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-T(c) 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 omega-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 DELTA(T), which remains nearly constant below T(c) and drops almost discontinuously to zero at T(c), with a ratio 2-DELTA(0)/kT(c) 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.