Disorder and Superconductivity inA−15Compounds

The universal depression of the superconducting transition temperature $T_c$ in disordered $A-15\mathrm{}$ compounds is examined. Existing energy-band calculations are used to calculate the density of electron states, which is possibly enhanced by disorder in some cases such as ${\mathrm{Nb}}_3$Ge. The dramatic drop in $T_c$ in ${\mathrm{Nb}}_3$Ge at a critical value of the resistivity is attributed to overdamping of acoustic plasmons which decreases the electron pairing interaction despite small changes in the density of states.