Anomalous scattering rate and microwave absorption in Bi₂Sr₂CaCu₂O_(8+δ) and YBa₂Cu₃O_(7-δ)

We determine the scattering rate from microwave measurements for an optimally doped Bi-2212 single crystal, using a simple two fluid model with a d-wave symmetry order parameter. In the superconducting state, the calculated scattering rate is three orders of magnitude smaller than that determined from ARPES experiments. A similar anomalously large decrease in the scattering rate is also required to explain the data within a gap-quasiparticle scenario for other HTS, such as $YBa_{2}Cu_{3}O_{7-\delta}$. The results suggest that the assumption of normal excitations vanishing at low $T$ is invalid and an additional charge mode is responsible for the microwave absorption.