Temperature Dependent Local Instability of the Hg1212 Structure by Polarized EXAFS

The local structure of the H gl Ba 2 CaCu 2 O 6+δ (Hg1212) crystal has been investigated by temperature dependent polarized Cu K-edge extended x-ray absorption fine structure (EXAFS). We have observed an anomalous behavior of the local structure showing anomaly at around the superconducting transition temperature T c in the temperature dependence of the Cu-O(planar) distance. The result suggests similarity of the temperature dependent local instability in the superconducting cuprates.