Origin of the spatial variation of the pairing gap in bi-based high temperature cuprate superconductors.
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.
Mori
Michiyasu
M
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Khaliullin
Giniyat
G
Tohyama
Takami
T
Maekawa
Sadamichi
S