Photoemission study of single-crystal Bi2Sr1.9Pr0.1CuO6+ delta.

Abstract

We performed exploratory angle-integrated and angle-resolved photoemission-spectroscopy measurements on Pr-stabilized single crystals of ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CuO}}_{6}$ (${\mathit{T}}_{\mathit{c}}$\ensuremath{\sim}10 K). Fermi-level crossings along principal directions match some crossings predicted by tight-binding calculations. These crossings differ from both the Fermi-surface mapping and the local-density-approximation-derived Fermi surfaces on the much studied ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{Ca}}_{1}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ (${\mathit{T}}_{\mathit{c}}$\ensuremath{\sim}75--96 K). We observe optical-polarization effects in the angle-resolved spectra, which is consistent with the states near ${\mathit{E}}_{\mathit{F}}$ being derived from the orbitals containing ${\mathit{d}}_{\mathit{x}}^{2}$-${\mathit{y}}^{2}$ symmetry. The density-of-states contribution from the Pr 4f states derived by resonant-photoemission spectroscopy suggests that the Pr 4f states do not hybridize strongly and lie away from the Fermi level, thus not affecting the superconductivity of the Bi-Sr-Ca-Cu-O system.