Daily Overview: Today’s highlights focus on an in-depth understanding of the electronic structure and magnetic order of mixed Ruddlesden-Popper nickelates, revealing a new pathway to achieving bulk superconductivity. In [1], theoretical studies show that hole doping of the bilayer nickelate La₃Ni₂O₇ under ambient pressure induces nearly perfect Fermi surface nesting, significantly enhancing antiferromagnetic spin fluctuations and raising the superconducting transition temperature to experimentally observable levels, providing a feasible route to bulk superconductivity without the need for high pressure or strain. In [2], spin-polarized scanning tunneling microscopy was used to image the stripe order in the trilayer nickelate La₄Ni₃O₁₀ in real space, revealing that its periodicity and gap characteristics are highly similar to those of cuprate high-temperature superconductors. For the first time, atomic-scale stripe dynamics triggered by tunneling electrons were observed, offering key clues for understanding the pairing mechanism in nickel-based superconductors. In [3], a unified itinerant description framework was developed for the magnetic nature of spin density wave order in RP nickelates, indicating that the magnetism in La₃Ni₂O₇ and La₄Ni₃O₁₀ arises from mirror-selective interband scattering rather than local magnetic moments, thereby revising the traditional understanding of effective exchange interactions. arXiv submission processing window: 2026-05-20 00:00 to 2026-05-20 00:00 UTC.

1. Nearly perfect Fermi surface nesting in hole-doped La$_3$Ni$_2$O$_7$ enables bulk superconductivity without pressure or strain

Summary: This study solves the superconducting gap equation of the hole-doped bilayer nickelate La₃₋ₓSrₓNi₂O₇ under ambient pressure by combining density functional theory, dynamical mean-field theory, and random phase approximation. The results reveal that hole doping induces a Ni-d₃z²₋r² orbital-derived γ Fermi pocket, whose size and shape can be tuned by the doping level x; when x approaches 0.4, the γ pocket evolves from circular to diamond-shaped and expands to half the Brillouin zone, forming nearly perfect Fermi surface nesting (optimal nesting vector Q=(π,π)), which significantly enhances antiferromagnetic spin fluctuations and boosts the superconducting eigenvalue to an experimentally observable level. This work elucidates the mechanism and an experimentally feasible route to achieving bulk superconductivity in La₃Ni₂O₇ without the need for high pressure or strain.

2. Imaging stripe dynamics in trilayer nickelate La$_4$Ni$_3$O$_{10}$

Summary: This study employed spin-polarized scanning tunneling microscopy to perform real-space imaging of the stripe order in the trilayer nickelate La₄Ni₃O₁₀, revealing its local magnetic and charge distributions. The experiments showed that the stripe order exhibits a four-unit-cell periodicity, highly reminiscent of the stripe order in cuprate high-temperature superconductors, and opens a nearly complete energy gap of approximately 66 meV near the Fermi level. More importantly, when the tunneling electron energy exceeds a threshold of about 20 meV, discrete phase slips can be triggered, enabling atomic-scale imaging of stripe dynamics. These results underscore the crucial role of correlated physics in driving stripe-like order in lanthanum nickelates and reveal striking similarities to cuprate superconductors, providing important clues for understanding the pairing mechanism in nickel-based superconductors.

3. Itinerant Nature of Spin-Density-Wave Order in Ruddlesden-Popper Nickelates

Summary: This study develops a unified itinerant description framework to address the magnetic nature of spin density wave (SDW) order in Ruddlesden-Popper nickelates. Methodologically, by leveraging the multilayer mirror structure of NiO₂ blocks to partition low-energy electronic states into mirror-even and mirror-odd sectors, it is found that dominant interband scattering—specifically nesting between bands of opposite mirror parity—drives a mirror-selective itinerant SDW instability. Key findings: in La₃Ni₂O₇ and La₄Ni₃O₁₀, this framework not only accurately reproduces the experimentally observed SDW wave vectors and spin textures, but its collective excitation modes naturally yield spin-wave-like magnetic excitation spectra, with the small ordered moment arising from Fermi surface reconstruction rather than local moments. For La₄Ni₃O₁₀, the SDW further induces a secondary mirror-even charge density wave through intraband coherence, resulting in an intertwined spin and charge texture. The conclusion indicates that magnetism in multilayer nickelates is fundamentally itinerant rather than originating from local moments, so the large effective exchange couplings previously extracted from spin-wave fits do not correspond to microscopic superexchange interactions; instead, mirror-selective interband SDW order serves as a unifying organizing principle for understanding magnetic correlations in these systems.