title: Origin of the spatial variation of the pairing gap in bi-based high temperature cuprate superconductors.
abstract: Recently, scanning tunneling microscopy on the Bi-2212 cuprate superconductor has revealed a spatial variation of the energy gap that is directly correlated with a modulation of the apical oxygen position. We identify two mechanisms by which out-of-plane oxygens can modulate the pairing interaction within the CuO2 layer: a covalency between the x2-y2 band and apical p orbital, and a screening of correlation U by apical oxygen polarization. Both effects strongly depend on the apical oxygen position, and their cooperative action explains the experiment.
authors.affiliation: Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Michiyasu
authors.initials: M
authors.lastname: Mori
authors.forename: Giniyat
authors.initials: G
authors.lastname: Khaliullin
authors.forename: Takami
authors.initials: T
authors.lastname: Tohyama
authors.forename: Sadamichi
authors.initials: S
authors.lastname: Maekawa