Evidence for critical lattice fluctuations in the high Tc cuprates

Here we provide a direct experimental evidence for critical local lattice fluctuations in the high T-c superconductors. Cu K-edge extended X-ray absorption fine structure (EXAFS) has been used to measure the distribution of Cu-O bond lengths and the amplitude of local lattice distortions in different materials with increasing chemical pressure on the CuO2 layers. The stripe formation temperature T-infinity. is determined by the upturn of the Debye Waller factor due to the onset of local lattice distortions. A decrease of the amplitude of lattice fluctuations at the superconducting transition reveals their role in the pairing mechanism. The dynamical lattice fluctuations in the normal phase for T > T-infinity. show diverging lattice fluctuations at the critical chen-deal pressure epsilon (c).