Universal short-range orthorhombic correlations in two cuprate superconductors*

The high-temperature copper-oxide (cuprate) superconductors have been extensively studied for over thirty years, yet important questions regarding their phase diagram and unconventional superconductivity remain. In particular, the role of inherent structural inhomogeneity is not well understood. We carried out diffuse X-ray and neutron scattering experiments on two cuprates – La_2-xSr_xCuO₄ and Tl₂Ba₂CuO_6+δ – and observed short-range orthorhombic correlations in wide doping and temperature ranges, including compositions that maintain tetragonal average structure at low temperature. The strength of this structural precursor response exhibits exponential temperature scaling. Similar exponential behavior was seen in the superconducting precursor of cuprates [1,2] and other oxides [3]. This points to the relevance of structural inhomogeneity for the emergence of superconductivity and is consistent with a recent phenomenological model for the cuprates [4].

[1] D. Pelc et al., Nat. Commun. 9, 4327 (2018)
[2] G. Yu et al., Phys. Rev. B. 99, 214502 (2019)
[3] D. Pelc et al., Nat. Commun. 10, 2729 (2019)
[4] D. Pelc et al., Sci. Adv. 5, eaau4538 (2019)