Dynamic inhomogeneities in the La2CuO4-based superconductors

Polarization-dependent X-ray-absorption fine-structure (XAFS) measurements on the local structure of the La2CuO4-based high-T-c superconductors La2-xSrxCuO4, La2-xBaxCuO4, and La1.6-xSrxNd0.4CuO4 find, among others, orientation disorder induced in the Cu-O-2 planes by doping Sr, Ba, and alloying Nd atoms, all such atoms residing in La-sites. The orientation disorder is of two types: mostly static-buckling disorder, and dynamic disordering of the tilt angles of the Cu-O-6 octahedra correlated in nanoscale regions, with respect to neighboring nanoscale regions. Buckling disorder in the Cu-O-2 planes has the greatest detrimental effect on T-c and conductivity for such foreign atoms.