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

Abstract

Polarized x-ray absorption fine structure (XAFS) measurements at all La, Ba and Cu sites were used to study local structural features that accompany the strong Tc suppression at x ∼ 1/8 in La2-xBaxCuO4. Two critical parameters regulating the strength of hole-lattice coupling in this material were determined, i.e., the direction and magnitude of CuO6 octahedra local tilts. Our findings include the existence of large disorder in the magnitude of the tilt angle about its average value 〈θ〉, with an rms √〈δθ2〉 ≈ 2〈θ〉. We suggest that this large disorder strongly scatters a large fraction of states at the Fermi surface for x ∼ 1/8 leading to the observed Tc suppression.