COMPOSITION DEPENDENCE OF THE TRANSITION TEMPERATURE AND ENERGY GAP OF SUPERCONDUCTING ALLOYS WITH NONMAGNETIC IMPURITIES

Abstract

Analytic expressions of superconducting transition temperature (T c ) and maximum energy gap (Δ0) of alloys with nonmagnetic impurities are obtained in terms of the alloy composition and the modified normal state electron density of states (DOS), assuming a Lorentzian DOS in the unalloyed state. The calculations were performed within the framework of the BCS theory. As expected, both T c and Δ0 are modified significantly from the BCS expressions. However, the nature of change depends on whether the width of the electron DOS is greater or less than the Debye energy of the alloy.