RELAXATION AND ELECTROMAGNETIC RESPONSE OF A SUPERCONDUCTOR IN A STATE OF SUPERCURRENT FLOW

The situation is investigated in which a superconductor in a state of supercurrent flow and near the transition temperature is exposed to an alternating electric field. The induced alternating current is shown to exhibit a frequency dependence (1-iΩτR)-1, which is due to a relaxation process in the Cooper-pair density. The relaxation time τR is determined by electron-phonon collisions (collision time τc), in which case τRτc[Tc(Tc-T)]12; impurity scattering is important only under certain conditions, in which case τR10-11[Tc(Tc-T)]-5 sec. © 1969 The American Physical Society.