Source capture
Authors Chihao Li, Yutong Chen, Yaolong Bian, Yihao Zhang, Jiahao Ye, Zhitong An, Xingtian Sun, Yu Fan, Zhihui Chen, Zhanze Wang, Jinglei Zhang, Haichao Xu, Rui Peng, Donglai Feng
arXiv / Publisher https://arxiv.org/abs/2607.16684
PDF https://arxiv.org/pdf/2607.16684
Relevance score 5.351
Primary category cond-mat.supr-con
Published 2026-07-21
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Summary

This study finds that zero resistance and a diamagnetic response are observed in stoichiometric PrNiO2 thin films without cation substitution and in the absence of a capping layer, thereby confirming the intrinsic superconductivity of the parent infinite-layer nickelate. Heterostructure engineering by inserting a non-superconducting buffer layer rules out contributions from substrate interface effects. Isovalent trivalent La substitution likewise preserves superconductivity, demonstrating that the phenomenon is not unique to PrNiO2. In contrast, trace divalent Sr or Ca substitution (within about 3%) rapidly suppresses superconductivity so that it no longer appears. Combined with angle-resolved photoemission spectroscopy measurements, this reveals that the superconducting phase is confined to an extremely narrow hole-doping range within 3% beyond the parent PrNiO2. A non-superconducting region exists between this phase and the previously established superconducting dome at approximately 20% divalent doping, giving rise to two separated superconducting regions on the phase diagram. Furthermore, the parent superconducting phase exhibits a significantly stronger upper critical field anisotropy. These results indicate that infinite-layer nickelates are not simply cuprate analogs but possess unique superconducting physics and segregated superconducting domains.

Materials

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Methods

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Keywords

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Highlights

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Conclusions

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Main claims

  • Pristine stoichiometric PrNiO2 exhibits intrinsic superconductivity with zero resistance and diamagnetism.
    • Evidence: Figure 1b shows zero resistance below ≈7 K.,Figure 1f shows diamagnetic frequency shift in TDO.
  • Superconductivity is not an interfacial effect from the SrTiO3 substrate.
    • Evidence: Figure 1h: heterostructure with non-superconducting Ca-doped spacer retains robust zero-resistance transition.
  • The superconducting phase is confined to within 3% additional hole doping from the parent state.
    • Evidence: Figure 2e,f: superconductivity suppressed by 3% Sr or Ca substitution, insulating behavior for Ca.
  • This new superconducting regime is disconnected from the previously established hole-doped dome.
    • Evidence: Figure 4a phase diagram shows a non-superconducting gap between the near-parent regime and the dome at ≈20% doping.
  • The parent superconducting regime exhibits enhanced upper-critical-field anisotropy compared to the hole-doped dome.
    • Evidence: Figure 4b: in-plane Hc2 far exceeds Pauli limit and anisotropy γ ≈68 near Tc, stronger than reported for optimally doped nickelates.

Workflow

  • sample_synthesis — High-quality stoichiometric PrNiO2 films are essential for observing intrinsic superconductivity.
    • Materials: PrNiO2; SrTiO3 substrate
    • Methods: pulsed laser deposition (inferred); stoichiometry tuning (Pr/Ni ratio)
    • Observations: low normal-state resistivity below quantum of resistance; suppressed low-temperature resistivity upturn
  • transport_characterization — Uncapped PrNiO2 shows reproducible zero-resistance superconductivity.
    • Materials: PrNiO2 films; magnetic field system up to 9T
    • Methods: four-probe resistivity vs. temperature; magnetic field sweeps in-plane and out-of-plane
    • Observations: zero resistance below ≈7K; superconducting transition progressively suppressed by magnetic field
  • diamagnetic_measurement — Diamagnetic response confirms bulk superconductivity with both hallmarks (zero resistance and Meissner effect).
    • Materials: PrNiO2 film; tunnel diode oscillator (TDO) circuit
    • Methods: TDO frequency shift detection
    • Observations: clear frequency shift indicating diamagnetic shielding
  • interface_exclusion — Superconductivity is intrinsic to PrNiO2, not driven by substrate interface effects.
    • Materials: PrNiO2; Pr0.97Ca0.03NiO2; SrTiO3
    • Methods: insertion of 3-uc non-superconducting Ca-doped spacer layer
    • Observations: robust zero-resistance transition persists with comparable Tc
  • doping_dependence — Superconducting phase exists only within 3% hole doping from parent state, distinct from higher-doped dome.
    • Materials: LaxPr1-xNiO2 films; Pr1-xSrxNiO2 films; Pr1-xCaxNiO2 films
    • Methods: transport measurements with substitution
    • Observations: superconductivity preserved under La; rapid suppression by Sr or Ca at 3%, insulating behavior for Ca; no superconductivity for x ≥ 0.03
  • electronic_structure — Superconducting parent PrNiO2 is self-doped with ≈9% holes; Ca doping adds holes without significant disorder.
    • Materials: PrNiO2 and Pr0.95Ca0.05NiO2 films
    • Methods: angle-resolved photoemission spectroscopy (ARPES); Hall effect measurements
    • Observations: hole-like α pocket and electron-like β pocket at EF; hole doping ≈9% in Ni 3dx2-y2 from Luttinger volume; negligible MDC broadening upon Ca substitution; negative Hall coefficient in PrNiO2
  • phase_diagram_analysis — Infinite-layer nickelates host two disconnected superconducting regimes with distinct critical field anisotropy.
    • Materials: resistivity vs. doping data; high-field transport up to 35T
    • Methods: construction of hole-doping phase diagram; extraction of upper critical field Hc2 and anisotropy
    • Observations: two disjoint superconducting regions separated by non-superconducting gap; in-plane Hc2 exceeds Pauli limit, out-of-plane Hc2 shows upturn; anisotropy γ = Hc2[ab]/Hc2[c] ≈68 near Tc