Nernst effect in the electron-doped cuprate superconductor La_2-<i>x</i>Ce<i>_x</i>CuO₄

We report a systematic study of the Nernst effect in films of the electron doped cuprate superconductor La_2-xCe_xCuO₄ (LCCO) 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). In addition, we also report the temperature onset, T_onset, of superconducting fluctuations above T_C. We find that for optimally doped x=0.11 the T_onset is ~ 39 K while T_C is ~ 26 K. For higher doping, the T_onset follows the superconducting dome.