Fluctuation Conductivity in Unconventional Superconductors near Critical Disorder

The fluctuation conductivity $\sigma_{\rm s}$ in bulk superconductors with non s-wave pairing and with nonmagnetic disorder of strength $D$ is studied at low $T$ and within the Gaussian approximation. It is shown by assuming a quasi two-dimensional (2D) electronic state that, only if the gap function $d_\mu({\p})$ is, as in a 2D p-wave pairing state, linear in the in-plane (relative) momentum ${\p}_\perp$, the in-plane fluctuation conductivity on the line $D=D_c$ is weakly divergent in low $T$ limit. The present result may be useful in clarifying the true gap function of spin-triplet ${\rm Sr_2RuO_4}$ through resistivity measurements.