PUB - Publikationen an der Universität Bielefeld

The problem of identifying the pairing mechanism in high-T c superconductors is discussed. The pairing interaction in a superconductor cannot be measured directly by experiment, but can only be seen through its effects on different observable properties. These difficulties are discussed first for the conventional superconductors and it will be shown how the electron-phonon interaction can be identified as the pairing mechanism in this case using controlled approximations. For the high-T c superconductors the situation is much more difficult because of the complexity of these materials and the lack of accurate theories. Recent studies of the spinfluctuation mechanism within the FLEX-approximation are reviewed and it is shown that this mechanism has a number of features, which are qualitatively different from the conventional phonon mechanism, but have similarities with observations on the high-T c compounds.