Rigid-band shift of the Fermi level in the strongly correlated metal: Sr_2−yLa_yRuO₄

We report a systematic study of electron doping of Sr2RuO4 by nonisovalent substitution of La3+ for Sr2+. Using a combination of de Haas-van Alphen oscillations, specific heat, and resistivity measurements, we show that electron doping leads to a rigid-band shift of the Fermi level corresponding to one doped electron per La ion, with constant many-body quasiparticle mass enhancement over the band mass. The susceptibility spectrum is substantially altered and enhanced by the doping but this has surprisingly little effect on the strength of the unconventional superconducting pairing