Intrinsic local structure anisotropy of Bi2Sr2CaCu2O 8+δ superconductor probed by polarized X-ray absorption spectroscopy

We have investigated the local structure of (Formula presented.) superconductor by Cu K-edge extended x-ray absorption fine structure (EXAFS) spectroscopy to explore the temperature-dependent local displacements and their possible relationship with the charge ordering, nematicity, and superconductivity. We have used x-ray polarization dependence of the EXAFS signal to unravel a clear local structure anisotropy, indicating a deviation from the average tetragonal symmetry. This distortion is associated with charge ordering and stripe formation in the (Formula presented.) plane. Anomalies in the Debye–Waller factor at both the charge-ordering and superconducting transition temperatures suggest a strong coupling between the local displacements and electronic degrees of freedom. The local structure anisotropy appears stronger in the interlayer, highlighted by the Cu─Sr bond correlations. These findings provide further insight into the interplay between atomic displacements, charge ordering, and superconductivity in (Formula presented.), emphasizing the importance of local structural effects in shaping the electronic phase diagram of high- (Formula presented.) cuprates.