Asymmetrical effects of copper-site holes versus oxygen-site holes in La-Sr-Cu-O

Abstract

The effects of the copper-site holes and oxygen-site holes on structure, superconductivity, and normal state in ${\mathrm{La}}_{1.85}$ ${\mathrm{Sr}}_{0.15}$ ${\mathrm{CuO}}_4$ have been studied by use of a method in which the hole concentrations at both sites are varied independently. The filling of the ${\mathrm{Cu}}^{2+}$ holes and the ${\mathrm{O}}^{\mathrm{-}}$ holes induces a tetragonal-to-orthorhombic structural transition. Such a behavior strongly supports the interpretation that the driving force for the bending of Cu-O-Cu bonds is the stabilization of the ${\mathrm{\sigma }}^{\mathrm{*}}$ antibonding interaction. The two hole-filling processes generate profoundly different effects on ${\mathit{T}}_{\mathit{c}}$ normal-state transport, and magnetic susceptibility. We will discuss the causes of these highly asymmetrical effects.