Daily Overview: Today’s highlights focus on the in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], Zhou et al. achieved a superconducting onset temperature of approximately 63 K in (La,Pr)₃Ni₂O₂ thin films under ambient pressure via giant oxidative atomic layer epitaxy, and found that the superconducting enhancement is closely associated with strange metal behavior (α≈1), with significantly stronger interlayer coupling than that of bismuth-based cuprates. In [2], Wang et al.’s high-field transport study of La₂.₈₂Sr₀.₁₈Ni₂O₇ thin films revealed that the in-plane upper critical field is strongly suppressed by the Pauli paramagnetic limit (approximately 58 T), with an anisotropy ratio γ≈1.34, supporting a three-dimensional bulk superconductivity in this system and highlighting the critical role of spin paramagnetic effects in determining the high-field phase diagram. In [3], Sanchez-Manzano et al. characterized the superconducting dimensionality of infinite-layer Pr₀.₈Sr₀.₂NiO₂ thin films through vortex phase diagrams, discovering a quasi-two-dimensional vortex liquid-to-glass transition at low disorder, while enhanced disorder drives the system into a purely two-dimensional state, establishing disorder strength as a key tuning parameter. These three works collectively reveal the intrinsic relationships among dimensionality, interlayer coupling, and anomalous normal-state behavior in nickel-based superconductivity from the perspectives of superconducting enhancement mechanisms, paramagnetic pair-breaking limits, and vortex dimensionality tuning. arXiv submission processing window: 2026-03-12 00:00 to 2026-03-12 00:00 UTC.

1. Superconductivity onset above 60 K in ambient-pressure nickelate films

Summary: This study employed the enormous oxidation atomic layer epitaxy method to grow (La,Pr)3Ni2O7 thin films on SrLaAlO4 substrates under extreme non-equilibrium conditions, achieving a superconducting onset transition temperature of approximately 63 K at ambient pressure, with zero-resistance temperature reaching about 37 K and diamagnetic signal onset at around 23 K. This method overcomes the structural instability of the metastable superconducting phase through high-temperature and in-situ sufficient oxidation; X-ray diffraction and scanning transmission electron microscopy confirmed that the films possess large-scale crystalline purity. Transport measurements reveal a systematic evolution of the normal-state resistivity temperature power-law exponent α from Fermi liquid behavior (α≈2) in samples with low onset transition temperatures to strange metal behavior (α≈1) in samples with high onset transition temperatures, directly correlating enhanced superconductivity with non-Fermi liquid behavior. The vortex melting phase diagram constructed via mutual inductance technique indicates that the two-dimensional melting limit is suppressed to near zero, with interlayer coupling strength significantly stronger than that of bismuth-based cuprates. These results demonstrate that nickelates are strange metal high-temperature superconductors with strong interlayer coupling at ambient pressure.

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

Summary: This study employs epitaxial La2.82Sr0.18Ni2O7 thin films (with a superconducting transition temperature of approximately 31.6 K) to systematically characterize the upper critical field and its anisotropy via high-field transport measurements up to 58 T. Near the transition temperature, superconductivity exhibits thickness-limited two-dimensional characteristics; upon cooling, the out-of-plane coherence length decreases to below the film thickness (6 nm), indicating a transition to intrinsic three-dimensional bulk superconductivity. Based on the Ginzburg-Landau model, the zero-temperature in-plane and out-of-plane upper critical fields are determined to be 82 T and 45 T, respectively, yielding an anisotropy ratio γ≈1.34, comparable to that of bulk Ruddlesden-Popper nickelates. At low temperatures, the in-plane upper critical field is strongly suppressed by the spin paramagnetic pair-breaking effect, approaching the Pauli limit (58 T), while the out-of-plane direction remains largely unaffected. This anisotropic Pauli limiting explains the reduced anisotropy of the upper critical field and supports the conclusion that superconductivity in the films is inherently three-dimensional bulk superconductivity. The results highlight the critical role of spin paramagnetic effects in determining the high-field superconducting phase diagram of these nickelates.

3. Dimensionality of vortex matter in superconducting infinite-layer nickelates

Summary: This study investigates the dimensionality of the superconducting state in infinite-layer nickel oxides by mapping the vortex phase diagram of superconducting Pr0.8Sr0.2NiO2 thin films from multiple perspectives. Experimental results reveal that low-disorder films exhibit a quasi-two-dimensional vortex liquid-to-glass transition, while increasing disorder drives the system into a pure two-dimensional state. This finding indicates that pure two-dimensionality is not an intrinsic property but an extrinsic phenomenon caused by the decoupling of NiO2 layers due to enhanced disorder. The work establishes disorder as a key tuning parameter for superconductivity in infinite-layer nickel oxides and identifies that disorder primarily resides within the NiO2 layers, offering two fundamental insights for understanding this class of materials.