Nernst effect in the electron-doped cuprate superconductor La2-xCexCuO4

We report a systematic study of the Nernst effect in films of the electron-doped cuprate superconductor La2-xCexCuO4 as a function of temperature and magnetic field (up to 14 T) over a range of doping from underdoped (x = 0.08) to overdoped (x = 0.16). We have determined the characteristic field scale H*(C2) of superconducting fluctuation which is found to track the domelike dependence of superconductivity (T-C). The fall of H*(C2) and T-C with underdoping is most likely due to the onset of long-range antiferromagnetic order. We also report the temperature onset, T-onset, of superconducting fluctuations above T-C. For optimally doped x = 0.11 Tonset (congruent to 39K) is high compared to T-C (26 K). For higher doping T-onset decreases and tends to zero along with the critical temperature at the end of the superconducting dome. The superconducting gap closely tracks H*(C2) measured from the temperature-and field-dependent Nernst signal.