  X-ray absorption spectroscopy (XAS) and high resolution X-ray diffraction are
combined to study the interplay between electronic and lattice structures in
controlling the superconductivity in cuprates with a model charge-compensated
CaxLa1-xBa1.75-xLa0.25+xCu3Oy (0<x<0.5, y=7.13) system. In spite of a large
change in Tc, the doped holes, determined by the Cu L and O K XAS, hardly show
any variation with the x. On the other hand, the CuO2 plaquette size shows a
systematic change due to different size of substituted cations. The results
provide a direct evidence for the chemical pressure being a key parameter for
controlling the superconducting ground state of the cuprates.
