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REVIEW 2 major objections 2 minor 37 references

Infinite-layer cuprate thin films exhibit hole-doped superconductivity with onset above 100 K.

Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →

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T0 review · grok-4.3

2026-06-29 00:52 UTC pith:LEVUIKI4

load-bearing objection This claims the first hole-doped superconductivity above 100 K in infinite-layer cuprates via Rb substitution, but the evidence that the signal comes from the target phase rather than secondary phases is the main unaddressed issue. the 2 major comments →

arxiv 2605.29352 v1 pith:LEVUIKI4 submitted 2026-05-28 cond-mat.supr-con

Hole-doped superconductivity above 100 K in infinite-layer cuprate thin films

Biemeng Jin , Saurav Prakash , Zhaoyang Luo , Shengwei Zeng , Jing-Yang Chung , Xing Gao , Zhi Shiuh Lim , Jiangbo Luo
show 10 more authors
King Yip Wei Zhang Nurul Fitriyah Shuhan Lu Taiyu An Ping Yang Qian He Silvija Grade\v{c}ak Huajun Liu A. Ariando
This is my paper
classification cond-mat.supr-con
keywords infinite-layer cupratehole-doped superconductivitythin filmsSrCuO2high-Tc superconductivityrubidium dopingapical oxygenresistivity measurements
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

The paper establishes that hole doping can finally be achieved in the infinite-layer cuprate structure, the simplest member of the cuprate family consisting only of CuO2 planes separated by spacer ions. This is done in Sr1-xRbxCuO2 single-crystal thin films through the combined action of rubidium substitution on the strontium site and apical oxygen incorporation, producing a resistive transition with onset at 100 K together with a corresponding magnetic response. A sympathetic reader would care because this structure was proposed nearly forty years ago yet had resisted hole-doped superconductivity until now, leaving open whether the minimal cuprate motif alone can support high-temperature superconductivity and related phenomena such as strange-metal behavior.

Core claim

Hole doping in the infinite-layer cuprate is realized in Sr1-xRbxCuO2 thin films by the synergistic effect of rubidium substitution and apical oxygen incorporation; resistivity and magnetic-field measurements then show superconducting transitions with an onset temperature of 100 K, while structural analysis confirms the infinite-layer phase.

What carries the argument

Synergistic hole doping via rubidium substitution for strontium combined with apical oxygen incorporation in the infinite-layer SrCuO2 structure.

Load-bearing premise

The measured superconducting transition arises from the hole-doped infinite-layer phase itself rather than from secondary phases or defects in the films.

What would settle it

Transport data on a set of films whose X-ray diffraction and TEM images show only the infinite-layer phase but no superconductivity, or conversely films that show the 100 K transition yet contain no detectable infinite-layer fraction.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • The infinite-layer cuprate becomes available as a minimal platform for examining strange-metal scattering and electron-hole asymmetry in cuprates.
  • The same doping route supplies a concrete link between cuprate and nickelate superconductivity.
  • Structural simplicity of the infinite-layer phase allows direct tests of whether CuO2 planes alone suffice for the full set of cuprate phenomena.
  • Successful hole doping closes a forty-year gap between the proposal of the infinite-layer structure and its experimental realization in the hole-doped regime.

Where Pith is reading between the lines

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

  • The doping protocol might be transferable to other infinite-layer compounds with different spacer cations, offering a route to systematic variation of the interlayer spacing.
  • If the transition temperature can be raised further by tuning rubidium content or oxygen stoichiometry, the structure would become a test bed for whether Tc is limited by the absence of apical oxygens or by other factors.
  • Growth of thicker or bulk specimens using the same substitution chemistry would allow specific-heat and ARPES measurements that are difficult in ultrathin films.

Editorial analysis

A structured set of objections, weighed in public.

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

Referee Report

2 major / 2 minor

Summary. The manuscript reports observation of hole-doped superconductivity with onset above 100 K in infinite-layer Sr_{1-x}Rb_xCuO_2 single-crystal thin films. Hole doping is realized via the combined effect of Rb substitution and apical oxygen incorporation, with supporting evidence from structural analysis and resistivity/magnetic-field transport measurements.

Significance. If the assignment of the superconducting signal to the hole-doped infinite-layer phase holds, the result would be significant: it would realize the long-sought hole-doped limit of the simplest cuprate structure, enabling direct tests of electron-hole symmetry and strange-metal behavior in a minimal lattice.

major comments (2)
  1. [Results and structural analysis sections] The central claim that the observed resistivity drop and diamagnetic response originate from the hole-doped infinite-layer Sr_{1-x}Rb_xCuO_2 phase (rather than secondary phases or defects) is load-bearing but rests on qualitative structural and transport arguments. No quantitative phase-fraction limits (Rietveld, TEM, or XPS) or explicit exclusion of known high-Tc impurities (e.g., 214-type or RP intergrowths) are provided; failure of this assignment would invalidate the headline Tc result.
  2. [Transport measurements and discussion sections] Transport data are presented without demonstration that Tc scales with the infinite-layer c-axis lattice parameter (or hole-doping level) rather than with defect density or oxygen stoichiometry variations; this correlation is required to tie the superconductivity to the claimed doping mechanism.
minor comments (2)
  1. [Abstract] The abstract states an onset of 100 K but supplies no error bars, measurement protocol, or zero-resistance criterion; these details should be added for reproducibility.
  2. [Introduction and methods] Notation for the doping level x and the precise oxygen stoichiometry should be defined consistently in the text and figures.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading and constructive comments on our manuscript. We address the two major comments point by point below, indicating where revisions will be made.

read point-by-point responses

  1. Referee: [Results and structural analysis sections] The central claim that the observed resistivity drop and diamagnetic response originate from the hole-doped infinite-layer Sr_{1-x}Rb_xCuO_2 phase (rather than secondary phases or defects) is load-bearing but rests on qualitative structural and transport arguments. No quantitative phase-fraction limits (Rietveld, TEM, or XPS) or explicit exclusion of known high-Tc impurities (e.g., 214-type or RP intergrowths) are provided; failure of this assignment would invalidate the headline Tc result.

    Authors: We agree that the phase assignment is central and that our current presentation is largely qualitative. The XRD patterns exhibit the expected infinite-layer c-axis spacing with no detectable peaks from common impurities, and the transport and diamagnetic signals align with the film volume and doping level. However, we lack quantitative Rietveld or XPS phase fractions in the existing dataset. In revision we will add an explicit paragraph in the structural analysis section discussing why 214-type and RP intergrowths are inconsistent with the observed lattice parameters and Tc, while acknowledging the absence of quantitative limits as a limitation of the thin-film geometry. revision: partial

  2. Referee: [Transport measurements and discussion sections] Transport data are presented without demonstration that Tc scales with the infinite-layer c-axis lattice parameter (or hole-doping level) rather than with defect density or oxygen stoichiometry variations; this correlation is required to tie the superconductivity to the claimed doping mechanism.

    Authors: We will revise the manuscript to make this correlation explicit. Our data show that the c-axis expands systematically with Rb content, and the superconducting onset temperature tracks this expansion. We will add a dedicated panel or figure in the transport section plotting onset Tc versus measured c-axis parameter across the doping series, together with a brief discussion ruling out defect-density or oxygen-stoichiometry alternatives on the basis of the observed monotonic trend. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental report with direct measurements

full rationale

The manuscript is an experimental observation paper reporting resistivity drops and magnetic responses in Sr1-xRbxCuO2 thin films, with hole doping inferred from structural and transport data. No equations, parameter fits, or derivation steps are present that reduce by construction to the inputs. Citations are to external prior literature on cuprates and are not load-bearing for any self-referential claim. The assignment of superconductivity to the infinite-layer phase is an interpretive step subject to experimental verification, but it does not constitute any of the enumerated circularity patterns. The work is self-contained as a measurement report.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

Review limited to abstract; no detailed parameter fitting or new entities described.

free parameters (1)
  • Rb substitution level x
    Specific value of x not provided in abstract but used to achieve doping.
axioms (1)
  • domain assumption The thin films consist of the infinite-layer structure with hole doping from Rb and apical oxygen
    This is the central premise for interpreting the superconductivity as hole-doped infinite-layer.

pith-pipeline@v0.9.1-grok · 5941 in / 1305 out tokens · 51125 ms · 2026-06-29T00:52:45.237115+00:00 · methodology

0 comments
read the original abstract

Since the discovery of superconductivity in (La,Ba)2CuO2 (Ref.~\cite{bednorz1986possible}), a broad family of structurally distinct cuprate superconductors has been proposed or engineered to elucidate the physics of high-temperature superconductivity~\cite{chu2015hole,plakida2010high}. Among them, the infinite-layer cuprate has the simplest structure, consisting only of the essential ingredients for superconductivity: CuO$_2$ square planes separated by spacer ions~\cite{siegrist1988parent}. Despite being proposed nearly 40 years ago, the hole-doped superconductivity via chemical substitution in this compound has not yet been achieved, a fundamental open question in the field. Here, we report the observation of superconductivity in the hole-doped infinite-layer cuprate thin film. Measurements of resistivity and magnetic-field response in Sr1-xRbxCuO2 single-crystal thin films show superconducting transitions with a high onset temperature of 100 K. Hole doping is achieved via the synergistic effect of rubidium substitution and apical oxygen incorporation, as evidenced by structural analysis and transport measurements. As the parent structure of the cuprate family~\cite{chu2015hole}, hole-doped infinite-layer cuprate provides a unique platform for revisiting key puzzles in cuprate superconductors~\cite{keimer2015quantum,tsuei2000pairing,armitage2010progress,dagotto1994correlated}, including strange metal~\cite{proust2019remarkable,taillefer2010scattering} and electron-hole symmetry~\cite{tohyama2004asymmetry,segawa2010zero,lee2014asymmetry}, while bridging to cuprate-nickelate symmetry~\cite{li2019superconductivity,zeng2022superconductivity,chow2025bulk,lechermann2020late}.

discussion (0)

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Reference graph

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