Is Δπ-gap-only superconductivity possible in Mg 1− xAl xB 2 and Mg(B 1− yC y) 2 alloys?

Abstract

Using density-functional-based method, we study the k-resolved σ- and π-band holes in Mg 1− x Al x B 2 and Mg(B 1− y C y ) 2 alloys. We find that the calculated profiles of the loss of σ- and π-band holes in these two systems as a function of impurity concentration are in qualitative agreement with experiments, as expected. We also describe its implications vis- a- vis superconductivity in Mg 1− x Al x B 2 and Mg(B 1− y C y ) 2. Based on our results, a Δ π-gap-only superconductivity seems unlikely in Mg 1− x Al x B 2 alloys.