Temperature-dependent XAFS study of the local lattice distortion of the CuO2 plane in Sr2CuO3+δ powder sample

Abstract

In order to study the relationship between local lattice distortion and superconductivity, we performed temperature dependent x-ray absorption fine structure (XAFS) on Sr2CuO3+δ powder sample (single phase with Tc=48 K). The temperature dependent Debye-Waller factor of Cu-O pair appears an anomalous upturn at 90 K and becomes drop around the superconducting transition temperature of ∼50 K. It means that local lattice distortion appears at 90 K. Furthermore, the analysis of temperature dependent X ray Absorption Near Edge Structure (XANES) shows that the R factor, which denotes the inhomogeneous charge density distribution, shows a sharp drop at 90 K. According to previous reports on other doped 214 cuprates, the above experimental results reveal that the local lattice distortion at Cu site in CuO2 plane occurs with the inhomogeneous charge density distribution at 90 K. It indicates that the inhomogeneous charge density distribution may be caused by the local lattice distortion at Cu site before superconductive order formation, implying that electron-lattice interaction play a key role in superconductivity of Sr2CuO3+δ.