Frequency dependence of the penetration depth of an electric field in a superconductor
Abstract
Equations of a two-fluid model of superconductivity are formulated describing the dynamics of nonzero-gap superconductors near the critical temperature Tc. Making use of this model, we consider the problem of the penetration of a longitudinal electric field into a superconductor and the collective oscillations of the phase of the order parameter. The conversion mechanism of normal excitations into Cooper pairs (the branch-mixing mechanism) associated with the interaction of electrons with collective oscillations which leads to a temperature independent electric-field penetration depth Λ is discussed. The frequency dependence of Λ calculated in the paper permits the determination of the conversion time, which decreases as Tc is approached.