Daily Overview: Today’s highlighted studies focus on the relationship between pressure, lattice, superconductivity, and magnetic order in bilayer Ruddlesden-Popper nickelates. A hydrostatic-pressure electronic Raman scattering study of La₃Ni₂O₇ single crystals shows that, with increasing pressure, the spin-density-wave (SDW) gap and transition temperature generally increase, while the dimensionless coupling ratio remains stable at about 7.5, indicating that the SDW state has strong-coupling character; however, the broadening of the SDW peak indicates that its long-range coherence is weakened, providing spectroscopic constraints for understanding the magnetic correlations associated with high-temperature superconductivity in bilayer nickelates. Another study of compressively strained La₂LnNi₂O₇ thin films finds that the superconducting transition temperature is approximately 41–42 K at ambient pressure and can be increased to 67–73 K under a high pressure of 16 GPa, whereas lattice compression induced by lanthanide substitution instead lowers Tc. Moreover, the variation of Tc correlates with the evolution of normal-state transport between T² and T-linear behavior, revealing the important influence of lattice structural changes on superconductivity in bilayer nickelates. arXiv submission processing window: 2026-08-19 00:00 to 2026-08-19 00:00 UTC.

1. Unconventional Pressure Evolution of Spin-Density-Wave State in La$_{3}$Ni$_{2}$O$_{7}$

Summary: We performed systematic electronic Raman scattering studies on single crystals of the bilayer nickelate La₃Ni₂O₇ under hydrostatic pressures up to 16.51 GPa, tracing the evolution of the spin-density-wave (SDW) state with pressure. The results show that both the SDW gap energy and the SDW transition temperature generally increase with increasing pressure, while the dimensionless coupling ratio 2Δ_SDW/(k_B T_SDW) remains approximately 7.5, indicating robust strong-coupling character of the SDW state. Concurrently, the SDW Raman peak progressively broadens with pressure, suggesting that the long-range SDW ordering coherence gradually weakens. This work reveals an unusual pressure evolution in which the SDW energy scale is enhanced while the SDW state becomes increasingly incoherent, thereby providing spectroscopic constraints on magnetic correlations relevant to high-temperature superconductivity in bilayer nickelates.

2. Bridging ambient- and high-pressure superconductivity in La$_2$LnNi$_2$O$_7$ films

Summary: This study systematically investigates the superconductivity of compressively strained La₂LnNi₂O₇ thin films (Ln = lanthanide) under ambient and high pressure to clarify the relationship between ambient-pressure and high-pressure superconducting mechanisms. By suppressing the superconducting state with a 59 T magnetic field, the normal-state resistivity at ambient pressure tends toward T² behavior; after applying high pressure in a cubic anvil chamber, Tc increases from 41–42 K at ambient pressure to 67–73 K at 16 GPa. However, lattice compression induced by Ln substitution, although it may mimic pressure effects, lowers Tc. In both cases, Tc correlates with the evolution of normal-state transport between T² and T-linear behavior, indicating that lattice structural changes in bilayer nickelates have an important influence on superconductivity and providing clues for understanding the intrinsic connection between ambient-pressure strained films and high-pressure bulk superconducting states.