Photoemission spectral weight transfer and mass renormalization in the Fermi-liquid system La_1-xSr_xTiO_3+y/2

We have performed a photoemission study of La_1-xSr_xTiO_3+y/2 near the filling-control metal-insulator transition (MIT) as a function of hole doping. The spectral intensity at the chemical potential (μ) and the mass enhancement factor deduced from the bandwidth show qualitatively the same doping dependence as the specific coefficient γ except for near the MIT, where additional mass renormalization may occur in the vicinity of μ. Upon antiferromagnetic ordering, spectral weight transfer occurs from the coherent to the incoherent parts, which we associate with the partial gap opening at μ.