  In contrast to conventional s-wave superconductivity, unconventional (e.g. p
or d-wave) superconductivity is strongly suppressed even by relatively weak
disorder. Upon approaching the superconductor-metal transition, the order
parameter amplitude becomes increasingly inhomogeneous leading to effective
granularity and a phase ordering transition described by the Mattis model of
spin glasses. One consequence of this is that at low enough temperatures,
between the clean unconventional superconducting and the diffusive metallic
phases, there is necessarily an intermediate superconducting phase which
exhibits s-wave symmetry on macroscopic scales.
