Interlayer electronic coherence links magnetism and superconductivity in Ruddlesden-Popper nickelates

摘要

本研究采用六端法对Ruddlesden-Popper镍酸盐双层与三层单晶进行高精度输运测量，自洽提取了面内与面外电阻率。结果发现，样品呈现强本征电子各向异性，面外电阻率表现出非单调温度依赖，揭示了普遍的层间相干至非相干渡越。在压力下，最大超导转变温度与环境压强下的电阻率各向异性成反比，表明更强的层间电子相干性有利于超导。此外，面外电阻率是磁性与密度波序的灵敏探针，而面内电阻率响应较弱。这些结果突出层间相干性作为关键调控参数，既追踪磁性关联，又与超导电性紧密相关，为镍基高温超导的微观理论提供了严格约束。

材料

• La₄Ni₃O₁₀
• Pr₄Ni₃O₁₀
• La₃Ni₂O₇

方法

• Si_x-terminal transport measurements
• High-precision dc transport
• Thermal expansion measurements

关键词

• interlayer electronic coherence
• resistivity anisotropy
• out of plane resistivity
• density wave order
• coherent to incoherent crossover
• fermi liquid behavior

亮点

• First self-consistent determination of intrinsic in-plane and out-of-plane resistivities in RP nickelates using the six-terminal method, minimizing artifacts.
• Establishes interlayer coherence as a key organizing parameter linking magnetism, dimensionality, and superconductivity in this family.

结论

• Strong intrinsic electronic anisotropy is observed in both bilayer and trilayer RP nickelates; out-of-plane resistivity exhibits nonmonotonic temperature dependence indicating a universal coherent-to-incoherent crossover in interlayer transport.
• The maximum superconducting T_c under pressure is inversely correlated with the ambient-pressure resistivity anisotropy, suggesting stronger interlayer coherence is favorable for superconductivity.
• Out-of-plane resistivity is an exceptionally sensitive probe of magnetic and density-wave orders, showing pronounced anomalies, while in-plane resistivity shows only weak signatures.

主要论断

• Strong intrinsic electronic anisotropy is revealed in bilayer and trilayer RP nickelates, with resistivity anisotropy γ_ρ reaching 10⁴ at low temperature in La₄Ni₃O₁₀, much larger than previously inferred from four-probe measurements.
  • 证据: Si_x-terminal geometry enables self-consistent extraction; large disparity between V_top and V_bot indicates strong current inhomogeneity; extracted γ_ρ values are 1.8×10⁴, 1.8×10³, and 1.7×10² for La₄Ni₃O₁₀, Pr₄Ni₃O₁₀, and La₃Ni₂O₇ respectively
• Out-of-plane resistivity exhibits a universal coherent-to-incoherent crossover with nonmonotonic temperature dependence, and is a sensitive probe of magnetic and density-wave orders.
  • 证据: ρ⊥ increases upon cooling through DW transitions, showing pronounced anomalies, while ρ∥ shows weak signatures; at low T, ρ⊥ recovers Fermi-liquid T² dependence
• The maximum superconducting T_c under pressure is inversely correlated with ambient-pressure resistivity anisotropy, indicating stronger interlayer electronic coherence favors superconductivity.
  • 证据: La₄Ni₃O₁₀ (highest anisotropy) has lowest T_c; La₃Ni₂O₇ (lowest anisotropy) has highest T_c; Pr₄Ni₃O₁₀ is intermediate

研究流程

• crystal_growth_and_preparation — High-quality single crystals of bilayer and trilayer RP nickelates.
  • 材料: La₄Ni₃O₁₀; Pr₄Ni₃O₁₀; La₃Ni₂O₇
  • 方法: high-pressure optical floating-zone growth; Laue orientation; mechanical polishing
  • 观察: high-quality single crystals with optically flat surfaces
• six_terminal_transport_measurements — Intrinsic transport anisotropy is much larger than previously reported.
  • 材料: gold contacts fabricated by sputtering
  • 方法: six-terminal geometry with contacts on top and bottom surfaces; self-consistent extraction of ρ∥ and ρ⊥
  • 观察: strong anisotropy: γ_ρ up to 10⁴ for La₄Ni₃O₁₀; nonmonotonic ρ⊥(T)
• thermal_expansion_measurements — Anisotropy enhancement is electronic in origin, not structural.
  • 材料: La₄Ni₃O₁₀ single crystal
  • 方法: capacitive dilatometry
  • 观察: out-of-plane lattice contraction through transition
• correlation_with_superconductivity — Stronger interlayer electronic coherence favors superconductivity.
  • 材料: literature T_c values under pressure
  • 方法: comparison of low-T anisotropy with max T_c
  • 观察: inverse correlation between anisotropy and T_c