Superconducting anisotropy in the electron-doped high-T c superconductors

We report superconducting anisotropy measurements in the electron-doped high-Tc superconductors (HTSCs) Pr2−xCexCuO4−y (PCCO, x = 0.15 and 0.17) with an applied magnetic field (H0) up to 28 T. Our results show that the upper critical field [Hc2(T )] of PCCO is highly anisotropic and as the temperature T → 0, the value of it at H0 � c [Hc2,� 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.