INTRINSIC NANOSCALE DISORDER IN HTSC: EFFECT ON THE PHYSICAL PROPERTIES

Abstract

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. Additional information on nanoscale inhomogeneities and its relationship to the lattice strain and oxygen redistribution can be obtained from the electrical transport that uses Percolating Persistent Supercurrents which are known to bypass regions of a reduced order parameter (macroscopic crystal defects). Our investigations identified universal (sample independent) features in the superconducting properties which can be attributed to the presence of a nanoscale inhomogeneity, such as nanogranular Josephson effects, strain-induced filamentary and percolative flow of the transport current, etc. Local oxygen redistribution, induced either by careful low temperature annealing or by room temperature aging, modifies both the superconducting and the normal state properties.