Bulk superconductivity up to 96 K in pressurized nickelate single crystals

Di Peng; Feiyu Li; Hirokazu Kadobayashi; Jian Zhang; Jie Dou; Jie Yang; Jinguang Cheng; Junjie Zhang; Jun Luo; Liang Ma

arxiv: 2501.14584 · v3 · submitted 2025-01-24 · ❄️ cond-mat.supr-con · cond-mat.mtrl-sci· cond-mat.str-el

Bulk superconductivity up to 96 K in pressurized nickelate single crystals

Feiyu Li , Zhenfang Xing , Di Peng , Jie Dou , Ning Guo , Liang Ma , Yulin Zhang , Lingzhen Wang

show 19 more authors

Jun Luo Jie Yang Jian Zhang Tieyan Chang Yu-Sheng Chen Weizhao Cai Jinguang Cheng Yuzhu Wang Yuxin Liu Tao Luo Naohisa Hirao Takahiro Matsuoka Hirokazu Kadobayashi Zhidan Zeng Qiang Zheng Rui Zhou Qiaoshi Zeng Xutang Tao Junjie Zhang

This is my paper

Pith reviewed 2026-05-23 05:33 UTC · model grok-4.3

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

keywords nickelate superconductorsbulk superconductivityhigh pressuresingle crystalsLa2SmNi2O7Ruddlesden-Popper phasetransition temperaturelattice distortion

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The pith

Bilayer nickelate single crystals show bulk superconductivity up to 96 K under pressure.

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

The paper reports that La2SmNi2O7-δ single crystals grown by flux method at ambient pressure display intrinsic bulk superconductivity when pressurized. Zero electrical resistance appears with onset at 92 K and complete zero at 73 K at 21.6 GPa, accompanied by a Meissner effect at 60 K. Structural measurements show that both monoclinic and tetragonal phases support the superconducting state, and Tc rises with greater in-plane lattice distortion measured at ambient pressure. A related composition reaches 96 K onset. The work demonstrates an ambient-pressure route to high-quality nickelate crystals and a correlation that points toward higher transition temperatures.

Core claim

La2SmNi2O7-δ bilayer nickelate single crystals, synthesized at ambient pressure, exhibit bulk superconductivity under high pressure with a maximum onset Tc of 92 K (zero resistivity at 73 K at 21.6 GPa) and Meissner Tc of 60 K at 20.6 GPa; a related La1.57Sm1.43Ni2O7-δ composition reaches 96 K onset. Both monoclinic and tetragonal structures sustain the superconducting state, and higher Tc correlates with larger ambient-pressure in-plane lattice distortion.

What carries the argument

Pressure-induced bulk superconductivity in flux-grown La2SmNi2O7-δ crystals, tied to ambient in-plane lattice distortion.

If this is right

Ambient-pressure flux growth yields reproducible nickelate crystals that superconduct under pressure.
Both monoclinic and tetragonal phases can host superconductivity in this bilayer nickelate.
Tc increases with larger in-plane lattice distortion at ambient conditions.
Compositional tuning of rare-earth content can push onset Tc above 92 K.
The distortion-Tc correlation supplies a practical design rule for targeting higher transition temperatures.

Where Pith is reading between the lines

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

The same distortion-tuning strategy might be tested in other Ruddlesden-Popper nickelates or related layered oxides.
If the correlation proves causal, modest chemical pressure or strain at ambient conditions could reduce the external pressure needed for superconductivity.
Single-crystal data under pressure now allow direct comparison with theoretical models that assume specific lattice symmetries.
Repeating the growth and pressure protocol on larger crystals would test whether the reported Tc values scale with sample volume.

Load-bearing premise

The zero-resistivity and diamagnetic signals measured under pressure arise from the nickelate crystal volume rather than from filamentary paths or pressure-induced defects.

What would settle it

Absence of a bulk Meissner effect or zero resistivity in additional high-quality crystals of the same composition under 20 GPa, despite confirmed phase purity by XRD and NQR, would falsify the bulk superconductivity claim.

read the original abstract

Recently, the Ruddlesden-Popper bilayer nickelate $La_3Ni_2O_7$ has emerged as a superconductor with a transition temperature ($T_c$) of approximately 80 K above 14 GPa (Refs. 1-3). Achieving higher $T_c$ in nickelate superconductors, along with the synthesis of reproducible high-quality single crystals without relying on high-oxygen-pressure growth conditions, remains a significant challenge$^{[4-7]}$. Here we report superconductivity up to 96 K under high pressure in bilayer nickelate single crystals synthesized at ambient pressure. Energy-dispersive spectroscopy, single-crystal X-ray diffraction, nuclear quadrupole resonance and scanning transmission electron microscopy evidenced high crystal quality of the flux-grown $La_2SmNi_2O_{7-{\delta}}$ single crystals. $La_2SmNi_2O_7$ exhibits clear bulk superconductivity, including zero resistivity ($T_{c,max}^{onset}$ = 92 K and $T_{c,max}^{zero}$ = 73 K at 21.6 GPa) and the Meissner effect ($T_c$= 60 K at 20.6 GPa). A low-temperature high-pressure structural study indicates that both monoclinic and tetragonal structures can support superconductivity in this bilayer nickelate. Furthermore, we established a correlation between higher $T_c$ under high pressures and larger in-plane lattice distortion under ambient conditions, corroborated by observing even higher $T_c^{onset}$ of 96 K in $La_{1.57}Sm_{1.43}Ni_2O_{7-{\delta}}$. This study overcomes key limitations in growing nickelate superconductor crystals, resolves the crystal structure in the superconducting state and demonstrates an effective pathway towards achieving higher $T_c$.

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

They grew ambient-pressure nickelate crystals that reach 96 K onset under pressure, but the bulk claim rests on zero resistance and a modest Meissner signal without volume-fraction data.

read the letter

The new result here is flux-grown La2SmNi2O7 and La1.57Sm1.43Ni2O7-δ single crystals that show superconductivity under pressure, with onset reaching 96 K and zero resistance at 73 K. The synthesis route is the practical advance: these crystals were made at ambient pressure instead of the high-oxygen-pressure methods that have limited the field so far. The structural work under pressure is also useful; they resolve both monoclinic and tetragonal phases in the superconducting regime and tie higher Tc to larger ambient in-plane distortion across the two compositions they measured. Characterizations (EDS, single-crystal XRD, NQR, STEM) look standard and adequate for confirming stoichiometry and crystal quality on the samples they report. That combination of easier growth plus a new Tc record inside the bilayer nickelate family is the part worth noting. The soft spot is the evidence that the superconductivity is bulk rather than filamentary. The abstract gives zero resistivity at 21.6 GPa and a Meissner transition at 60 K at 20.6 GPa, but the 30-plus-K spread between onset, zero resistance, and diamagnetic onset is exactly the pattern that appears when only a small volume fraction is superconducting. No shielding fraction or diamagnetic volume is mentioned, and high-pressure cells often produce percolating paths that give zero resistance without bulk behavior. The lattice-distortion correlation does not fix that gap. This paper is for groups already working on pressurized nickelates or looking for new crystal-growth routes in the family. It is coherent on its own terms and engages the recent La3Ni2O7 literature directly, so it deserves referee time even though the volume-fraction question will need addressing in revision. I would send it out rather than desk-reject.

Referee Report

2 major / 2 minor

Summary. The manuscript claims discovery of bulk superconductivity up to 96 K in ambient-pressure flux-grown La2SmNi2O7 single crystals under pressure, with zero resistivity (onset 92 K, zero-resistance 73 K at 21.6 GPa) and Meissner effect (60 K at 20.6 GPa) in La2SmNi2O7, plus higher onset in a related composition. It reports high crystal quality via EDS, single-crystal XRD, NQR and STEM, a pressure-dependent structural study showing both monoclinic and tetragonal phases can support superconductivity, and a correlation between higher Tc and larger ambient in-plane lattice distortion.

Significance. If the superconductivity is confirmed as intrinsic and bulk (majority volume fraction), the work would advance the nickelate field by achieving Tc higher than prior ~80 K reports, using accessible ambient-pressure crystal growth instead of high-oxygen-pressure methods, and supplying high-pressure structural data that resolves the superconducting-state structure. The reported lattice-distortion correlation, if quantitatively supported, could provide a useful design handle for further Tc increases.

major comments (2)

[Abstract] Abstract: The assertion of 'clear bulk superconductivity' rests on zero resistivity and a Meissner signal, yet the ~32 K spread between Tc,onset (92 K), Tc,zero (73 K) and Meissner Tc (60 K) is left unaddressed; no diamagnetic volume fraction is reported from the magnetization data. In diamond-anvil-cell experiments this spread is consistent with filamentary rather than uniform bulk superconductivity, and the listed crystal-quality diagnostics (EDS, XRD, NQR, STEM) do not quantify the superconducting volume fraction.
[Abstract] Abstract: The claim that 'both monoclinic and tetragonal structures can support superconductivity' is presented without specifying how the structural phase was assigned at the pressures where superconductivity is observed, or whether the resistivity/Meissner data were taken on samples confirmed to be in one phase versus the other.

minor comments (2)

[Abstract] Abstract: Inconsistent chemical notation (La2SmNi2O7 versus La_{1.57}Sm_{1.43}Ni2O_{7-δ}); subscripts and the oxygen deficiency symbol should be standardized.
[Abstract] Abstract: The Meissner Tc is stated as 60 K without clarifying whether this is an onset, midpoint, or other convention, and without direct comparison to the resistivity transition temperatures on the same sample.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful and constructive review of our manuscript. We address each major comment point by point below, providing clarifications and indicating where revisions will be made.

read point-by-point responses

Referee: [Abstract] Abstract: The assertion of 'clear bulk superconductivity' rests on zero resistivity and a Meissner signal, yet the ~32 K spread between Tc,onset (92 K), Tc,zero (73 K) and Meissner Tc (60 K) is left unaddressed; no diamagnetic volume fraction is reported from the magnetization data. In diamond-anvil-cell experiments this spread is consistent with filamentary rather than uniform bulk superconductivity, and the listed crystal-quality diagnostics (EDS, XRD, NQR, STEM) do not quantify the superconducting volume fraction.

Authors: We acknowledge the spread between the reported transition temperatures and agree that it merits explicit discussion. In diamond-anvil-cell experiments, pressure inhomogeneities and non-hydrostatic conditions frequently produce broadened transitions even for samples exhibiting bulk superconductivity. The observation of a zero-resistance state demonstrates a percolating superconducting pathway through the crystal, while the Meissner effect provides direct evidence of diamagnetism. Although a quantitative diamagnetic volume fraction is not reported—owing to the small sample size and technical constraints of magnetization measurements inside a DAC—the combination of zero resistivity, diamagnetic response, and multiple independent probes of crystal quality (EDS, single-crystal XRD, NQR, and STEM) supports the interpretation of bulk superconductivity. We will revise the manuscript to include a dedicated discussion of the transition-width issue and its relation to pressure conditions. revision: partial
Referee: [Abstract] Abstract: The claim that 'both monoclinic and tetragonal structures can support superconductivity' is presented without specifying how the structural phase was assigned at the pressures where superconductivity is observed, or whether the resistivity/Meissner data were taken on samples confirmed to be in one phase versus the other.

Authors: The low-temperature high-pressure structural study was performed on crystals from the same growth batches and under pressure-temperature conditions that overlap with those used for the resistivity and magnetization measurements. Phase identification (monoclinic versus tetragonal) was obtained from single-crystal XRD patterns collected at low temperature under applied pressure. We will revise the relevant sections to explicitly describe the phase-assignment procedure and to state that the transport and magnetic data were acquired on samples whose structures were verified under comparable conditions, thereby substantiating that superconductivity occurs in both phases. revision: yes

Circularity Check

0 steps flagged

No circularity: purely experimental report with no derivations or self-referential fits

full rationale

This is an experimental paper reporting direct measurements (resistivity, Meissner effect, XRD, NQR, STEM) on flux-grown crystals under pressure. No equations, fitted parameters, or predictions are defined in terms of the target Tc values. No self-citation load-bearing steps or uniqueness theorems appear. Central claims rest on raw data and standard characterization, not on any reduction to inputs by construction. Score 0 is the appropriate finding for self-contained experimental work.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on standard experimental techniques in high-pressure condensed-matter physics rather than new theoretical postulates; no free parameters or invented entities are introduced in the abstract.

axioms (1)

domain assumption High-pressure resistivity and magnetization measurements accurately reflect intrinsic sample properties when crystal quality is confirmed by EDS, XRD, NQR and STEM.
Implicit in the interpretation of zero resistivity and Meissner effect as bulk superconductivity.

pith-pipeline@v0.9.0 · 5978 in / 1517 out tokens · 74331 ms · 2026-05-23T05:33:41.036860+00:00 · methodology

discussion (0)

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Relation between the paper passage and the cited Recognition theorem.

La2SmNi2O7 exhibits clear bulk superconductivity, including zero resistivity (Tc,max onset = 92 K and Tc,max zero = 73 K at 21.6 GPa) and the Meissner effect (Tc = 60 K at 20.6 GPa).

What do these tags mean?

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supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Forward citations

Cited by 3 Pith papers

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DFT-based tight-binding models and FRG calculations predict that reducing in-plane lattice constant or increasing out-of-plane constant in La3Ni2O7 films increases Fermi-level DOS and enhances Tc while preserving s± pairing.