ENERGY-GAP, SUSCEPTIBILITY, AND DAMPING IN SUPERCONDUCTING CUPRATES

Anomalous damping of electrons (or holes) distinguishes cuprate superc onductors from ordinary metals. Electron-electron scattering yields th e unusual linear variation of the damping with temperature T and frequ ency omega, providing that the susceptibility exhibits scaling in omeg a/T, as in the case of a nested Fermi surface. The opening of an isotr opic energy gap of s-wave symmetry is shown to yield distinctive devia tions from scaling of the susceptibility which produce characteristic decreases in the damping below the superconducting transition temperat ure. We obtain a conductivity peak using a nesting approximation and f ind agreement with microwave experiments close to T(c).