Multiscale distribution of oxygen puddles in 1/8 doped YBa2Cu3O6.67
  Despite intensive research a physical explanation of high Tc superconductors remains elusive. One reason for this is that these materials have generally a very complex structure making useless theoretical models for a homogeneous system. Little is known on the control of the critical temperature by the space disposition of defects because of lack of suitable experimental probes. X-ray diffraction and neutron scattering experiments used to investigate y oxygen dopants in YBa2Cu3O 6+y lack of spatial resolution. Here we report the spatial imaging of dopants distribution in-homogeneity in YBa2Cu3O6.67 using scanning nano X-ray diffraction. By changing the X-ray beam size from 1 micron to 300 nm of diameter, the lattice inhomogeneity increases. The ordered oxygen puddles size distribution vary between 6-8 nm using 1x1 {\mu}m2 beam, while it is between 5-12 nm with a fat tail using the 300x300 nm2 beam. The increased inhomogeneity at the nanoscale points toward an intrinsic granular complexity. 
Alessandro Ricci, Nicola Poccia, Gaetano Campi, Francesco Coneri,   Alessandra Stella Caporale, Davide Innocenti, Manfred Bu...
cond-mat.supr-con cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.str-el