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Superconducting dome and field-enhanced superconductivity of PLD synthesized Nd1-xEuxNiO2 thin films

T0 review · 2 major / 4 minor · reviewed 2026-07-14 · grok-4.5

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Pith's one-line read PLD-grown Eu-doped infinite-layer nickelate films show a wide superconducting dome peaking near 31 K and field-boosted superconductivity that the Jaccarino–Peter effect alone cannot explain.

desk verdict Solid PLD realization of a wide Eu-doped nickelate dome with ~31 K Tc and clear field-enhanced/re-entrant maps; the causal claim that CaH2 reduction makes PLD 'ideal' is correlative, not proven. read the letter →

arxiv 2607.10332 v1 pith:BREXOOZL submitted 2026-07-11 cond-mat.supr-con

Wenlong Yang , Qiang Zhao , Xingke Fu , Gaofei Ren , Zhongjing Wu , Zhen Chen , Jianping Sun , Boseng Wang
show 3 more authors
Jiacai Nie Pengtao Yang Jinguang Cheng
This is my paper
classification cond-mat.supr-con
keywords infinite-layernickelatesNd1-xEuxNiO2pulsedlaserdepositionsuperconductingdomefield-enhancedsuperconductivityre-entrantJaccarino-PetereffectEu2+magnetism
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper shows that pulsed-laser deposition followed by CaH2 topotactic reduction can produce high-quality Nd1-xEuxNiO2 infinite-layer thin films across a broad doping window. Resistivity data map a superconducting dome spanning 0.2 ≤ x ≤ 0.5, with the optimally doped x = 0.3 film reaching an onset Tc of about 31 K—higher than films made by other vacuum epitaxial methods and comparable to chemical-solution routes. Magnetotransport further reveals field-enhanced superconductivity on both underdoped and overdoped sides of the dome and re-entrant superconductivity at x = 0.5; in one underdoped film an 8 T in-plane field actually raises Tc above its zero-field value. Nonlinear Hall resistance just above Tc is attributed to magnetic impurity scattering from Eu2+ moments. The results establish PLD as a practical route to high-Tc pure-Eu nickelates and underscore that rare-earth magnetism is essential to their unusual field response.

What carries the argument

The Jaccarino–Peter (J–P) effect—paramagnetic polarization of localized Eu2+ moments that generates an internal exchange field partially compensating the external field—together with the authors’ observation that, for the underdoped x = 0.2 film, in-plane Tc at 8 T exceeds the zero-field value, forcing the conclusion that additional mechanisms beyond pure J–P compensation must operate.

What would settle it

A controlled comparison in which identical PLD-grown Nd0.7Eu0.3NiO3 precursors are reduced once by CaH2 and once by in-situ Al under otherwise identical conditions; if the CaH2 films still show markedly higher Tc and clearer field-enhanced superconductivity while structural metrics (R–P fault density, residual oxygen) remain comparable, the reduction-chemistry claim is supported; otherwise it fails.

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Extended reading notes

Core claim

PLD-synthesized Nd1-xEuxNiO2 films display a superconducting dome (0.2 ≤ x ≤ 0.5) whose optimal onset Tc ≈ 31 K at x = 0.3 exceeds that of MBE- and sputter-grown films and matches chemical synthesis, while magnetotransport shows robust field-enhanced superconductivity (under- and overdoped) and re-entrant superconductivity (x = 0.5) that cannot be fully accounted for by the Jaccarino–Peter compensation effect alone.

Load-bearing premise

The higher Tc, wider dome and field-response differences are ascribed mainly to more complete apical-oxygen removal by CaH2 gas and to high-oxygen-pressure target annealing, rather than to uncontrolled differences in stacking-fault density, residual disorder or interface chemistry that also vary across growth methods.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

2 major / 4 minor

Summary. The manuscript reports pulsed-laser-deposition growth of perovskite Nd1−xEuxNiO3 films on LSAT followed by CaH2 topotactic reduction to the infinite-layer phase over 0 ≤ x ≤ 0.7. Resistivity maps a superconducting dome for 0.2 ≤ x ≤ 0.5 with optimal onset Tc ≈ 31 K (zero-resistance 24 K) at x = 0.3, wider than prior MBE results and comparable to chemical-solution films, while magnetotransport shows field-enhanced superconductivity on both under- and over-doped sides and re-entrant superconductivity at x = 0.5. Hall data exhibit a doping-driven sign change near x = 0.3 and a nonlinear component just above Tc that is ascribed to magnetic-impurity scattering by Eu2+/Nd3+ moments; the authors conclude that PLD plus CaH2 reduction is an effective route to high-Tc Eu-doped nickelates and that Eu magnetism is essential to the observed field responses.

Significance. If the reported dome width, optimal Tc and field-induced phenomena are robust, the work supplies a practical vacuum-epitaxy route that expands the accessible doping window for pure Eu-doped infinite-layer nickelates beyond MBE and sputtering, while furnishing a clean platform for studying the interplay of rare-earth local moments with unconventional superconductivity (including possible limits of the Jaccarino–Peter compensation picture). The systematic XRD/RSM, resistivity, Hall and Hc2 data sets across the full series, together with STEM confirmation of Ruddlesden–Popper faults and a quantified Jc for the optimal film, constitute a solid experimental contribution that other groups can immediately build upon.

major comments (2)
  1. [Discussion] Discussion (paragraphs comparing synthesis routes): the central claim that PLD is “an ideal approach” because CaH2 gaseous reduction removes apical oxygen more completely than solid-state Al reduction (and because high-pO2 target annealing stabilizes the perovskite) remains correlative. The same Discussion and Fig. 1 inset already document a non-monotonic c-axis anomaly that the authors themselves attribute to enhanced Ruddlesden–Popper fault density (STEM Fig. S1). Without quantitative residual-oxygen metrics (e.g., EELS O-K edge maps) or a controlled comparison of fault density/disorder across PLD, MBE and sputtering films of identical nominal doping, the elevated Tc and wider dome could equally arise from a more favorable defect landscape. The language should be softened to “effective” and the alternative microstructural explanation acknowledged explicitly.
  2. [Fig. 4 and Results] Fig. 4(a,b) and accompanying text: for the x = 0.2 film the in-plane Tc at 8 T exceeds the zero-field value, which is used to argue that the Jaccarino–Peter effect alone is insufficient. A quantitative estimate of the exchange field HJ (or at least a comparison with the expected compensation field for the measured Eu moment density) is needed to make this claim load-bearing; otherwise the observation remains qualitative.
minor comments (4)
  1. [Figs. 1–3] Error bars on extracted Tc values, lattice constants (Fig. 1 inset) and Hall coefficients are absent; they should be added or the fitting uncertainty stated.
  2. [Results] The precise resistivity criteria used for Tconset, Tc50%ρn and Tczero should be stated once in the main text (they appear only partially in figure captions).
  3. [Throughout] Typographical inconsistencies (double subscripts such as 𝑥𝑥, occasional missing spaces around ≈ and ≤) should be cleaned throughout.
  4. [Fig. 5] Fig. 5(b) comparison would be clearer if the literature Tc values were tabulated with their exact definitions (onset vs 50 % vs zero-resistance) rather than only plotted.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: purely experimental measurements of Tc dome, Hc2, and Hall response; comparisons to other growth methods are external benchmarks, not self-defined or fitted predictions.

full rationale

The paper reports PLD synthesis of Nd1-xEuxNiO2 films, followed by CaH2 reduction, and presents measured resistivity curves (Fig. 2), Hall coefficients and nonlinear Hall resistance (Fig. 3), upper-critical-field data (Fig. 4), and the resulting doping-dependent superconducting phase diagram (Fig. 5). All quantities (onset/zero-resistance Tc values, dome width 0.2 ≤ x ≤ 0.5, optimal Tc ≈ 31 K at x = 0.3, field-enhanced and re-entrant superconductivity) are direct experimental observables extracted from transport data under stated criteria (e.g., 50 % ρn). No theoretical model is fitted to a subset of the data and then used to “predict” a related quantity; no uniqueness theorem or ansatz is imported via self-citation to force the result; lattice constants and RP-fault observations (Fig. 1, STEM) are independent structural characterizations. Citations to prior MBE, sputtering, and chemical-synthesis work supply external comparison points for dome width and Tc, not circular definitions of the present measurements. The interpretive discussion attributing higher Tc to CaH2 reduction completeness versus Al reduction is correlative commentary, not a derivation that reduces by construction to its inputs. The work is therefore self-contained and free of the enumerated circularity patterns.

Assumptions & free parameters 2 free parameters · 3 assumptions · 0 invented entities

Experimental materials paper. Load-bearing premises are standard domain assumptions of oxide thin-film growth and nickelate topotactic chemistry plus a few interpretive attributions (magnetic-impurity scattering, incomplete J-P explanation). No free parameters are fitted to produce the central Tc or dome; doping x is the controlled variable. No new microscopic entities are postulated.

free parameters (2)
  • Eu doping level x = 0–0.7 series
    Nominal composition of the PLD target; actual film stoichiometry is assumed equal to target and is not independently quantified for every x.
  • reduction temperature/time = 290 °C, 2 h
    290 °C / 2 h chosen empirically to complete apical-oxygen removal without over-reduction; not derived from first principles.
assumptions (3)
  • domain assumption CaH2 topotactic reduction converts the perovskite Nd1-xEuxNiO3 precursor into the infinite-layer Nd1-xEuxNiO2 phase while preserving epitaxial coherence.
    Standard nickelate protocol; confirmed here by XRD peak shifts and RSM, but residual apical oxygen or secondary phases cannot be ruled out by XRD alone.
  • domain assumption Eu ions are present as magnetic Eu2+ that generate an exchange field capable of partially compensating an external field (Jaccarino–Peter mechanism).
    Invoked throughout the magnetotransport discussion and in the comparison with (Sm,Eu,Ca,Sr)NiO2 literature.
  • ad hoc to paper Nonlinear Hall resistance ΔRxy just above Tc originates from magnetic impurity scattering by Eu2+/Nd3+ moments.
    Offered as a possible microscopic origin; the paper itself notes that the origin remains an open question.

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Pith. "Pith review of Superconducting dome and field-enhanced superconductivity of PLD synthesized Nd1-xEuxNiO2 thin films." pith.science (2026). https://pith.science/paper/BREXOOZL

@misc{pith2026260710332,
  author       = {Pith},
  title        = {Pith review of: Superconducting dome and field-enhanced superconductivity of PLD synthesized Nd1-xEuxNiO2 thin films},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/BREXOOZL}},
  note         = {Machine review of arXiv:2607.10332}
}
read the original abstract

We report on the synthesis of infinite-layer Nd1-xEuxNiO2 (0<x<0.7) thin films using pulsed laser deposition (PLD) followed by topotactic reduction with CaH2. Resistivity measurements on these films reveal a superconducting dome within the doping range 0.2<x<0.5, which is wider than that achieved by molecular beam epitaxy and comparable to that obtained by chemical synthesis. The x=0.3 PLD film exhibits the optimal superconducting transition temperature Tc~31 K, much higher than those grown by other vacuum epitaxial techniques. This result indicates that PLD is an ideal approach for fabricating high-quality, high-Tc Nd1-xEuxNiO2 superconducting films. Magneto-transport measurements reveal robust field-enhanced and re-entrant superconductivity in both underdoped and overdoped regimes. At low temperatures just above the onset Tc, the Hall resistance exhibits nonlinear behavior, which may originate from magnetic impurity scattering. These results highlight the crucial role of magnetic rare-earth Eu2+ ions in producing the exotic physical properties of the infinite-layer nickelates.

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Reviewed July 14, 2026 · model on record in the stance chip above.