Normal-state Nernst effect in electron-doped Pr2-xCexCuO4-δ:: Superconducting fluctuations and two-band transport

We report a systematic study of the normal-state Nernst effect in the electron-doped cuprates Pr2-xCexCuO4-delta over a wide range of doping (0.05 <= x <= 0.21) and temperature. At low temperatures, we observed a notable vortex Nernst signal above T-c in the underdoped films, but no such normal-state vortex Nernst signal is found in the overdoped region. The superconducting fluctuations in the underdoped region are most likely incoherent phase fluctuations as found in hole-doped cuprates. At high temperatures, a large normal-state Nernst signal is found at dopings from slightly underdoped to highly overdoped. Combined with normal-state thermoelectric power, Hall effect, and magnetoresistance measurements, the large Nernst effect is compatible with the two-band model. For the highly overdoped films, the large Nernst effect is anomalous and not explainable with the simple holelike Fermi surface seen in photoemission experiments.