Doping-induced charge redistribution in the high-temperature superconductor ${\mathrm{HgBa}}_2{\mathrm{CuO}}_{4+\delta }$

To understand the link between doping and electronic properties in high-temperature superconductors, we report first-principles calculations on the oxygen doping effect for the single-layer cuprate ${\mathrm{HgBa}}_2{\mathrm{CuO}}_{4+\delta }.$ We find ionic behavior of the dopant atom up to $\delta =\mathrm{0.22.}\mathrm{}$ The excess oxygen attracts electrons from the ${\mathrm{CuO}}_2$ plane leading to an increase of the hole concentration in this building block. The maximum amount of holes is reached when the dopant oxygen shell is closed. All theoretical findings are in excellent agreement with experimental observations. We propose that this doping behavior may be a characteristic feature of high-temperature superconductors with the filling of the dopant oxygen shell to be a limiting factor for the hole content in ${\mathrm{CuO}}_2$ planes. Possible effects of the charge redistribution on $T_c$ are discussed.