Effect of impurities on the thermodynamics of A15 superconductors

Abstract
The authors have derived a model theory for the superconductivity of A15 compounds, with normal and paramagnetic impurities, which is based on a generalised version of the Eliashberg equation that includes the possibility of energy dependence in the electron density of states. This variation is simulated by a Lorentzian distribution symmetric about the chemical potential and superimposed on a constant background density. To be specific, parameters similar to those characteristic of Nb3Sn are used but with a high and narrow peak in the density of states.