[论文解读] Pauli-limited upper critical field and anisotropic depairing effect of La2.82Sr0.18Ni2O7 superconducting thin film

Ke Wang, Maosen Wang+11 more|arXiv (Cornell University)|Mar 11, 2026

Physics of Superconductivity and Magnetism被引用 0

一句话总结

该研究在La2.82Sr0.18Ni2O7薄膜中报道了带各向异性解对的Pauli极限上临界场，显示出厚度驱动的维度跨越以及平面内–法线方向Hc2各向异性的适度存在。

ABSTRACT

We investigate the upper critical field and superconducting anisotropy of epitaxial La2.82Sr0.18Ni2O7 thin films, which show a sharp superconducting transition at Tc=31.6 K. Near Tc, superconductivity exhibits thickness-limited two-dimensional characteristics. Upon cooling, the out-of-plane coherence length decreases below the sample thickness of 6 nm, corresponding to a 3-unit-cell film, indicating a crossover to intrinsic three-dimensional bulk superconductivity. High-field transport measurements reveal large upper critical fields with a small anisotropy ratio gama~1.34, comparable to bulk Ruddlesden-Popper nickelates. At low temperatures, the in-plane (ab) upper critical field Hc2(ab) is strongly suppressed by spin-paramagnetic pair breaking and approaches the Pauli limit (Hc2(Pauli)=58 T), while Hc2(c) remains largely unaffected. This anisotropic Pauli limitation accounts for the reduced upper critical field anisotropy and supports the conclusion that superconductivity in these films is fundamentally three-dimensional bulk like. Our results highlight the essential role of spin-paramagnetic effects in shaping the high-field superconducting phase diagram of Ruddlesden-Popper nickelates.

研究动机与目标

• 研究La2.82Sr0.18Ni2O7薄膜的上临界场与超导各向异性。
• 通过厚度表征从2D样向3D体积样超导性的维度跨越。
• 评估在Ruddlesden-Popper型镍氧化物高场超导中自旋参数性成对破坏的作用。

提出的方法

• 对外延生长的La2.82Sr0.18Ni2O7薄膜进行高场传输测量。
• 分析厚度效应，指示Tc附近的2D量纲，及Tc以下向3D体积样行为的跨越。
• 提取平行(ab)和垂直(c)方向的Hc2，并评估自旋参数性极限。
• 与Pauli极限比较并从Hc2(ab)与Hc2(c)评估各向异性γ。

实验结果

研究问题

• RQ1 La2.82Sr0.18Ni2O7薄膜在ab和c方向上的上临界场Hc2是多少？
• RQ2 自旋参数性成对破坏在Hc2上，特别是Hc2(ab)上有多大影响？
• RQ3 是否存在厚度驱动的维度跨越，指示从2D到3D超导性的转变？
• RQ4 各向异性比值γ是多少，与块状镍氧化物相比有何差异？

主要发现

• Hc2(ab)受到自旋参数性成对破坏的强烈抑制，接近Pauli极限(Hc2(Pauli)=58 T)。
• Hc2(c)在很大程度上不受自旋参数性效应影响。
• 测得的各向异性γ约为1.34，表明上临界场各向异性减小。
• 厚度约为6 nm（3单元胞薄膜）标志着向固有三维体积样超导性的跨越。
• 总体结果支持具有重要自旋参数性形成的高场相图的三维体积样超导态。