Abstract
The superconducting (SC) phase diagram of the electron-doped cuprates has been explored by Raman spectroscopy as a function of doping x, temperature T, and magnetic field H. The data is consistent with nonmonotonic SC order parameter (OP) of the d-wave form. The persistence of SC coherence peaks in the B2g channel for all dopings implies that superconductivity is mainly governed by interactions in the vicinity of (+/-/2a, +/-/2a31) regions of the Brillouin zone. Effective upper critical field lines Hc2*{expression}(T,x) at which the superfluid stiffness vanishes and Hc22 Delta{expression}(T,x) at which the SC amplitude is suppressed by field have been determined. The difference between the two quantities suggests the presence of phase fluctuations that increase for x < 0.15. It is found that the field suppresses the magnitude of the SC gap linearly at an anomalously large rate. Hc22 Delta{expression} value that is about 10 T for optimally doped samples decreases below a Tesla for overdoped cuprates.