Effects of magnetic impurities on twoband superconductor.pdf

Effects of paramagnetic impurities on two-band superconductor G.A. Ummarino∗ INFM-Dipartimento di Fisica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy 7 I calculated the effect of magnetic impurities on the normal and superconductive properties of a 0 multiband s-wave superconductor by direct solution of the two-band Eliashberg equations. In this 0 way I determined the critical temperature, the values of the superconductive gaps, the shape of the 2 superconductive density of states and other physical quantities that depend on the concentration of r magnetic impurities. I found that the gaps and the penetration lengths display an unusual behaviour a as a function of temperature. I examine the possibility that the presence of a negative induced gap M raises the critical temperature. 8 PACS numbers: 74.45.+c, 74.70.Ad, 74.20.Fg ] n A specific, but representative case of anisotropic su- where θ is the Heaviside function, ωc is a cut-off energy o perconductivity is multiband superconductivity where and Λij (iωn − iωm ) = +∞ dωα2 F (ω )/[(ωn − ωm )2 + c 0 ij r- the order parameter is different in different bands. The 2 j 2 2 j ω ], N (iω ) = ∆ (iω )/ ω + ∆ (iω ), N (iω ) = more famous and clear case is the magnesium diboride [1] ∆ m j