Is Δπ-gap-only superconductivity possible in Mg1−xAlxB2 and Mg(B1−yCy)2 alloys?

Using density-functional-based method, we study the k-resolved σ- and π-band holes in Mg1−xAlxB2 and Mg(B1−yCy)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 Mg1−xAlxB2 and Mg(B1−yCy)2. Based on our results, a Δπ-gap-only superconductivity seems unlikely in Mg1−xAlxB2 alloys.