Core-level electronic states of the ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{y}}$${\mathrm{Br}}_{\mathit{x}}$ superconductor, tetragonal, and orthorhombic ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{z}}$, and ${\mathrm{BaBr}}_2$ have been studied with use of x-ray photoelectron spectroscopy. The intensity ratio of the satellite to Cu 2${\mathit{p}}_{3/2}$ line increases from 0.31 for the nonsuperconducting tetragonal phase to 0.46 for the brominated superconductor sample. The latter value is close to that for the superconducting orthorhombic phase (0.51), which strongly suggests that holes are doped by bromination into the tetragonal phase. Comparison of the binding energies of Ba 3${\mathit{d}}_{5/2}$ and Br 3d for the brominated sample with those of ${\mathrm{BaBr}}_2$ shows that bromine in the former sample is strongly interacting with barium. The mechanism for the recovery of the superconductivity is discussed in terms of hole doping.

• Received 17 August 1992

DOI:https://doi.org/10.1103/PhysRevB.47.418