TEMPERATURE-DEPENDENT CU-O DISTRIBUTION FUNCTION OF THE SUPERCONDUCTING CUO2 PLANE

The temperature-dependent pair distribution function of the in plane C u-O pairs has been determined by in plane polarized (E parallel to ab) Cu K-edge extended X-ray absorption fine structure (EXAFS) experiment s on single crystal of La1.85Sr0.15CuO4 (LSCO) with T-c=35 K. A splitt ing of the Cu-O (planar) distance larger than the correlated Debye-Wal ler factor appears for T<100 K. The separation between the two distanc es decreases at T-c but increases again in the superconducting state ( T<T-c), The comparison with diffraction data probing the uncorrelated Debye-Waller factors is discussed.