Study of temperature dependent local structure by polarized Cu K-edge EXAFS measurements on La2-xSrxCuO4 (x=0.105, 0.13, 0.20)

We have studied temperature dependent local structure of superconducting La2-xSrxCuO4 (0.105, 0.13, 0.20) single crystals by Cu K-edge extended x-ray absorption fine structure (EXAFS) measurements with polarization parallel to the in-plane Cu-O bonds. We find that, while underdoped crystals (x = 0.105, 0.13) show anomalous temperature dependence, similar to the case of optimally doped system (x = 0.15), overdoped crystal (x = 0.20) does not reveal such anomaly. Correlated Debye-Waller factor (DWF) of the Cu-O bonds (distance broadening) has been used as an order parameter to determine characteristic local displacements in the CUO2 plane. The amplitude of temperature dependent step-like increase in the DWF at low temperature decreases with increasing doping. It has been discussed that decreasing electron-lattice interaction with increasing doping, shown by angle resolved photoemission measurements, is closely related to the evolving anomalous local CUO2 distortion and charge inhomogeneity with doping in the CUO2 plane of high T-c oxides.