摘要
研究人员利用臭氧辅助原子层外延技术，在NdAlO3衬底上生长了La2PrNi2O7薄膜，引入了高达-2.14%的极端压缩应变，实现了起始临界温度达60 K、零电阻温度33 K和20 K处抗磁转变的高温超导性，磁输运测量确认其为准二维超导态。对比应变片与高压块材的相图发现，尽管两者都通过抑制自旋密度波驱动超导，但晶格响应存在分歧：薄膜在其c轴参数窗口显著发散，而面内参数与块材一致。关键的是，霍尔测量揭示了电子性质的二分性，最佳超导薄膜呈现负霍尔系数的类电子特征，与高压块材和非超导拉伸正系数的类空穴特征截然对立。这表明应变与压力策略均能有效调控潜在关联调制，超越特定费米面拓扑的限制，从而驱动超导性。这项工作建立了一个研究镍酸盐多轨道物理的宏观平台，为探索高温超导机制提供了新维度。
材料
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方法
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关键词
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亮点
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结论
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主要论断
- 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%).
- 证据: 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.
- 证据: 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.
- 证据: 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.
- 证据: 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).
- 证据: 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
研究流程
- sample_preparation — High-qualityLa2PrNi2O7 films with controlled stoichiometry and extreme compressive strain up to -2.14% were synthesized.
- 材料: La2PrNi2O7 targets; NdAlO3, SrLaAlO4, LaAlO3, (La,Sr)(Al,Ta)O3 substrates; ozone; oxygen
- 方法: ozone-assisted atomic-layer-by-layer epitaxy; RHEED monitoring; dynamic atomic rearrangement after each layer
- 观察: 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.
- 材料: film samples on substrates
- 方法: 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
- 观察: 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.
- 材料: experimental data from transport and structure
- 方法: 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
- 观察: 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.