Critical fields, Pauli paramagnetic limiting, and material parameters ofNb3Sn andV3Si

Abstract

The upper-critical-field behavior of ${\mathrm{Nb}}_3$Sn and ${\mathrm{V}}_3$Si is studied as a function of residual resistivity. The results are analyzed in the framework of the Ginzburg-Landau-Abrikosov-Gor'kov theory of type-II superconductivity including the effects of the electron-phonon interaction. The importance of the electron-phonon interaction on the Pauli paramagnetic limiting process is stressed and it is found that inclusion of the electron-phonon corrections (most importantly the electron-phonon renormalization of the normal-state parameters) is needed to sensibly fit the data. For ${\mathrm{Nb}}_3$Sn failure to include these effects leads to too high spin-orbit scattering rates. The critical-field data are also used to determine the density of states of these materials as well as several other superconducting and normal-state parameters.