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arXiv · 2603.10717

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

Ke Wang·Maosen Wang·Wei Wei·Bo Hao·Mengqin Liu·Qiaochao Xiang·Xin Zhou·Qiang Hou·Yue Sun·Zengwei Zhu·Sheng Li·Yuefeng Nie·Zhixiang Shi
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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.

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Ke Wang, Maosen Wang, Wei Wei, Bo Hao, Mengqin Liu, Qiaochao Xiang, Xin Zhou, Qiang Hou, Yue Sun, Zengwei Zhu, Sheng Li, Yuefeng Nie, Zhixiang Shi. 2026-03-11. Pauli-limited upper critical field and anisotropic depairing effect of La2.82Sr0.18Ni2O7 superconducting thin film. https://doi.org/10.1016/j.mattod.2026.103269

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