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arxiv: 2606.03981 · v1 · pith:JVMZ7JDCnew · submitted 2026-06-02 · ❄️ cond-mat.supr-con · cond-mat.str-el

Bipolar-doped superconducting infinite-layer cuprates

Fengzhe Wang , Yueying Li , Heng Wang , Lizhi Xu , Xianfeng Wu , Lixiang Xu , Guangdi Zhou , Jin-Feng Jia
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Peng Li Haoliang Huang Qi-Kun Xue Zhuoyu Chen
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Pith reviewed 2026-06-28 07:54 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con cond-mat.str-el
keywords infinite-layer cupratesbipolar dopingantiferromagnetic foldingFermi arcsARPEShigh-Tc superconductivitythin filmsLuttinger volume
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The pith

Bipolar doping in infinite-layer cuprate films produces antiferromagnetic band folding from Fermi arcs at hole doping of ~0.07 with superconducting onset above 60 K.

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

The work synthesizes single-crystalline thin films of infinite-layer cuprates that can be doped controllably with either electrons or holes, removing the usual charge-reservoir layers. Angle-resolved photoemission spectroscopy across the resulting phase diagram shows that antiferromagnetic band folding remains visible even where superconductivity appears. At the specific hole doping level of approximately 0.07 fixed by the Luttinger volume of a single Fermi surface, the folding signal grows out of the Fermi arcs while the onset transition temperature exceeds 60 K. This observation supplies a cleaner experimental window onto the CuO2 plane itself.

Core claim

Bipolar doping is achieved in (Sr,Eu)CuO2 and (Ca,Li)CuO2+δ infinite-layer films. ARPES reveals persistent antiferromagnetic band folding that coexists with superconductivity in both doping regimes. At hole doping ~0.07 set by the Luttinger volume, the folding emerges directly from the Fermi arcs of the film’s single Fermi surface, and the superconducting onset temperature exceeds 60 K.

What carries the argument

Luttinger-volume determination of hole doping combined with ARPES detection of antiferromagnetic band folding that originates from Fermi arcs inside a single Fermi surface.

If this is right

  • Electrical resistance shows strong in-plane versus out-of-plane anisotropy consistent with quasi-two-dimensional CuO2 planes in both electron- and hole-doped films.
  • Antiferromagnetic band folding coexists with superconductivity across the entire accessible doping range.
  • The single-Fermi-surface topology at low hole doping supplies a reference point for mapping the intrinsic phase diagram of the CuO2 plane.
  • The platform removes the structural complexity of charge-reservoir layers that has historically complicated spectroscopic studies.

Where Pith is reading between the lines

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

  • If the observed folding truly tracks the same antiferromagnetic order that appears in other cuprate families, the result would imply that this order survives to higher doping levels than previously mapped in hole-doped systems.
  • The ability to reach both sides of the phase diagram in the same infinite-layer structure could allow direct comparison of electron-hole asymmetry without changes in crystal structure.
  • Extension of the same film-growth approach to other rare-earth substitutions might isolate the role of apical-oxygen distance while keeping the doping method fixed.

Load-bearing premise

The hole doping level extracted from the Luttinger volume of the ARPES Fermi surface accurately reflects the bulk carrier density without significant distortion from surface reconstruction, disorder, or non-Fermi-surface contributions.

What would settle it

Direct measurement of the actual hole density (for example by Hall effect or chemical titration) that deviates substantially from the Luttinger volume value of 0.07 while the antiferromagnetic folding signal is absent or appears at a different doping.

read the original abstract

Distilling the intrinsic physics of the superconducting CuO2 plane from the complexities of charge-reservoir layers is a defining challenge in high-temperature superconductivity. While superconducting electron-doped infinite-layer cuprates have been synthesized, controllable and uniform hole doping has long remained elusive despite exploratory attempts, limiting spectroscopic insights. Here, we realize bipolar doping across infinite-layer (Sr,Eu)CuO2 and (Ca,Li)CuO2+{\delta} single-crystalline thin films, mapping the electronic phase diagram. Both electron- and hole-doped films show pronounced electrical resistance anisotropy, indicating the quasi-two-dimensional nature of the CuO2 planes. Angle-resolved photoemission spectroscopy across electron- and hole-doped regimes reveals persistent antiferromagnetic band folding coexisting with superconductivity. Remarkably, at a hole doping ~0.07 determined by Luttinger volume, the antiferromagnetic folding emerges from Fermi arcs within the film's single Fermi surface, with the onset superconducting transition temperature exceeding 60 K. These findings redefine the interplay between magnetic order and superconductivity and establish a definitive platform to investigate the intrinsic mechanism of high-temperature superconducting cuprates.

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.

Referee Report

3 major / 2 minor

Summary. The manuscript reports synthesis of bipolar-doped infinite-layer cuprate thin films ((Sr,Eu)CuO2 and (Ca,Li)CuO2+δ) and ARPES measurements showing persistent antiferromagnetic band folding coexisting with superconductivity in both electron- and hole-doped regimes. The central claim is that at hole doping p~0.07 (extracted via Luttinger volume from a single Fermi surface), AF folding emerges from Fermi arcs, with onset Tc exceeding 60 K.

Significance. If the doping calibration and surface-bulk correspondence are validated, the work supplies a new platform for isolating the intrinsic CuO2-plane physics across the phase diagram without charge-reservoir layers, potentially clarifying the interplay between antiferromagnetism and superconductivity at low doping.

major comments (3)
  1. [Abstract] Abstract: the assertion that AF folding 'emerges from Fermi arcs within the film's single Fermi surface' at p~0.07 (Luttinger volume) is internally inconsistent with the unreconstructed Luttinger count; folding implies possible band reconstruction, which would alter the enclosed area and invalidate the direct mapping area=(1+p) per Cu without additional justification.
  2. [Results] Results/ARPES analysis: no quantitative error bars, raw momentum-distribution curves, or Fermi-surface volume uncertainties are reported for the p~0.07 extraction, nor are cross-checks against transport Hall data or annealing-induced stoichiometry shifts provided; these omissions directly undermine the load-bearing claim that the observed Tc>60 K occurs at this specific doping.
  3. [Methods] Methods/Film characterization: surface sensitivity of ARPES on ~10 nm films is not addressed with controls for termination, Eu/Li segregation, or oxygen non-stoichiometry; without such controls the measured volume cannot be shown to reflect the bulk doping that sets the reported superconductivity.
minor comments (2)
  1. [Abstract] Abstract: the compound notation (Ca,Li)CuO2+δ should specify whether δ denotes excess oxygen or a different deviation.
  2. Figure captions (assumed from context): anisotropy data would benefit from explicit statement of measurement geometry relative to CuO2 planes.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We appreciate the referee's thorough review and valuable feedback on our manuscript. Below, we provide point-by-point responses to the major comments. We have revised the manuscript to address the concerns raised regarding the abstract claim, data quantification, and film characterization.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the assertion that AF folding 'emerges from Fermi arcs within the film's single Fermi surface' at p~0.07 (Luttinger volume) is internally inconsistent with the unreconstructed Luttinger count; folding implies possible band reconstruction, which would alter the enclosed area and invalidate the direct mapping area=(1+p) per Cu without additional justification.

    Authors: We thank the referee for highlighting this important point. The observed Fermi surface in our ARPES data appears as a single contour, from which the Luttinger volume is calculated to yield p ≈ 0.07. The antiferromagnetic folding is manifested as additional spectral weight or shadow features emerging from the Fermi arcs, indicating coexistence of AF order with the superconducting state rather than a complete reconstruction of the Fermi surface. To address the potential inconsistency, we have revised the abstract to better specify that the doping is determined from the primary unreconstructed Fermi surface contour, and we have added a detailed explanation in the main text justifying why the volume count remains valid at this doping level where the folding is partial. revision: yes

  2. Referee: [Results] Results/ARPES analysis: no quantitative error bars, raw momentum-distribution curves, or Fermi-surface volume uncertainties are reported for the p~0.07 extraction, nor are cross-checks against transport Hall data or annealing-induced stoichiometry shifts provided; these omissions directly undermine the load-bearing claim that the observed Tc>60 K occurs at this specific doping.

    Authors: We agree that providing quantitative uncertainties and raw data is essential for validating the doping level. In the revised manuscript, we have added error bars to the reported doping values based on the uncertainty in fitting the Fermi surface contours and Luttinger volume calculation. Raw momentum-distribution curves are now included in the supplementary materials. We have also incorporated a discussion of cross-checks with available transport data on similar films and analysis of annealing effects on stoichiometry, although comprehensive Hall measurements on these specific thin films were not performed due to experimental constraints. revision: yes

  3. Referee: [Methods] Methods/Film characterization: surface sensitivity of ARPES on ~10 nm films is not addressed with controls for termination, Eu/Li segregation, or oxygen non-stoichiometry; without such controls the measured volume cannot be shown to reflect the bulk doping that sets the reported superconductivity.

    Authors: The surface sensitivity of ARPES is a valid concern for thin-film samples. We have expanded the Methods section to include additional characterization data, such as XPS measurements to assess surface termination and composition, and we discuss the growth conditions that minimize Eu/Li segregation. Oxygen non-stoichiometry is controlled via post-annealing, with transport properties used as a proxy for bulk doping. While direct bulk-sensitive probes like resonant X-ray scattering were not applied in this study, the consistency between ARPES and transport measurements supports the correspondence. We acknowledge that more extensive controls could strengthen the claim and note this as a direction for future work. revision: partial

Circularity Check

0 steps flagged

No circularity: experimental observations rest on direct measurements and standard Luttinger count

full rationale

The paper reports synthesis of bipolar-doped infinite-layer films, ARPES Fermi-surface maps, and transport data. Hole doping is extracted via the established 2D Luttinger theorem applied to measured Fermi-surface areas (area = (1 + p) per Cu), an external theorem independent of the Tc or band-folding results. No equations, fitted parameters, or self-citations reduce the reported Tc > 60 K, AF folding, or phase diagram to the input data by construction. The central claims are falsifiable by independent bulk probes or different surface terminations and do not rely on any of the enumerated circular patterns.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard assumptions of ARPES analysis and thin-film growth rather than new postulates; the main free parameter is the doping level extracted from data.

free parameters (1)
  • hole doping level = ~0.07
    Extracted via Luttinger volume from ARPES Fermi surface area; central claim uses the value ~0.07
axioms (2)
  • domain assumption Luttinger theorem holds for the Fermi surface volume in these doped infinite-layer cuprates
    Invoked to convert measured Fermi surface area into carrier density
  • domain assumption The observed resistance anisotropy and band folding originate from the bulk CuO2 planes rather than surface or interface states
    Implicit in interpreting transport and ARPES data as intrinsic to the infinite-layer structure

pith-pipeline@v0.9.1-grok · 5760 in / 1527 out tokens · 17905 ms · 2026-06-28T07:54:06.716588+00:00 · methodology

discussion (0)

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Reference graph

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