Nanolevel studies of lattice defects and electronic structure of YBa2Cu3O7 single crystals doped with praseodymium: Destruction of superconductivity

Scanning tunnelling microscopy and spectroscopy studies, at atomic-level resolution, have been carried out on single crystals of Y 1-x Pr x Ba 2 Cu 3 O 7 (Y(Pr)-123) to understand the striking differences between the behaviours of Pr-123 and Y-123, both having an identical crystal structure. With the incorporation of Pr, the twin-boundary density becomes systematically reduced, which is found to be consistent with the observed decrease in the orthor-hombocity. Furthermore, Pr substitution at the Y site produces a striking effect on the defect structure as well as on the electronic structure of CuO 2 planes, where superconductivity is believed to reside. The peculiar features and their impact on superconductivity are found to fit in the general framework of the explanation proposed by Blackstead et al. (1996, Phys. Rev. B, 54, 6122) and Mazin, where the disorder plays a crucial role in the suppression of superconductivity.