Theory of superconducting contacts

Metallic contacts between superconducting and normal films are known to have a pair-breaking effect on the electron pairs. By limiting our considerations to the gapless regime and to contacts between superconducting and paramagnetic metals the features of this pair-breaking mechanism are investigated. We compute the normalization of the order parameter and with it such quantities as the tunneling conductance, electrical and thermal conductivity and the critical current parallel to the contact. Furthermore we investigate the influence of a magnetic field. By calculating the? ₂(t)-parameter we demonstrate the interplay between the different pair-breaking mechanisms in perpendicular and parallel fields. In the latter case we discuss the influence of the contact on the superconducting sheath proposed bySaint-James andde Gennes. Experiments to test the present theory are suggested.