Local electronic structure of near oxygen dopants: a window on the high-Tc pairing mechanism.

The cuprate material (Bi(2)Sr(2)CaCu(2)O-2212) is believed to be doped by a combination of cation switching and excess oxygen. The interstitial oxygen dopants are of particular interest because scanning tunneling microscopy (STM) experiments have shown that they are positively correlated with the local value of the superconducting gap, and calculations suggest that the fundamental attraction between electrons is modulated locally. In this work, we use density functional theory to try to ascertain which locations in the crystal are energetically most favorable for the O dopant atoms, and how the surrounding cage of atoms deforms. Our results provide support for the identification of STM resonances at -1 with dopant interstitial O atoms, and show how the local electronic structure is modified nearby.