The gap maximum of anisotropic superconductors
Laboratoire de Physique Statistique de l'Ecole Normale Supérieure, associé au CNRS et aux Universités Paris 6 et Paris 7 - 24 rue Lhomond, 75005 Paris, France
Accepted: 27 July 1998
For a completely general anisotropic order parameter (including changes of sign), we show that weak-coupling theory is incompatible with high values of the maximum of the zero-temperature gap as compared to the critical temperature Tc, such as those found experimentally in where . This gives evidence for strong-coupling effects. In particular this comes as a major support for a spin fluctuation mechanism with strong coupling, if one assumes that only a repulsive pairing interaction is at work in high- superconductors.
PACS: 74.20.Fg – BCS theory and its development / 74.25.Jb – Electronic structure / 74.72.Bk – Y-based cuprates
© EDP Sciences, 1998