Photoemission and x-ray absorption spectroscopy studies on cubic pyrochlore ruthenates Bi2-xYxRu2O7

Abstract

Electronic structures of ternary pyrochlore ruthenates Bi2-xYxRu2O7 (x=0.0, 0.4, 1.0, 1.6, and 2.0) were investigated by using photoemission spectroscopy (PES) and x-ray absorption spectroscopy. The oxygen 2p band and the unoccupied conduction bands can be explained by the band calculation results, while the obtained Ru 4d partial PES spectral weight turns out to clearly show a departure from the band-structure calculation results, especially for high Y concentrations. These facts indicate that the metal-insulator transition around the composition xsimilar to1.2 is driven by the electron correlation effect among the occupied Ru 4d states.