Doping Dependence of an n -Type Cuprate Superconductor Investigated by Angle-Resolved Photoemission Spectroscopy

We present an angle-resolved photoemission doping dependence study of the n-type cuprate superconductor Nd_2-xCeₓCuO_4±δ, from the half-filled Mott insulator to the Tc0ex0ex=0ex0ex24K superconductor. In Nd₂CuO₄, we reveal the charge-transfer band for the first time. As electrons are doped into the system, this feature's intensity decreases with the concomitant formation of near- EF spectral weight. At low doping, the Fermi surface is an electron-pocket (with volume ~x) centered at (π,0). Further doping leads to the creation of a new holelike Fermi surface (volume ~1+x) centered at (π,π). These findings shed light on the Mott gap, its doping evolution, as well as the anomalous transport properties of the n-type cuprates.