Pair-breaking effects in high-temperature superconductors

We assume strong dynamic pair breaking to be responsible for some of the superconducting properties of the high-Tc materials. Using the theory of superconductors containing paramagnetic impurities, we solve the equation for the temperature-dependent energy gap with a frequency-dependent self-energy, whose ω dependence is obtained by two independent ways: a ''direct'' procedure using the experimental data of the Raman scattering intensity in the superconducting state and an ''indirect'' procedure relating the self-energy in the superconducting state to that of the normal state via the dynamical scattering rate. We assume ''marginal-Fermi-liquid'' behavior for the frequency dependence of the self energy. We obtain a non-BCS-like temperature dependence of the gap Δ(T), which remains nearly constant below Tc and drops almost discontinuously to zero at Tc, with a ratio 2Δ(0)/kTc of up to 8. These results are used to give a qualitative explanation of experimental findings, such as tunneling, infrared, photoemission, and Raman spectroscopy. In addition, the direct procedure predicts gapless superconductivity