Schedule Apr 26, 2000
Imaging the Effects on Superconductivity of Individual Impurity Atoms
Professor J. C. Seamus Davis, University of California, Berkeley
Dr. Davis will describe his recent studies of the High-TC Superconductor BiSrCaCuO, using a high resolution very low temperature STM, in which single impurity atoms were used to probe the structure of the superconducting order parameter and the correlation between electrons. Quasiparticle scattering at impurities generates localized impurity states at the atmoic scale. Imaging these impurity states with individual (non-magnetic) Zinc dopant atoms at the Copper site in the Copper-Oxide plane shows several direct real-space consequences of the d-wave nature of the order parameter. The spectra are in qualitative agreement with d-wave BCS theories of non-magnetic quasiparticle scattering at a single impurity atom. The destruction of superconductivity within 1.5 nm of the Zn sites is observed. He will also discuss very new results of imaging of the impurity states associated with individual Nickel dopant atoms (magnetic) substituted at the Copper site, which show numerous new atomic-scale phenomena which, although partially consistent with theory for magnetic impurity atom scattering in a d-wave BCS context, are not fully described by existing theories.

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