [R2](#ref-source-8c3b378d8802f683) [R3](#ref-source-e24f6678715b4917) [R5](#ref-source-fae77f2c38d4cf72)

Here $E_y=R_HJ_xB_z$ defines the sign. The elementary single-band Drude values are $R_H=-1/(n_e e)$ for electrons and $R_H=1/(n_h e)$ for holes, with $e>0$. These density interpretations require restrictive assumptions. Even a single crystalline band can have a complicated Hall response because Fermi-surface curvature and a momentum-dependent mean free path affect the weak-field conductivity. A temperature-dependent Hall coefficient is therefore not sufficient evidence for multiple bands. [R7](#ref-source-fd33407c49db2caf)

## Mathematical assumptions

For independent isotropic electron and hole Drude channels with positive mobilities and $\mu_i B\ll1$, $R_H=(n_h\mu_h^2-n_e\mu_e^2)/[e(n_h\mu_h+n_e\mu_e)^2]$. The sign changes when the mobility-squared weights cross. Fixed carrier densities can therefore produce a reversal as the mobility ratio varies. At zero field $\sigma_0=e(n_h\mu_h+n_e\mu_e)$; even simultaneous values of $\sigma_0$ and weak-field $R_H$ do not uniquely determine four density/mobility parameters. Independent tensor-inversion checks illustrate this degeneracy without fitting a material. [R4](#ref-source-362cf0fd861683c3) [R7](#ref-source-fd33407c49db2caf)

Beyond weak field, add conductivity tensors and invert the sum. In the same classical model, when both $\mu_iB\gg1$ and $n_h\ne n_e$, the asymptotic slope is $\rho_{yx}/B\to1/[e(n_h-n_e)]$. Exact compensation is a different limit: for $n_h=n_e=n$, $\rho_{yx}/B=(\mu_h-\mu_e)/[en(\mu_h+\mu_e)]$ at all fields in this model. A large laboratory field alone establishes neither of these asymptotic conditions. Quantum effects, coupled scattering and reconstructed bands may require a different model. [R4](#ref-source-362cf0fd861683c3) [R7](#ref-source-fd33407c49db2caf)

Ordinary and anomalous contributions must also be distinguished. A schematic $\rho_{yx}=R_0B+\rho_{yx}^{A}$ is not a universal fit, and an anomalous term need not be proportional to magnetization with a constant coefficient. Intrinsic Berry curvature, skew scattering and side jump are distinct mechanisms. Field antisymmetrization, $[\rho_{yx}(B)-\rho_{yx}(-B)]/2$, removes even longitudinal contact leakage but retains an odd anomalous Hall contribution. It does not isolate ordinary Hall transport by itself. [R6](#ref-source-7faba5d556864a32)

## Experimental criteria

Tsukada and Ono studied epitaxial La2−xSrxCuO4 films on SrTiO3 with residual tensile strain. Their room-temperature Hall coefficient changes from positive to negative between x=0.28 and x=0.32. The heavily overdoped samples used field sweeps to ±6 T. This is a sample-series result at 300 K, not a universal cuprate doping boundary. The x=0.32 film lacks zero resistance but has a reported resistive onset, which the authors discuss in relation to possible oxygen inhomogeneity. Describing it simply as having no superconducting evidence would erase that distinction. [R1](#ref-source-7acbaed4e62141d9)

Brouet's Ba(Fe0.65Ru0.35)2As2 study reports a temperature-dependent Hall sign together with electron and hole pockets. The checked primary abstract supports that limited statement; complete transport methods and a precise reversal temperature remain unreviewed here. Mun's Co- and Cu-substituted BaFe2As2 crystals provide a separate comparison: thermopower and Hall changes occur at comparable added-electron counts, but the Cu comparison does not show the corresponding resistive superconductivity. These Hall anomalies are not a superconductivity criterion or a universal sign-change threshold. [R2](#ref-source-8c3b378d8802f683) [R3](#ref-source-e24f6678715b4917)

Mun's experiment measured composition by wavelength-dispersive spectroscopy and applied the Hall field along the crystal c axis, reversing field polarity to reduce contact offsets. Its 25 K comparison is a measurement temperature, not a transition temperature. Sample exfoliation can alter geometric factors, so normalized trends and absolute Hall magnitudes carry different uncertainties. Co/Cu substitution fraction and inferred added-electron count are also different horizontal axes. [R3](#ref-source-e24f6678715b4917)

Iida's strained Ba(Fe1−xCox)2As2 films used MgO and CaF2 substrates and Hall measurements at 9 T. Their effective Hall number $n_H=V/(4e|R_H|)$, with unit-cell volume $V$, is positive by construction and expressed per Fe. It discards the Hall sign and is not a direct count of all mobile carriers in a multiband metal. The reported phase-diagram alignment concerns the studied strained films and selected bulk comparisons. The superconducting temperature uses a resistive onset criterion, rather than silently substituting zero resistance or magnetic shielding. [R4](#ref-source-362cf0fd861683c3)

Badoux's YBa2Cu3Oy experiment distinguishes a charge-order reconstruction endpoint near p=0.16 from a pseudogap endpoint near p=0.19. The Hall-number interpretation changes from approximately 1+p toward p; this is not evidence for a mandatory Hall-sign reversal at the latter point. Pulsed fields reached 88 T, with a 50 K, 80 T cross-sample comparison. The author manuscript establishes normal-state access down to at least 40 K and explicitly leaves the lower-temperature p=0.16 behavior unresolved. Its vortex-melting field is not automatically the upper critical field. [R5](#ref-source-fae77f2c38d4cf72)

## Limits and disputes

Normal-state extraction needs more than a high-field label. Retain temperature, current, field direction, hysteresis branch and the independently justified superconducting boundary; vortex motion and magnetic contributions can contaminate a transverse signal. Yang's field-induced superconductivity study is a boundary example, not a source of an ordinary-Hall reversal field. Its superconducting phase-diagram scales must not be relabeled as Hall or anomalous-Hall thresholds. [R5](#ref-source-fae77f2c38d4cf72) [R6](#ref-source-7faba5d556864a32) [R8](#ref-source-3504ee9027165d0a)

Complete scientific acceptance remains open. Most experimental checks here cover selected author-manuscript methods, results and figures, not complete final articles or raw-data reproduction. Brouet remains abstract-scoped; Ong's full geometric derivation and the anomalous-Hall review remain incompletely read. Apparent numeric typographical inconsistencies in the Mun and Iida author versions require final-version comparison; those uncertain composition values are not adopted. The independent Drude checks establish model algebra, not a unique interpretation of any experimental Hall curve. [R1](#ref-source-7acbaed4e62141d9) [R2](#ref-source-8c3b378d8802f683) [R3](#ref-source-e24f6678715b4917) [R4](#ref-source-362cf0fd861683c3) [R5](#ref-source-fae77f2c38d4cf72) [R6](#ref-source-7faba5d556864a32) [R7](#ref-source-fd33407c49db2caf)

## Discovery implications

Treat a sign change as a prompt to test competing transport explanations. Combine field-dependent longitudinal and transverse resistivity, magnetoresistance, magnetic characterization and independent Fermi-surface information. Compare constrained models and retain geometry, strain, oxygen content and uncertainty. A mobility crossover, reconstructed Fermi surface and anomalous contribution can produce different predictions beyond a single Hall slope; a defensible conclusion specifies which alternatives the measurements actually exclude. [R1](#ref-source-7acbaed4e62141d9) [R2](#ref-source-8c3b378d8802f683) [R4](#ref-source-362cf0fd861683c3) [R5](#ref-source-fae77f2c38d4cf72) [R7](#ref-source-fd33407c49db2caf)

## Related topics

[Parallel conduction channels](/scwiki/parallel-conduction-channels), [Nonlinear Hall effect](/scwiki/nonlinear-hall-effect), and [Field-induced superconductivity](/scwiki/field-induced-superconductivity).

## Material cases

Values describe individual reports, not a ranking. Unknown means the checked source did not supply the field at this review scope.

| Material and sample | Reported temperature | Criterion | Probe | Pressure | State | Evidence |
|---|---|---|---|---|---|---|
| La2-xSrxCuO4 (aliases: LSCO, La2-xSrxCuO4); Tsukada epitaxial LSCO films on SrTiO3; room-temperature doping series | 300 K; Hall measurement temperature, not a superconducting transition temperature. | measurement; normal-state-hall-measurement | Transverse transport with applied field | ambient; unknown GPa | unknown | experiment; [source](#ref-source-7acbaed4e62141d9) |
| Ba(Fe1-xCox)2As2 (aliases: Co-doped Ba122, Ba(Fe1-xCox)2As2); Mun WDS-characterized Co-substituted crystals; Figure5 | 25 K; Hall measurement temperature, not a superconducting transition temperature. | measurement; normal-state-hall-measurement | Transverse transport with applied field | ambient; unknown GPa | unknown | experiment; [source](#ref-source-e24f6678715b4917) |

## Sources

### Ref source-7acbaed4e62141d9

[R1] Negative Hall coefficients of heavily overdoped La2-xSrxCuO4 (2006). [DOI 10.1103/PhysRevB.74.134508](https://doi.org/10.1103/PhysRevB.74.134508). Publication: journal-article. Check: selected-author-methods-and-figure-check. Checked: 2026-10-19. Author v2,25August2006: selected pp1–6 andp10caption read;p11Figure2 visually checked. Tensile-strained epitaxial films on SrTiO3(100); Hall sweeps ±1T forx.08–.22 and ±6T forx.24–.40. Atx.32 no zero resistance but onset is reported, possibly from oxygen inhomogeneity. Final comparison/raw data remain open.
### Ref source-8c3b378d8802f683

[R2] Significant reduction of electronic correlations upon isovalent Ru substitution of BaFe2As2 (2010). [DOI 10.1103/PhysRevLett.105.087001](https://doi.org/10.1103/PhysRevLett.105.087001). Publication: journal-article. Check: publisher-abstract-check. Checked: 2026-10-19. Publisher abstract checked: Ba(Fe0.65Ru0.35)2As2 electron/hole pockets and temperature-dependent Hall sign. Full sample/transport methods not read; no precise sign-change temperature extracted.
### Ref source-e24f6678715b4917

[R3] Thermoelectric power and Hall coefficient measurements on Ba(Fe1-xTMx)2As2 (TM=Co and Cu) (2009). [DOI 10.1103/PhysRevB.80.054517](https://doi.org/10.1103/PhysRevB.80.054517). Publication: journal-article. Check: selected-author-methods-and-figure-check. Checked: 2026-10-19. Author v2,7August2009: selected pp1–6 read;p15Figure5 visually checked. WDS compositions, FeAs-flux crystals; AC four-wire Hall, field alongc, polarity reversed;25KFigure5 and90kOe temperature series. Exfoliation geometry uncertainty noted. p4 printed x>=0.38 conflicts with nearby0.038 scale: final-version comparison pending, numeric threshold not adopted.
### Ref source-362cf0fd861683c3

[R4] Hall-plot of the phase diagram for Ba(Fe1-xCox)2As2 (2016). [DOI 10.1038/srep28390](https://doi.org/10.1038/srep28390). Publication: journal-article. Check: selected-author-methods-and-figure-check. Checked: 2026-10-19. Author v2,10June2016; published22June2016. Selected p7Hall analysis, pp9–10methods,p18supplement Tc definition read; pp4Figure2 and9methods visually checked. Hall measured9T;14T belongs to separate MR/available field range. nH=V/(4e|RH|) perFe is positive by definition. p9prints0.74±0.017 for nominal0.08, an unresolved apparent typo; no measured concentration imported.
### Ref source-fae77f2c38d4cf72

[R5] Change of carrier density at the pseudogap critical point of a cuprate superconductor (2016). [DOI 10.1038/nature16983](https://doi.org/10.1038/nature16983). Publication: journal-article. Check: selected-author-methods-and-figure-check. Checked: 2026-10-19. Author v1,25November2015: selected pp1–5,pp28–29methods/errors read;p11Figure2 visually checked. Pulses to88T; normal-state coverage at least40K, lower-temperature p=.16 limit explicit. Figure2 uses vortex melting Hvs, not Hc2. Absolute geometry error up to15percent distinct from relative temperature uncertainty. Published online22February2016. Final/supplement/raw analysis incomplete.
### Ref source-7faba5d556864a32

[R6] Anomalous Hall effect (2010). [DOI 10.1103/RevModPhys.82.1539](https://doi.org/10.1103/RevModPhys.82.1539). Publication: journal-article. Check: review-abstract-background-check. Checked: 2026-10-19. Author review abstract checked; intrinsic Berry curvature and extrinsic scattering mechanisms. Background only, not a complete primary experimental audit.
### Ref source-fd33407c49db2caf

[R7] Geometric interpretation of the weak-field Hall conductivity in two-dimensional metals with arbitrary Fermi surface (1991). [DOI 10.1103/PhysRevB.43.193](https://doi.org/10.1103/PhysRevB.43.193). Publication: journal-article. Check: selected-final-first-page-check. Checked: 2026-10-19. Printedp193 scanned final page visually checked: abstract,introduction and startSectionII. Weak-field Boltzmann regime, mean-free-path curve l=v tau and Fermi-surface curvature; magnetic skew scattering and magnetic breakdown excluded. Complete geometric derivation not read.
### Ref source-3504ee9027165d0a

[R8] Field re-entrant superconductivity in Eu-doped infinite-layer nickelates (2026). [DOI 10.1038/s41586-026-10547-y](https://doi.org/10.1038/s41586-026-10547-y). Publication: journal-article. Check: selected-author-text-and-figures. Checked: 2026-10-18. Published23April2026; read authorv3 dated25April2026, selectedpp2–8, captionsp12, methodsp13–14; Fig2p19/Fig3p20 visually checked. Full final equivalence, calibration and all raw data remain open.

## Claim evidence and conditions

### scwiki-h9-claim-scope-1

A Hall-coefficient sign reversal is a change in the sign of the transverse response under a declared wiring and field convention. It is distinct from a change in Hall magnitude, a peak, or an inferred Hall number. Electron and hole contributions can exchange transport weight without either Fermi-surface pocket disappearing. Neither a sign change nor a Hall anomaly by itself proves superconductivity, a Lifshitz transition or a particular pairing mechanism.

Evidence: hypothesis. Sources: source-7acbaed4e62141d9, source-8c3b378d8802f683, source-e24f6678715b4917, source-fae77f2c38d4cf72.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-scope-2

Here $E_y=R_HJ_xB_z$ defines the sign. The elementary single-band Drude values are $R_H=-1/(n_e e)$ for electrons and $R_H=1/(n_h e)$ for holes, with $e>0$. These density interpretations require restrictive assumptions. Even a single crystalline band can have a complicated Hall response because Fermi-surface curvature and a momentum-dependent mean free path affect the weak-field conductivity. A temperature-dependent Hall coefficient is therefore not sufficient evidence for multiple bands.

Evidence: hypothesis. Sources: source-fd33407c49db2caf.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-mathematical-assumptions-1

For independent isotropic electron and hole Drude channels with positive mobilities and $\mu_i B\ll1$, $R_H=(n_h\mu_h^2-n_e\mu_e^2)/[e(n_h\mu_h+n_e\mu_e)^2]$. The sign changes when the mobility-squared weights cross. Fixed carrier densities can therefore produce a reversal as the mobility ratio varies. At zero field $\sigma_0=e(n_h\mu_h+n_e\mu_e)$; even simultaneous values of $\sigma_0$ and weak-field $R_H$ do not uniquely determine four density/mobility parameters. Independent tensor-inversion checks illustrate this degeneracy without fitting a material.

Evidence: theory. Sources: source-362cf0fd861683c3, source-fd33407c49db2caf.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-mathematical-assumptions-2

Beyond weak field, add conductivity tensors and invert the sum. In the same classical model, when both $\mu_iB\gg1$ and $n_h\ne n_e$, the asymptotic slope is $\rho_{yx}/B\to1/[e(n_h-n_e)]$. Exact compensation is a different limit: for $n_h=n_e=n$, $\rho_{yx}/B=(\mu_h-\mu_e)/[en(\mu_h+\mu_e)]$ at all fields in this model. A large laboratory field alone establishes neither of these asymptotic conditions. Quantum effects, coupled scattering and reconstructed bands may require a different model.

Evidence: theory. Sources: source-362cf0fd861683c3, source-fd33407c49db2caf.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-mathematical-assumptions-3

Ordinary and anomalous contributions must also be distinguished. A schematic $\rho_{yx}=R_0B+\rho_{yx}^{A}$ is not a universal fit, and an anomalous term need not be proportional to magnetization with a constant coefficient. Intrinsic Berry curvature, skew scattering and side jump are distinct mechanisms. Field antisymmetrization, $[\rho_{yx}(B)-\rho_{yx}(-B)]/2$, removes even longitudinal contact leakage but retains an odd anomalous Hall contribution. It does not isolate ordinary Hall transport by itself.

Evidence: theory. Sources: source-7faba5d556864a32.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-experimental-criteria-1

Tsukada and Ono studied epitaxial La2−xSrxCuO4 films on SrTiO3 with residual tensile strain. Their room-temperature Hall coefficient changes from positive to negative between x=0.28 and x=0.32. The heavily overdoped samples used field sweeps to ±6 T. This is a sample-series result at 300 K, not a universal cuprate doping boundary. The x=0.32 film lacks zero resistance but has a reported resistive onset, which the authors discuss in relation to possible oxygen inhomogeneity. Describing it simply as having no superconducting evidence would erase that distinction.

Evidence: experiment. Sources: source-7acbaed4e62141d9.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-experimental-criteria-2

Brouet's Ba(Fe0.65Ru0.35)2As2 study reports a temperature-dependent Hall sign together with electron and hole pockets. The checked primary abstract supports that limited statement; complete transport methods and a precise reversal temperature remain unreviewed here. Mun's Co- and Cu-substituted BaFe2As2 crystals provide a separate comparison: thermopower and Hall changes occur at comparable added-electron counts, but the Cu comparison does not show the corresponding resistive superconductivity. These Hall anomalies are not a superconductivity criterion or a universal sign-change threshold.

Evidence: experiment. Sources: source-8c3b378d8802f683, source-e24f6678715b4917.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-experimental-criteria-3

Mun's experiment measured composition by wavelength-dispersive spectroscopy and applied the Hall field along the crystal c axis, reversing field polarity to reduce contact offsets. Its 25 K comparison is a measurement temperature, not a transition temperature. Sample exfoliation can alter geometric factors, so normalized trends and absolute Hall magnitudes carry different uncertainties. Co/Cu substitution fraction and inferred added-electron count are also different horizontal axes.

Evidence: experiment. Sources: source-e24f6678715b4917.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-experimental-criteria-4

Iida's strained Ba(Fe1−xCox)2As2 films used MgO and CaF2 substrates and Hall measurements at 9 T. Their effective Hall number $n_H=V/(4e|R_H|)$, with unit-cell volume $V$, is positive by construction and expressed per Fe. It discards the Hall sign and is not a direct count of all mobile carriers in a multiband metal. The reported phase-diagram alignment concerns the studied strained films and selected bulk comparisons. The superconducting temperature uses a resistive onset criterion, rather than silently substituting zero resistance or magnetic shielding.

Evidence: experiment. Sources: source-362cf0fd861683c3.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-experimental-criteria-5

Badoux's YBa2Cu3Oy experiment distinguishes a charge-order reconstruction endpoint near p=0.16 from a pseudogap endpoint near p=0.19. The Hall-number interpretation changes from approximately 1+p toward p; this is not evidence for a mandatory Hall-sign reversal at the latter point. Pulsed fields reached 88 T, with a 50 K, 80 T cross-sample comparison. The author manuscript establishes normal-state access down to at least 40 K and explicitly leaves the lower-temperature p=0.16 behavior unresolved. Its vortex-melting field is not automatically the upper critical field.

Evidence: experiment. Sources: source-fae77f2c38d4cf72.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-limits-and-disputes-1

Normal-state extraction needs more than a high-field label. Retain temperature, current, field direction, hysteresis branch and the independently justified superconducting boundary; vortex motion and magnetic contributions can contaminate a transverse signal. Yang's field-induced superconductivity study is a boundary example, not a source of an ordinary-Hall reversal field. Its superconducting phase-diagram scales must not be relabeled as Hall or anomalous-Hall thresholds.

Evidence: hypothesis. Sources: source-fae77f2c38d4cf72, source-7faba5d556864a32, source-3504ee9027165d0a.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-limits-and-disputes-2

Complete scientific acceptance remains open. Most experimental checks here cover selected author-manuscript methods, results and figures, not complete final articles or raw-data reproduction. Brouet remains abstract-scoped; Ong's full geometric derivation and the anomalous-Hall review remain incompletely read. Apparent numeric typographical inconsistencies in the Mun and Iida author versions require final-version comparison; those uncertain composition values are not adopted. The independent Drude checks establish model algebra, not a unique interpretation of any experimental Hall curve.

Evidence: hypothesis. Sources: source-7acbaed4e62141d9, source-8c3b378d8802f683, source-e24f6678715b4917, source-362cf0fd861683c3, source-fae77f2c38d4cf72, source-7faba5d556864a32, source-fd33407c49db2caf.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

### scwiki-h9-claim-discovery-implications-1

Treat a sign change as a prompt to test competing transport explanations. Combine field-dependent longitudinal and transverse resistivity, magnetoresistance, magnetic characterization and independent Fermi-surface information. Compare constrained models and retain geometry, strain, oxygen content and uncertainty. A mobility crossover, reconstructed Fermi surface and anomalous contribution can produce different predictions beyond a single Hall slope; a defensible conclusion specifies which alternatives the measurements actually exclude.

Evidence: hypothesis. Sources: source-7acbaed4e62141d9, source-8c3b378d8802f683, source-362cf0fd861683c3, source-fae77f2c38d4cf72, source-fd33407c49db2caf.

Conditions: Retain sign convention, field and temperature, normal-state criterion, composition/strain, tensor model, geometry and source version. Hall number and sign are distinct.

Verification scope: Selected primary text/figures and independent Drude tensor checks; full scientific acceptance remains open.

## Revision and review

Article ID: scwiki-h9. Revision: 85ed19f928fa45dc6c34. Updated: 2026-10-18T17:26:39.189322+00:00.

Review scope: Selected Tsukada,Mun,Iida,Badoux author methods/results and figures; Ong final first page; Brouet primary abstract; inherited anomalous-Hall and Yang scopes; independent two-band tensor checks.

- Complete scientific acceptance remains open.
- Complete final-version comparison, supplementary controls, calibration and raw-data reproduction remain open.
- Brouet is abstract-scoped; Ong complete derivation and anomalous-Hall review not fully checked.
- Mun/Iida apparent author-version composition typos are recorded but not silently repaired or used.

Source: [H_anomalous_normal_state/H9_Hall_sign_reversal.md](https://github.com/JackZH26/jzis-superconductivity/blob/0a7c9d6696804ec26aa12f8eed68b55c9b3c0fcf/H_anomalous_normal_state/H9_Hall_sign_reversal.md), commit 0a7c9d6696804ec26aa12f8eed68b55c9b3c0fcf, SHA-256 34e045c73f1a28ec7177001c5fcf0edbced1a63d2ce2f2c8c5e6722f4ed19613.