Exotic ground states and impurities in multiband superconductors

We consider the effect of isotropic impurity scattering on the exotic super conducting states that arise from the usual BCS mechanism in substances of cubic and hexagonal symmetry where the Fermi surface contains inequivalent but degenerate pockets (e.g. around several points of high symmetry). As ex amples we look at CeCo2, CeRu2, and LaB6; all of which have such Fermi surf ace topologies and the former exhibits unconventional superconducting behav ior. We find that while these non s-wave states are suppressed by non-magne tic impurities, the suppression is much weaker than would be expected for u nconventional superconductors with isotropic non-magnetic impurity scatteri ng.