Suppression of superconductivity at the nanoscale in chemical solution derived YBa₂Cu₃O_7- thin films with defective...

The analysis of the microstructure and superconducting behavior of chemical solution deposited epitaxial YBa₂Cu₃O_7- films, with thickness going down to 5 nm has been carried out with the purpose to disclose the behavior of the most common intergrowth in these films, the Y₂Ba₄Cu₈O₁₆. The analysis of ultrathin films is a unique opportunity to investigate the superconducting behavior of these nanoscale defects because of the high concentration created as a consequence of the elastic energy associated to the misfit strain. Magnetic susceptibility and X-ray diffraction measurements evidence a strong decrease of the superconducting volume correlated with an increase of the intergrowth volume fraction. We demonstrate that these intergrowths are non-superconducting nanoscale regions where Cooper pair formation is disrupted, in agreement with their key role as artificial pinning centers for vortices in YBa₂Cu₃O_7- films and coated conductors.