Superconducting anisotropy in the electron-doped high-Tc superconductors Pr2-xCexCuO4-y

We report superconducting anisotropy measurements in the electron-doped high-T-c superconductors (HTSCs) Pr2-xCexCuO4-y (PCCO, x = 0.15 and 0.17) with an applied magnetic field (H-0) up to 28 T. Our results show that the upper critical field [H-c2(T)] of PCCO is highly anisotropic and as the temperature T -> 0, the value of it at H-0 vertical bar vertical bar c [H-c2,H- vertical bar vertical bar c (0)] is far less than the Pauli limit. The low temperature anisotropic character of PCCO is found to be rather similar to that of hole-doped cuprate HTSCs, but apparently larger than that of typical Fe-based superconductors. This study also proves a new sensitive probe of detecting rich properties of unconventional superconductors with the use of the resonant frequency of an NMR probe circuit.