Evidence for rare-region physics in the structural and electronic degrees of freedom of the nickelate La$_{2-x}$Sr$_x$NiO$_4$

R. J. Spieker; B. Krohnke; D. Zhai; A. Lopez Benet; M. SpaiÄ; X. He; C. Y. Tan; Z. W. Anderson; F. Ye; H. Cao; M. J. Krogstad; R. Osborn; D. Pelc; M. Greven

paper

Evidence for rare-region physics in the structural and electronic degrees of freedom of the nickelate La $_{2 - x}$ Sr $_{x}$ NiO $_{4}$

arXiv:2512.23655

Abstract

We present a diffuse neutron and x-ray scattering study of structural, spin- and charge-density-wave fluctuations in the electrical insulator La $_{2 - x}$ Sr $_{x}$ NiO $_{4}$ . This lamellar nickelate is an isostructural analogue of the high-temperature cuprate superconductor La $_{2 - x}$ Sr $_{x}$ CuO $_{4}$ , for which recent experiments uncovered evidence for unusual structural and superconducting fluctuations indicative of rare-region physics due to inherent inhomogeneity unrelated to common point disorder effects. We find closely analogous nanoscale orthorhombic fluctuation behavior in La $_{2 - x}$ Sr $_{x}$ NiO $_{4}$ , including exponential scaling of the diffuse scattering intensity and power-law scaling of the characteristic length with relative temperature. Moreover, our neutron and x-ray scattering data reveal similar behavior for short-range magnetic and charge fluctuations above the respective ordering temperatures. These observations indicate that rare-region effects are a generic feature of perovskite-related structures and lead to universal fluctuations of both structural and electronic degrees of freedom over extended temperature ranges.

20 pages, 10 figures, supplementary material included

Evidence for rare-region physics in the structural and electronic degrees of freedom of the nickelate La2−x​Srx​NiO4​

Abstract

Evidence for rare-region physics in the structural and electronic degrees of freedom of the nickelate La $_{2 - x}$ Sr $_{x}$ NiO $_{4}$