Structural disorder and the origin of high-T-c suppression in La1.875Ba0.125CuO4

Polarized x-ray absorption fine structure (XAFS) measurements at all La, Pa and Cu sites were used to study local structural features that accompany t he strong T-c suppression at x similar to 1/8 in La2-xBaxCuO4. Two critical parameters regulating the strength of hole-lattice coupling in this materi al were determined, i.e., the direction and magnitude of CuO6 octahedra loc al tilts. Our findings include the existence of large disorder in the magni tude of the tilt angle about its average value [theta], with an rms root[de lta theta(2)] approximate to 2[theta]. We suggest that this large disorder strongly scatters a large fraction of states at the Fermi surface for x sim ilar to 1/8 leading to the observed T-c suppression.