Angle-resolved photoemission study of the metal-insulator transition in bismuth cobaltates

We present an angle-resolved photoemission spectroscopy study of a Mott-Hubbard-type bismuth cobaltate system across a metal-insulator transition. By varying the amount of Pb substitution and by doping with Sr or Ba cation, a range of insulating to metallic properties is obtained. The electronic structure shows the emergence of a weakly dispersing state at the Fermi energy with increasing conductivity. A systematic change in the spectral weight of the coherent and incoherent parts, accompanied by an energy shift of the incoherent part, is also observed. The changes may be correlated with changes in the temperature-dependent resistivity. The nature of the coherent-incoherent components is compared to the peak-dip-hump feature seen in cuprate superconductors.