Daily Overview: The highlights of today’s work focus on the in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. A review systematically summarizes the discovery, synthesis methods, and electronic properties of superconductivity in bilayer La₃Ni₂O₇ and trilayer La₄Ni₃O₁₀, emphasizing the importance of developing ambient-pressure superconducting phases. Another magnetotransport study observes the coexistence of linear-in-H magnetoresistance and T² resistivity in the normal state of overdoped infinite-layer La₁₋ₓSrₓNiO₂, providing key constraints for understanding the normal-state transport properties of this system. Meanwhile, theoretical work reveals, through multi-orbital cluster calculations, the redistribution of oxygen hole states in La₄Ni₃O₁₀ under pressure, identifying a transition in the hole localization mode between the central and outer layers, and elucidating similarities with the bilayer system in terms of spin-ordered states. These results collectively advance the understanding of the electronic structure, pairing mechanisms, and pressure effects in nickel-based superconductors. arXiv submission processing window: 2026-03-19 00:00 to 2026-03-19 00:00 UTC.

1. Superconducting Lanthanum Nickel Oxides with Bilayered and Trilayered Crystal Structures

Summary: In 2023, the bilayer nickel oxide La₃Ni₂O₇ was discovered to exhibit superconductivity at a pressure of approximately 14 GPa with a critical temperature near 80 K, featuring a structure similar to that of high-temperature copper oxides; subsequently, superconductivity was also found in the trilayer compound La₄Ni₃O₁₀. These two compounds belong to the Ruddlesden–Popper phase, which consists of alternating stacks of NiO₂ square-lattice layers and LaO rock-salt layers. Current research is mainly pursued along three directions: expanding the chemical diversity of the compounds, raising the superconducting transition temperature through elemental substitution, and elucidating the pairing mechanism of superconductivity. However, key experiments must be conducted under high pressure, which poses difficulties for mechanistic studies; therefore, developing nickel oxides that exhibit superconductivity at lower pressures or even ambient pressure is of great significance. This review summarizes the existing knowledge of these systems, highlights the relatively mature methods for sample synthesis and characterization, and briefly outlines their electronic properties, aiming to provide a foundation for future material exploration and physical understanding of the underlying mechanisms.

2. ${H}$-linear magnetoresistance in the ${T^2}$ resistivity regime of overdoped infinite-layer nickelate La$_{1-x}$Sr$_{x}$NiO$_2$

Summary: We report systematic magnetotransport measurements on high-crystallinity overdoped infinite-layer nickelate La₁₋ₓSrₓNiO₂ thin films (x = 0.20–0.24), revealing two prominent normal-state features in pulsed magnetic fields up to 62 T: the magnetoresistance violates Kohler’s rule and exhibits H-linear behavior at high H/T limits, while the normal-state resistivity consistently follows a T² dependence below 30 K. These results demonstrate the coexistence of H-linear magnetoresistance and T² resistivity in this model unconventional superconductor, providing new insights into the transport properties of the normal ground state that hosts superconductivity in infinite-layer nickelates.

3. Pressure induced redistribution of oxygen hole states in La$_{4}$Ni$_{3}$O$_{10}$

Summary: This paper employs density functional theory calculations combined with multi-orbital, multi-atomic cluster exact diagonalization including local exchange and Coulomb interactions to study the local low-energy electronic states of the trilayer nickel oxide La₄Ni₃O₁₀ using a minimal Ni₃O₁₄ cluster. The study finds that under ambient pressure, all three Ni ions are nominally +2 valent, with one of the two extra holes localized in the central NiO₂ layer, forming a Zhang-Rice singlet with the d_{x²-y²} orbital; the other hole predominantly occupies the antibonding combination of interlayer O p_z orbitals and hybridizes with an out-of-plane tri-spin polaron formed by the d_{z²} orbitals of the three NiO₂ layers. Consequently, the in-plane spin orientation is alternately carried by the outer d_{x²-y²} orbitals, with antiferromagnetic interlayer correlations, while the central layer is insulating with negligible magnetic moment. Under high pressure, the two extra holes concentrate on one outer layer and the inner layer, respectively, forming either a Zhang-Rice singlet or an in-plane tri-spin polaron on the d_{x²-y²} orbitals. The possible charge and spin ordered states suggested by the cluster results highlight the similarity between the bilayer La₃Ni₂O₇ and the trilayer La₄Ni₃O₁₀.