Doping evolution of the chemical potential, spin-correlation gap, and charge dynamics of Nd2-xCexCuO4

We report an optical reflectivity study on Nd2-xCexCuO4 over a broad doping range 0 <= x <= 0.20. The study reveals a systematic shift of the chemical potential with doping. A pronounced peak structure specific to the electron-doped cuprate is observed in the optical scattering rate based on the extended Drude model analysis. The energy scale of the peak could be very different from that of the peak in conductivity spectrum. We clarify that the hot spots gap probed in photoemission experiments is more closely related to the sharp suppression feature in scattering rate than in conductivity spectra. The gap is associated with the short-range antiferromagnetic correlation, and disappears in a manner of fading away with increasing doping and temperature. In the heavily overdoped region, a dominant omega(2)-dependence of the scattering rate is identified up to very high energy.