Sum rule anomaly from suppression of inelastic scattering in the superconducting state

In the conventional BCS description of a superconductor, the kinetic energy increases in the superconducting state. We describe the observed decrease in kinetic energy by adopting a simple model of electrons with a frequency-independent scattering that undergoes a sharp decrease as the temperature is lowered below T-c. This phenomenology has been suggested by other experiments, particularly microwave conductivity. We find that such a decrease accounts for the observed decrease in kinetic energy; a study of these different phenomena over a wide range of high T-c materials would confirm this correlation.