Positive Hall coefficient observed in single-crystal Nd2-xCexCuO4- at low temperatures

The Hall coefficient RH has been measured in superconducting single crystals of Nd2-xCexCuO4-(x0.15). Although RH is sample dependent in sign above 100 K, it increases steeply to positive values in all crystals studied below 80 K. RH remains T (temperature) dependent at 2 K, in contrast to the resistivity a which saturates to a constant below 30 K. Using a two-band model, we account for the observed profiles of RH vs T and a vs T. The analysis reveals that the scattering processes for the electronlike and holelike bands have vastly different temperature scales. The hole-scattering rate remains T dependent to 2 K. The question whether the hole or the electron quasiparticles are responsible for the superconductivity in Nd2-xCexCuO4- is discussed.