Transport properties of extended-<i>s</i>-state superconductors

Abstract

Superconducting states with extended-s-wave symmetry have been suggested in connection with recent angle-resolved photoemission experiments on ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$. In the presence of impurities, thermodynamic properties of such states reflect a residual density of states N(0) for a range of concentrations. While properties reflecting N(\ensuremath{\omega}) alone will be similar to those of d-wave states, transport measurements may be shown to distinguish qualitatively between the two. In contrast to the d-wave case with unitarity limit scattering, limiting low-temperature residual conductivities in the s-wave state are large and scale inversely with impurity concentration.