Evidence for structural and electronic rare-region physics in the nickelate La_2-xSr_xNiO₄

Recent x-ray and neutron scattering measurements of the cuprate La_2-xSr_xCuO₄ revealed an unusual exponential scaling with temperature of short-range orthorhombic correlations in the high-temperature tetragonal phase [1,2]. This scaling closely resembles the previously reported superconducting fluctuation behavior in cuprates and other oxide superconductors [3]. These observations indicate the prevalence of rare-region physics, where intrinsic inhomogeneity plays a crucial role in both the structural and electronic properties. Here we report similar behavior for La_2-xSr_xNiO₄, a non-superconducting isostructural analogue of La_2-xSr_xCuO₄, across a wide range of doping levels. Furthermore, we extend our investigation to spin and charge fluctuations of La_2-xSr_xNiO₄, which reveal similar characteristics. These findings highlight the significance of rare-region effects in perovskites and related oxides.

[1] D. Pelc et al., Sci. Rep. 12, 20483 (2022)

[2] R. J. Spieker et al., arXiv:2502.02947 (2025)

[3] D. Pelc et al., Nat. Commun. 10, 2729 (2019)