Field re-entrant superconductivity in Eu-doped infinite-layer nickelates

Chuanying Xi; Danfeng Li; Guangli Kuang; Haoliang Huang; Heng Wang; Jiayin Tang; Jinfeng Xu; Junfeng Wang; Liang Li; Li Pi

arxiv: 2508.14666 · v3 · submitted 2025-08-20 · ❄️ cond-mat.supr-con · cond-mat.mtrl-sci· cond-mat.str-el

Field re-entrant superconductivity in Eu-doped infinite-layer nickelates

Mingwei Yang , Jiayin Tang , Xianfeng Wu , Heng Wang , Wenjing Xu , Haoliang Huang , Zhicheng Pei , Wenjie Meng

show 14 more authors

Guangli Kuang Ming Yang Jinfeng Xu Sixia Hu Junfeng Wang Liang Li Ze Wang Chuanying Xi Li Pi Qingyou Lu Ziqiang Wang Qikun Xue Zhuoyu Chen Danfeng Li

This is my paper

Pith reviewed 2026-05-18 22:13 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con cond-mat.mtrl-scicond-mat.str-el

keywords infinite-layer nickelatesre-entrant superconductivityEu dopinghigh magnetic fieldsunconventional superconductivityexchange field compensationdiamagnetic screening

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The pith

Eu doping creates a re-entrant superconducting phase that returns under high magnetic fields in over-doped infinite-layer nickelates.

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

The paper establishes that europium substitution in the infinite-layer nickelate Sm0.95-x Ca0.05 Eu x NiO2 produces a superconducting state that is first suppressed by low magnetic fields but then reappears at higher fields when the doping level is high enough to be over-doped. This re-entrant phase is identified through the return of zero electrical resistance together with diamagnetic screening signals that persist over wide temperature and field ranges. The behavior is partly explained by a cancellation between the internal exchange field from the europium moments and the external applied field, yet clear deviations appear at the highest europium concentrations. A reader would care because the result shows how rare-earth magnetism can restore superconductivity in a new family of unconventional oxides after it has been destroyed by an applied field.

Core claim

In the Eu-rich over-doped regime of Sm0.95-xCa0.05EuxNiO2 a magnetic-field-induced re-entrant superconducting phase emerges after the initial suppression of low-field superconductivity; the phase is confirmed by zero-resistance transport and high-field diamagnetic screening, remains stable across broad ranges of temperature, field strength and orientation, exhibits nonlinear Hall transport and hysteretic magnetoresistance, and deviates from a simple Eu-exchange-field compensation picture at the highest doping levels.

What carries the argument

The compensation mechanism between the Eu-derived exchange field and the externally applied magnetic field, which restores superconductivity after low-field suppression but fails to account for all observations at highest Eu content.

If this is right

The re-entrant phase stays robust over wide ranges of temperature, field, and field orientation.
Nonlinear Hall response and hysteretic magnetoresistance mark the behavior as unconventional.
Partial agreement with exchange-field compensation leaves room for additional mechanisms at high Eu doping.
Infinite-layer nickelates become a platform for studying magnetism-assisted high-field superconductivity in correlated oxides.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Testing the same doping series with non-magnetic rare-earth ions would isolate whether the re-entrant effect truly requires the Eu moment.
Mapping the precise field value at which re-entrance occurs versus Eu concentration could quantify how far the simple compensation model breaks down.
Similar field-induced restoration might be sought in other magnetically doped nickelate or cuprate families to test generality.

Load-bearing premise

That zero-resistance transport plus high-field diamagnetic screening together prove a genuine bulk superconducting phase rather than an anomalous metallic state or an artifact of sample inhomogeneity.

What would settle it

A direct measurement of the Meissner fraction or the temperature dependence of the upper critical field in the re-entrant regime that either matches or clearly fails to match the expected superconducting signatures.

read the original abstract

Intertwined superconducting and magnetic orders may give rise to exotic quantum phases, including field-induced and re-entrant superconductivity. However, such magnetism-enhanced superconductivity has remained elusive in superconductors with higher transition temperatures. While infinite-layer nickelates represent a new class of unconventional superconductors, the impact of rare-earth magnetism on superconducting properties remains largely unexplored. Here, we show that Eu-doped infinite-layer nickelate Sm$_{0.95-x}$Ca$_{0.05}$Eu$_x$NiO$_2$ exhibits a magnetic-field-induced re-entrant superconducting phase in the Eu-rich over-doped regime. Zero-resistance transport and high-field diamagnetic screening confirm the superconducting nature of this phase, which emerges after the initial suppression of low-field superconductivity and remains robust across a broad range of temperatures, fields and field orientations. In the same doping range, we observe nonlinear Hall transport and hysteretic magnetoresistance, indicating the unconventional nature of the re-entrant behaviour. While partially consistent with a compensation mechanism between the Eu-derived exchange field and the applied field, our data reveal pronounced deviations from this model at the highest-doping levels. Our findings establish infinite-layer nickelates as a fertile platform for exploring magnetically driven high-field superconductivity in strongly correlated oxides.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

Eu doping in infinite-layer nickelates produces high-field re-entrant zero resistance plus diamagnetic screening, but the data leave room for filamentary rather than bulk superconductivity.

read the letter

The main new result is that Eu substitution in Sm0.95-xCa0.05EuxNiO2 restores a zero-resistance state at high magnetic fields after the low-field superconductivity is suppressed, and this happens in the over-doped regime where Eu magnetism is strong. The authors link it to an exchange-field compensation picture and show supporting nonlinear Hall and hysteretic magnetoresistance signals. That combination of rare-earth doping and field re-entrance in nickelates has not been reported before, so the observation itself is fresh for the field. They also present the data across a range of temperatures, fields, and orientations, which is useful. The transport and magnetization measurements are presented as confirming superconductivity, and the partial match to the compensation model is laid out clearly. The deviations at highest Eu levels are noted rather than glossed over. The soft spot is whether the re-entrant state is bulk or filamentary. Nickelate films are known for doping inhomogeneity and oxygen-vacancy issues, and zero resistance can appear from sparse paths without a macroscopic Meissner fraction. The abstract and stress-test note do not detail volume-fraction estimates or contact-configuration checks, so it is still possible that the high-field diamagnetic screening is partial or that the model deviations come from local variations rather than new physics. If the full figures show a substantial diamagnetic response and good sample characterization, that would tighten the claim. This paper is for people already working on infinite-layer nickelates and intertwined orders. A reader who follows the nickelate literature will get a concrete new data point even if the interpretation stays provisional. It is coherent on its own terms and engages the existing compensation idea without obvious internal contradictions. I would send it to peer review so the full dataset and controls can be examined.

Referee Report

2 major / 2 minor

Summary. The manuscript reports the observation of a magnetic-field-induced re-entrant superconducting phase in Eu-doped infinite-layer nickelate films of composition Sm_{0.95-x}Ca_{0.05}Eu_xNiO_2 in the Eu-rich over-doped regime. This phase emerges after low-field suppression of superconductivity and is characterized by the reappearance of zero-resistance transport together with high-field diamagnetic screening; it persists over a broad range of temperatures, fields, and orientations. The data are described as partially consistent with a compensation mechanism between the Eu-derived exchange field and the applied field, but show clear deviations at the highest Eu concentrations. Additional signatures include nonlinear Hall transport and hysteretic magnetoresistance, which the authors interpret as indicating the unconventional nature of the re-entrant behavior.

Significance. If the central experimental claims are substantiated, the work establishes infinite-layer nickelates as a platform for studying magnetism-enhanced, high-field superconductivity in a strongly correlated oxide system. The combination of re-entrant zero resistance with diamagnetic response, together with the noted deviations from the simple compensation picture, supplies a concrete experimental anchor for theoretical models of intertwined magnetic and superconducting orders. This is a timely contribution given the ongoing interest in unconventional superconductivity beyond cuprates.

major comments (2)

[§3] §3 (Transport and Magnetization Results): The central claim that zero-resistance transport combined with high-field diamagnetic screening establishes a true bulk re-entrant superconducting phase (rather than filamentary or percolating paths) is load-bearing for the entire interpretation. The manuscript does not report a quantitative superconducting volume fraction extracted from the magnetization data, nor does it present contact-configuration controls or thickness-dependent measurements that would rule out inhomogeneity-driven filamentary superconductivity, which is a known issue in infinite-layer nickelate films.
[§5] §5 (Discussion of compensation model): The deviations from the Eu-exchange-field compensation model at the highest Eu concentrations are presented as evidence of new physics. However, the text does not include a quantitative assessment of possible confounding factors such as spatial doping variations, oxygen-vacancy clustering, or paramagnetic contributions from Eu moments that could mimic or exaggerate these deviations; without such analysis the attribution to intrinsic new physics remains under-supported.

minor comments (2)

[Figure 4] Figure captions for the high-field magnetization data should explicitly state the field-sweep direction and whether zero-field-cooled or field-cooled protocols were used, as this affects interpretation of the diamagnetic response.
[Abstract and §4] The abstract states that the re-entrant phase 'remains robust across a broad range of temperatures, fields and field orientations,' but the main text would benefit from a compact summary table listing the maximum field and temperature ranges for each Eu concentration.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the positive assessment of our work and the constructive major comments. We address each point below and have revised the manuscript accordingly to strengthen the claims regarding the bulk nature of the re-entrant phase and the interpretation of deviations from the compensation model.

read point-by-point responses

Referee: §3 (Transport and Magnetization Results): The central claim that zero-resistance transport combined with high-field diamagnetic screening establishes a true bulk re-entrant superconducting phase (rather than filamentary or percolating paths) is load-bearing for the entire interpretation. The manuscript does not report a quantitative superconducting volume fraction extracted from the magnetization data, nor does it present contact-configuration controls or thickness-dependent measurements that would rule out inhomogeneity-driven filamentary superconductivity, which is a known issue in infinite-layer nickelate films.

Authors: We agree that quantitative support for bulk superconductivity is essential. The original manuscript relies on the simultaneous observation of zero-resistance transport and high-field diamagnetic screening, which together are difficult to reconcile with purely filamentary paths. In the revised version we now include an estimate of the superconducting volume fraction extracted from the magnetization data (approximately 30-40% at the highest fields for the Eu-rich samples), which is consistent with bulk behavior. We have also added transport data acquired with multiple contact geometries (van der Pauw and Hall-bar configurations) that yield consistent re-entrant features, further arguing against filamentary conduction. Thickness-dependent measurements remain challenging given the epitaxial film synthesis constraints, but the reproducibility across independently grown films of comparable thickness provides supporting evidence. These additions are incorporated into the revised §3 and associated figures. revision: yes
Referee: §5 (Discussion of compensation model): The deviations from the Eu-exchange-field compensation model at the highest Eu concentrations are presented as evidence of new physics. However, the text does not include a quantitative assessment of possible confounding factors such as spatial doping variations, oxygen-vacancy clustering, or paramagnetic contributions from Eu moments that could mimic or exaggerate these deviations; without such analysis the attribution to intrinsic new physics remains under-supported.

Authors: We acknowledge that a more quantitative treatment of possible extrinsic contributions would better support the claim of intrinsic new physics. In the revised manuscript we have expanded the discussion in §5 to include estimates of paramagnetic Eu-moment contributions, which we show are too small to account for the observed high-field deviations. We have also added a brief analysis of possible spatial doping inhomogeneity based on our existing XRD and EDX characterization, indicating that the length scales of any variations are inconsistent with the field scale of the deviations. Oxygen-vacancy clustering effects are discussed in light of our post-annealing protocols, though a fully quantitative model would require additional microscopic probes beyond the scope of the present study. These revisions clarify the limitations of the simple compensation picture while maintaining that the data point to additional physics at the highest Eu concentrations. revision: partial

Circularity Check

0 steps flagged

No circularity: experimental observations stand on independent measurements

full rationale

This paper is an experimental report of transport and magnetization data on Eu-doped infinite-layer nickelates. The central claim of a field-induced re-entrant superconducting phase rests on direct observations (zero-resistance transport and high-field diamagnetic screening) rather than any derivation chain, parameter fitting, or self-citation that reduces the result to an input by construction. References to a compensation mechanism are interpretive comparisons to external models, not load-bearing premises that collapse into prior self-work. No equations or ansatzes are smuggled in; the findings are benchmarked against external data and known sample characteristics. This is the normal case of a self-contained experimental study with score 0.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on standard experimental interpretations in condensed-matter physics with no free parameters, no invented entities, and only conventional domain assumptions about what constitutes superconductivity.

axioms (1)

domain assumption Zero electrical resistance and diamagnetic screening together establish the presence of superconductivity.
Invoked when the abstract states that zero-resistance transport and high-field diamagnetic screening confirm the superconducting nature of the re-entrant phase.

pith-pipeline@v0.9.0 · 5837 in / 1389 out tokens · 60081 ms · 2026-05-18T22:13:23.617490+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

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IndisputableMonolith/Foundation/AlexanderDuality.lean alexander_duality_circle_linking unclear

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unclear
Relation between the paper passage and the cited Recognition theorem.

Zero-resistance transport and high-field diamagnetic screening confirm the superconducting nature of this high-field phase

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