## Abstract

The linearized Eliashberg theory for dirty superconductors in the vicinity of T_{c} is used to generate the dynamic Ginzburg-Landau (GL) equation for the order parameter and the coupled Boltzmann equation for the quasi-particle distribution function, with and without magnetic impurities and inelastic phonon scattering. The Schmid and Schön (SS) separation of the order parameter into longitudinal (real) and transverse (imaginary) components is shown to be exact to linear order. The former does not couple with the wave vector (k) and frequency (ω) dependent external field, while the latter does. Explicit expressions are exhibited for the current and charge densities to leading order [ Δ T in the gap regime, in which Δτ_{s} > 1 where τ_{s} is the conduction electron spin flip lifetime; and Δ^{2} T(ω + iDk^{2}) in the gapless regime, Δτ_{s} < 1. D is the diffusion constant]. The continuity equation is shown to be obeyed to this order. Use of the Poisson equation in relation to the transverse component leads to a propagating mode, which, in the absence of magnetic impurities, reduces to the SS result. We find that the mode propagates only in the gap regime, whereas it is purely diffusive in the gapless regime and for gapless superconductors. In the presence of magnetic impurities, the solution reduces to the SS limit, but with reduced mode velocity and damping. The charge density appropriate to the propagating mode is shown to be zero to order ω ω_{p}^{2}τ_{1}, where τ_{1} is the impurity scattering time and θ_{p} the plasma frequency. The characteristic penetration length of an electric field into a superconductor is calculated, taking into account the phonon inelastic scattering time. The result reproduces the Waldram and SS expressions. Careful examination is made of the conditions under which these results pertain. The characteristic penetration length is also obtained in the gapless regime and for gapless superconductors for which T_{c}τ_{s} < 1. Finally, the longitudinal and transverse pair susceptibilities are calculated with and without magnetic impurities and in the gap and gapless regimes.

Original language | English |
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Pages (from-to) | 35-76 |

Number of pages | 42 |

Journal | Annals of Physics |

Volume | 116 |

Issue number | 1 |

DOIs | |

State | Published - 1 Jan 1978 |

Externally published | Yes |

## ASJC Scopus subject areas

- Physics and Astronomy (all)

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