Local structure of high temperature superconductors from x-ray absorption studies

Abstract

Considerable effort has been devoted to determining the mechanism responsible for the electron pairing in the perovskite-structured oxide superconductors. Different measurements have provided conflicting evidence on structural instabilities and phonon anomalies in these systems. X-ray absorption fine structure (XAFS) provides a structural probe that can accurately characterize the local structure and dynamical behavior of the component atoms. Here we summarize XAFS results on YBa2Cu3O7-δ and compare and contrast these results with those on a system that exhibits charge density wave fluctuations, namely, the perovskite-structured, oxide superconductors Ba(Pb1-xBix)O3 and (Ba1-xKx)BiO3. Emphasis is placed on structural results that may shed some light on possible mechanisms of superconductivity in these systems.