Lattice Instability in High Temperature Superconducting Cuprates and FeAs Systems: Polarons Probed by EXAFS

Figure 4

Mean-square relative displacement of the Cu-O bond in superconducting La_1−𝑥Sr_𝑥CuO₄ (𝑥=0.15) with the in-plane (E//𝑎𝑏) and out-of-plane (E//c) geometries as a function of temperature. Closed and open circles denote the results for Cu-O_p (in-plane oxygen) measured for superconducting and nonsuperconducting samples (prepared by doping 3% Ni), respectively. Closed squares represent the mean-square oxygen displacement for the Cu-O_ap (out-of plane oxygen) in superconducting LSCO. Data were taken from [11].