Superconducting gap and pair breaking in CeRu2 studied by point contacts

Анотація

The superconducting gap in a CeRu₂ single crystal is investigated by point contacts. BCS-like behavior of the gap D in the temperature range below T_c^* (T_c ^* < T_c, where T_c is the critical temperature) is established, indicating the presence of a gapless superconductivity region (between T_c^* and 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 D^a (in the presence of paramagnetic impurities) and the gap D^p (in the pure case) for the single crystal and for the previously studied polycrystalline CeRu₂. The value 2D^p(0)»2 meV, with 2D^p(0)/k_BT_c»3.75, is found in both cases, indicating that CeRu₂ is a "moderate" strong-coupling superconductor.