Unusual short-range structural fluctuations in La2-xSrxCuO4 and La2-xSrxNiO4

Understanding the connection between structural and electronic properties in complex oxides is of fundamental importance. Our recent x-ray and neutron scattering measurements of the high-Tc superconductors La2-xSrxCuO4 and Tl2Ba2CuO6+δ revealed unusual scaling behavior of short-range orthorhombic fluctuations across the temperature-doping phase diagram, including for nominally tetragonal compositions [1]. In particular, we observe an exponential dependence of the scattering intensity on absolute (rather than reduced) temperature, analogous to recent findings for the superconducting precursor of cuprates and other oxides [2]. Here we report on efforts to extend these measurements to higher temperatures for La2-xSrxCuO4 and to the isostructural insulating nickelate La2-xSrxNiO4. Our results suggest that structural fluctuations are necessary to understand the electronic properties of these materials, and they point to the pivotal importance of underlying structural inhomogeneity and to a possible connection with Urbach (or Lifshitz) tails previously observed near the optical band edge in various amorphous, disordered, and crystalline materials [3].



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

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

[3] F. Urbach, Phys. Rev. 92, 1324 (1953).



Work supported by the U.S. Department of Energy through the University of Minnesota Center for Quantum Materials, under Grant No. DE-SC0016371.