Magnetic-field-induced pair-breaking effects in granular Pb films near the superconductor-to-insulator transition

We have measured the magnetic-field dependence, 0H8 T, of the resistive transitions R(T) of ultrathin granular superconducting Pb films with normal-state sheet resistances, RQRN100 k, where RQ=h/4e26.45 k. The data suggest that the magnetic-field-induced superconductor-to-insulator transition in these films occurs in a field regime where pair-breaking effects have significantly reduced the amplitude of the superconducting order parameter. We compare our results with those obtained on systems with uniform morphologies.