Bulk screening in core-level photoemission from Mott-Hubbard and charge-transfer systems

Abstract

We report bulk-sensitive hard x-ray $(h\ensuremath{\nu}=5.95\phantom{\rule{0.3em}{0ex}}\mathrm{keV})$ core-level photoemission spectroscopy (PES) of single crystal ${\mathrm{V}}_{1.98}{\mathrm{Cr}}_{0.02}{\mathrm{O}}_{3}$ and the high-${T}_{c}$ cuprate ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ (Bi2212). ${\mathrm{V}}_{1.98}{\mathrm{Cr}}_{0.02}{\mathrm{O}}_{3}$ exhibits low binding energy ``satellites'' to the V $2p$ ``main lines'' in the metallic phase, which are suppressed in the antiferromagnetic insulator phase. In contrast, the Cu $2p$ spectra of Bi2212 do not show temperature-dependent features, but a comparison with soft x-ray PES indicates a large increase in the $2{p}^{5}3{d}^{9}$ satellites or $3{d}^{9}$ weight in the bulk. Cluster model calculations, including a full multiplet structure and a screening channel derived from the coherent band at the Fermi energy, give very satisfactory agreement with the experiments.