Effects of strong coupling on pairing fluctuations in layered superconductors

The influence of short inelastic lifetimes due to strong coupling of fermio nic quasiparticles to bosons on superconducting fluctuation effects above T -c is calculated. Considering a strong-coupling model for a layered superco nducting metal, it is shown that pairing fluctuation corrections to the spi n-lattice relaxation rate in weak coupling and very strong coupling are qua litatively different if the pairing fluctuation spectrum has s-wave symmetr y. For weak coupling the corrections are positive, whereas for very strong coupling lambda = 2 integrald omega alpha F-2(omega)/omega > 2 the correcti ons are negative. In contrast, the Pauli spin susceptibility is insensitive to strong-coupling corrections.