Daily Overview: The highlighted work today focuses on the anisotropy of the superconducting state, low-energy vortex behavior, and competing density-wave order in Ruddlesden–Popper nickelates. In [1], the authors simultaneously measured the resistance and diamagnetism of (La,Pr)3Ni2O7 thin films and mapped the vortex melting phase diagram under in-plane and out-of-plane magnetic fields. They found that for H ∥ c, geometric confinement gives rise to pancake vortices, and that the anisotropy of the vortex melting field approaches 1 with decreasing temperature, indicating the formation of a nearly isotropic vortex solid and a nearly isotropic superfluid response. This is incompatible with a strictly two-dimensional Ni 3d_{x^2-y^2} band picture, but can be naturally explained by a substantial interlayer superfluid weight supplied by the Ni 3d_{z^2}-derived γ band, providing thermodynamic evidence that superconductivity in bilayer nickelates includes a contribution from the γ band. In [2], 139La NQR studies show that under pressure the spin-density wave and charge-density wave in La4Ni3O10 are intertwined: short-range density-wave order emerges at about 150 K and develops into long-range density-wave order at 139 K, while pressure suppresses the short-range and long-range orders at about 1 K/GPa and 10 K/GPa, respectively, indicating that the long-range order is suppressed more rapidly and competes with superconductivity. This result highlights that the coupling between density-wave order and unconventional superconductivity in trilayer nickelates differs from that in La3Ni2O7. From the perspectives of vortex thermodynamics and local spin/charge order, respectively, these two studies deepen the understanding of superconducting pairing and competing orders in nickelates. arXiv submission processing window: 2026-09-09 00:00 to 2026-09-09 00:00 UTC.

1. Nearly Isotropic Vortex Solid in $\mathbf{(La,Pr)_{3}Ni_{2}O_{7}}$ Thin Films

Summary: By simultaneously measuring the resistance and diamagnetism of (La,Pr)3Ni2O7 thin films and mapping the vortex-melting phase diagram under in-plane and out-of-plane magnetic fields, we investigated the anisotropy of superconductivity in bilayer nickelates. For H ∥ c, geometric confinement in ultrathin films leads to pancake vortices; the vortex-melting-field anisotropy parameter γ_Hm = H_m^ab/H_m^c decreases monotonically with decreasing temperature and approaches 1 at low temperatures, indicating the formation of a nearly isotropic vortex solid. Within anisotropic Ginzburg-Landau scaling, this ratio reflects the anisotropy of the superfluid density, and the results therefore point to a nearly isotropic superfluid response; this is incompatible with a contribution solely from the strictly two-dimensional Ni 3d_{x^2-y^2} band, but is naturally explained by a significant interlayer superfluid weight provided by the Ni 3d_{z^2}-derived γ band. This work provides thermodynamic evidence that superconductivity in bilayer nickelate thin films includes a substantial contribution from the γ band.

2. $^{139}$La nuclear quadrupole resonance studies of pressurized La$_4$Ni$_3$O$_{10}$

Summary: This study employs ¹³⁹La nuclear quadrupole resonance (NQR) spectroscopy to systematically investigate the density-wave order in single-crystalline La₄Ni₃O₁₀ under ambient pressure and 2.3 GPa hydrostatic pressure. The results show that the spin density wave and charge density wave in this material are intertwined, distinctly different from La₃Ni₂O₇; short-range density-wave order emerges around 150 K and develops into long-range density-wave order around 139 K. Upon applying pressure, the transition temperatures of the short-range and long-range density-wave orders decrease at rates of approximately 1 K/GPa and 10 K/GPa, respectively, indicating that the long-range order is suppressed more rapidly by pressure. On this basis, the authors propose that both the spin density wave and charge density wave in La₄Ni₃O₁₀ are competing orders of the superconducting state, providing new clues for understanding the interplay between density-wave order and unconventional superconductivity.