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We have performed photoemission and soft x-ray absorption studies ofpyrochlore-type Ru oxides, namely, the filling-control systemSm$_{2-x}$Ca$_x$Ru$_2$O$_7$ and the bandwidth-control systemSm$_{2-x}$Bi$_x$Ru$_2$O$_7$, which show insulator-to-metal transition withincreasing Ca and Bi concentration, respectively. Core levels and the O 2$p$valence band in Sm$_{2-x}$Ca$_x$Ru$_2$O$_7$ show almost the same amount ofmonotonous upward energy shifts with Ca concentration, which indicates that thechemical potential is shifted downward due to hole doping. The Ru 4$d$ band inSm$_{2-x}$Ca$_x$Ru$_2$O$_7$ is also shifted toward the Fermi level ($E_F$) withhole doping and the density of states (DOS) at $E_F$ increases. The core levelsin Sm$_{2-x}$Bi$_x$Ru$_2$O$_7$, on the other hand, do not show clear energyshifts except for the Ru 3$d$ core level, whose line shape change also reflectsthe increase of metallic screening with Bi concentration. We observe pronouncedspectral weight transfer from the incoherent to the coherent parts of the Ru 4d$t_{2g}$ band with Bi concentration, which is expected for a bandwidth-controlMott-Hubbard system. The increase of the DOS at $E_F$ is more abrupt in thebandwidth-control Sm$_{2-x}$Bi$_x$Ru$_2$O$_7$ than in the filling-controlSm$_{2-x}$Ca$_x$Ru$_2$O$_7$, in accordance with a recent theoreticalprediction. Effects of charge transfer between the Bi 6$sp$ band and the Ru4$d$ band are also discussed.Comment: 11 pages, 6 figure

Evolution of the electronic structure across the filling-control and bandwidth-control metal-insulator transitions in pyrochlore-type Ru oxides