Intrinsic Nanoscale Disorder and the Physical Properties of HTSC

Recent STM studies revealed nanoscale electronic disorder on the crystal surface in many cuprates. In BSCCO, strong correlations between oxygen defect distributions on its surface and both the gap map and the coherence peak amplitude showed that the off-center distortions in the positions of oxygen atoms are responsible for most of the electronic disorder. How do these nanoscale inhomogeneities affect the bulk macroscopic physical properties (such as transport properties) of these compounds? What is the effect of a local oxygen disorder on these properties? Persistent circulating supercurrents, which are known to bypass regions of a reduced order parameter (macroscopic crystal defects), have been used to investigate superconducting properties. Our investigations identified universal (sample independent) features in these properties (such as Josephson effects, filamentary and percolative flow of the transport current, etc.) which can be attributed to the presence of a nanoscale inhomogeneity. Local oxygen redistribution, induced either by careful low temperature annealing or by room temperature aging, was found to modify substantially both the superconducting and the normal state properties.