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This study proposes that incoherent electronic states in strongly correlated materials arise not from disorder or material-specific mechanisms, but from self-generated dynamical disorder induced by competing fluctuations. In this marginal dynamical regime, electron dynamics naturally couple with time-dependent scattering, yielding the spectral function form ρ(z)=exp(-z²/4)D_ν(z), where z is the scaled energy, D_ν is the parabolic cylinder function, and ν=-1/2 is fixed. By independently scaling the angle-resolved photoemission spectroscopy (ARPES) energy distribution curves of the cuprates Nd₂₋ₓCeₓCuO₄ and Bi₂Sr₂CaCu₂O₈₊δ, the Kagome metal CsCr₃Sb₅, and the bilayer nickelate La₃Ni₂O₇, all datasets collapse onto a single universal curve, with only the amplitude and energy scale varying among materials. This spectral collapse indicates that microscopic details such as lattice geometry, band structure, and chemical composition become irrelevant in the low-energy regime, exhibiting fixed-point-like dynamical behavior. The result establishes a unified quantitative framework for the continuously dominant ARPES spectra across diverse strongly correlated materials.

The recent discovery of high-temperature superconductivity in bilayer nickelate La3Ni2O7−δ single crystals under high pressure has sparked significant interest in the correlated electronic physics and unconventional pairing mechanisms within Ruddlesden-Popper phase nickelates, where the oxygen content plays a crucial role in both structure and superconductivity. Here we report the evolution of the structure and density wave order in La3Ni2O7−δ single crystals at ambient pressure under various oxygen annealing conditions. Structural analysis reveals that with the increase of annealing oxygen pressure, La3Ni2O7−δ undergoes a structural phase transition from an orthorhombic to a tetragonal phase. Magnetic torque measurements indicate that the density wave order, present in the orthorhombic phase, vanishes upon transition to the tetragonal structure, accompanied by an abrupt change in carrier concentration. A phase diagram illustrating the dependence of both the crystal structure and density wave order on the annealing oxygen pressure is mapped. Our findings suggest a promising pathway for studying the interplay between structure, density wave order, and superconductivity in bulk nickel-based materials.

This paper systematically measures the superfluid density of the infinite-layer nickel-based superconductor Nd1-xSrxNiO2 within the doping superconducting dome using the mutual inductance method. The results show that the superfluid stiffness is weak and exhibits an approximate square-root relationship with the superconducting transition temperature Tc. Additionally, a strong interaction between the Nd 4f magnetic moments and the superfluid is observed, leading to a significant suppression of the superfluid density at low temperatures, with an effect far beyond simple paramagnetic explanations, suggesting a coupling between magnetic order and the superconducting phase. These findings indicate that superconducting phase fluctuations play an important role in limiting Tc and reveal an unexpectedly strong coupling between rare-earth magnetic ions and the superfluid.

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Oxygen-deficient nickelate thin films were fabricated on highly reduced and conductive SrTiO₃ substrates, and through Meissner effect and transport measurements, a superconducting onset temperature of 50–70 K was observed, with zero resistance achieved at 20–25 K, indicating the presence of superconductivity in island-like regions within the film. A giant paramagnetic Meissner effect peak appeared at approximately 48 K, further supporting the occurrence of a superconducting transition near this temperature. Additionally, a non-reciprocal, hysteresis-free superconducting diode effect was observed, with its polarity fully polarizable and reversible. The thin films comprise a mixture of various Ruddlesden–Popper phases, including the infinite-layer phase. These enhanced superconducting properties are attributed to the synergistic effect between the oxygen-deficient films and the highly reduced SrTiO₃ substrates.

Bilayer Ruddlesden-Popper nickelates exhibit superconductivity near 80 K under high pressure, and recent work has stabilized RA₃Ni₂O₇ (RA = rare earth or alkaline earth element) superconducting thin films at ambient pressure via epitaxial strain, enabling transport, spectroscopic, microscopic, and device measurements. This review summarizes experimental progress on ambient-pressure superconducting bilayer nickelate thin films, covering synthesis routes, oxygen stoichiometry, substrate-induced strain, normal-state transport, superconducting properties, doping phase diagrams, and momentum-resolved electronic structure. Key unresolved issues include the reproducibility of phase-pure ultrathin films, the microscopic origin of the two-step superconducting transition, the roles of oxygen defects and substrate doping, the position of the Ni 3dz₂-derived γ band, and the pairing symmetry. The review concludes that future work must establish more quantitative links between crystal structure, orbital reconstruction, and superconductivity to deepen the understanding of this unconventional high-temperature superconducting system.

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