Low-temperature resistivity of ordered and disorderedA15compounds

Abstract

The low-temperature electrical resistivity has been measured for the high-$T_c$ $A15\mathrm{}$ compounds ${\mathrm{Nb}}_3$Sn, ${\mathrm{Nb}}_3$Al, and ${\mathrm{Nb}}_3$Ge and also a low-$T_c$ compound ${\mathrm{Mo}}_3$Ge. It is found that most of the high-$T_c$ $A15\text{'}\mathrm{s}$ exhibit a $T^2$ dependence in the temperature range $T_c<T\lesssim 40$ K, while ${\mathrm{Mo}}_3$Ge shows a $T^5$ dependence on temperature. Data are also presented for irradiated ${\mathrm{Nb}}_3$Sn which show that the $T^2$ power law is preserved for increasing residual resistivity $\rho \mathrm{}\left(0\right)\mathrm{}$. Previous analyses of $A15\mathrm{}$ resistivity are examined in some detail to show that the $T^2$ dependence in the low-temperature resistivity of high-$T_c$ $A15\mathrm{}$ materials is an intrinsic effect and is not crucially dependent on the real phonon structure in these materials. It is argued that the observed $T^2$ dependence remains an unsolved theoretical problem.