RUDERMAN-KITTEL-KASUYA-YOSIDA INTERACTION IN DIRTY SUPERCONDUCTORS

With the approximation that the energy gap is position independent, the static spin susceptibility in the superconducting state is completely determined by the normal-state Green functions. At low concentrations of nonmagnetic impurities, it is shown, by use of semiclassical approximations, that the usual type of Ruderman-Kittel-Kasuya-Yosida interaction acquires an additional random-phase shift. In systems where superconductivity and magnetism coexist such an effect will cause strong disorder in the magnetic phase akin to a spin-glass-like phase.