Intrinsic Local Structure Anisotropy of Bi2Sr2CaCu2O 8+δ Superconductor Probed by Polarized X-Ray Absorption Spectroscopy.

We have investigated the local structure of Bi 2 Sr 2 CaCu 2 O 8 + δ 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 CuO 4 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 Bi 2 Sr 2 CaCu 2 O 8 + δ , emphasizing the importance of local structural effects in shaping the electronic phase diagram of high- T c cuprates.