Superconducting gap and pair breaking in CeRu2 studied by point contacts

The superconducting gap in a CeRu2 single crystal is investigated by point contacts. BCS-like behavior of the gap Delta in the temperature range below T-c* (T-c*<T-c, where T-c is the critical temperature) is established, ind icating the presence of a gapless superconductivity region (between T-c* an d T-c). The pair-breaking effect of paramagnetic impurities, supposedly Ce ions, is taken into consideration using the Scalski-Betbeder-Matibet-Weiss approach based on Abrikosov-Gorkov theory. It allows us to recalculate the superconducting order parameter Delta (alpha) (in the presence of paramagne tic impurities) and the gap Delta (p) (in the pure case) for the single cry stal and for the previously studied polycrystalline CeRu2. The value 2 Delt a (p)(0) approximate to 2 meV, with 2 Delta (p)(0)/k(B)T(c) approximate to 3.75, is found in both cases, indicating that CeRu2 is a "moderate" strong- coupling superconductor. (C) 2001 American Institute of Physics.