Correlating Off-Stoichiometric Doping and Nanoscale Electronic Inhomogeneity in the High-TcSuperconductorBi2Sr2CaCu2O8+δ

Abstract

A microscopic theory is presented for the observed electronic disorder in superconducting Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$. The essential phenomenology is shown to be consistent with the existence of two types of interstitial oxygen dopants: those serving primarily as charge reserviors and those close to the apical plane contributing both carriers and electrostatic potential to the CuO$_2$ plane. The nonlinear screening of the latter produces nanoscale variations in the doped hole concentration, leading to electronic inhomogeneity. Based on an unrestricted Gutzwiller approximation of the extended t-$J$ model, we provide a consistent explanation of the correlation between the observed dopant location and the pairing gap and its spatial evolutions. We show that the oxygen dopants are the primary cause of both the pairing gap disorder and the quasiparticle interference pattern.Comment: Revised version to appear in Phys. Rev. Lett. A microscopic origin of two types of dopant oxygens is discussed. 4 pages, 3 figures, revtex4 fil