Source capture
Authors Zhiwei Wang, Zhengjie Wang, Huiyu Wang, Mingyi Zhu, Mengzu Shi, Zongyao Huang, Houpu Li, Shoucong Ning, Jing Tao, Tao Wu, Xianhui Chen
arXiv / Publisher https://arxiv.org/abs/2608.01295
PDF https://arxiv.org/pdf/2608.01295
Relevance score 5.927
Primary category cond-mat.supr-con
Published 2026-08-04
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Summary

Using ozone-assisted atomic layer epitaxy, the researchers grew La2PrNi2O7 thin films on NdAlO3 substrates, introducing an extreme compressive strain of up to −2.14% and achieving high-temperature superconductivity with an onset critical temperature of 60 K, a zero-resistance temperature of 33 K, and a diamagnetic transition at 20 K, while magnetotransport measurements confirmed a quasi-two-dimensional superconducting state. A comparison of the phase diagrams between the strained films and high-pressure bulk materials reveals that, although both suppress spin-density waves to drive superconductivity, the lattice responses diverge: the film’s c-axis parameter window markedly departs, whereas the in-plane parameters coincide with those of the bulk. Crucially, Hall measurements uncover a dichotomy in electronic character, as the optimal superconducting film exhibits a negative Hall coefficient indicative of electron-like behavior, in stark contrast to the positive, hole-like Hall coefficient of high-pressure bulk samples and non-superconducting tensile-strained films. These observations indicate that both strain and pressure strategies effectively tune the underlying correlation modulation beyond the constraints of a specific Fermi surface topology, thereby enabling superconductivity. This work establishes a macroscopic platform for studying multi-orbital physics in nickelates and provides a new dimension for exploring the mechanism of high-temperature superconductivity.

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

  • Via ozone-assisted atomic-layer epitaxy, we realized high-temperature superconductivity in as-grown La2PrNi2O7 films on NdAlO3 substrates under extreme compressive strain (-2.14%).
    • Evidence: Abstract: these films exhibit a Tc_onset of 60 K, zero resistance at 33 K, and a diamagnetic response at 20K
  • Superconductivity in these films is quasi-two-dimensional.
    • Evidence: Abstract: magnetotransport measurements confirming a quasi-two-dimensional superconducting nature,Fig. 3d and Tinkham model fitting
  • Optimal superconducting films are intrinsically electron-like (negative Hall coefficient), in stark contrast to the hole-like nature of high-pressure bulk crystals.
    • Evidence: Abstract: Hall measurements reveal a fundamental electronic dichotomy: optimal superconducting films are intrinsically electron-like (exhibiting a negative Hall coefficient),Fig. 3e shows negative R_H for NAO film
  • Both compressive strain and pressure tune the underlying correlation landscape, transcending specific Fermi surface topologies.
    • Evidence: Abstract: both tuning strategies effectively modulate the underlying correlation landscape - the true driver of superconductivity - transcending the constraints of specific Fermi surface topologies
  • Superconductivity emerges from the suppression of spin-density waves (SDW).
    • Evidence: Abstract: while superconductivity in both systems emerges from the suppression of spin-density waves (SDW),Discussion references microscopic insights linking strain/pressure to SDW suppression

Workflow

  • sample_preparation — High-qualityLa2PrNi2O7 films with controlled stoichiometry and extreme compressive strain up to -2.14% were synthesized.
    • Materials: La2PrNi2O7 targets; NdAlO3, SrLaAlO4, LaAlO3, (La,Sr)(Al,Ta)O3 substrates; ozone; oxygen
    • Methods: ozone-assisted atomic-layer-by-layer epitaxy; RHEED monitoring; dynamic atomic rearrangement after each layer
    • Observations: RHEED oscillations indicating layer-by-layer growth; phase-pure 3-unit-cell thick films; coherently strained to substrates
  • measurement — Superconductivity with quasi-2D character is established, and carrier sign varies systematically with strain.
    • Materials: film samples on substrates
    • Methods: resistivity measurements in PPMS; Hall bar geometry; magnetotransport up to 9T; mutual inductance technique; XRD 2θ-ω scans; reciprocal space mapping; HAADF-STEM imaging; EDS elemental mapping
    • Observations: Tc,onset = 60 K, Tc,zero = 33K; diamagnetic transition at 20K; negative Hall coefficient for NAO and SLAO films, positive for LAO and LSAT; linear field dependence of Hall resistivity; upper critical field anisotropy; c-axis lattice constant 20.86 Å
  • analysis — Quantitative analysis confirms 2D superconductivity and reveals strain-dependent scattering mechanisms.
    • Materials: experimental data from transport and structure
    • Methods: Ginzburg-Landau extrapolation for upper critical fields; 2D Tinkham model fitting for angular Tc; Mott-Ioffe-Regel saturation model for resistivity; Nelson-Riley fit for lattice constants; extraction of Hall coefficient
    • Observations: ξab(0) ≈ 1.98 nm, effective thickness d ≈ 4 nm; coherence length close to physical thickness; anisotropy γ ≈ 1.71; Tinkham model matches angular data; n exponent decreases from 2.6 to 1.4 with strain
  • interpretation — Biaxial compressive strain alone, decoupled from interfacial doping, drives superconductivity by suppressing SDW and modulating electronic correlations, yielding electron-like carriers distinct from hole-like bulk, while lattice response diverges in the c-axis.