Density of states of a type-II superconductor in a high magnetic field: Impurity effects

We have calculated the density of states N(omega) of a dirty but homogeneous superconductor in a high magnetic field. We assume a dilute concentration of scalar impurities and find how N(omega) behaves as one crosses from the weak scattering to the strong scattering limit. At low energies, N(omega)similar to omega(2) for small values of the impurity concentration and scattering strength. When the disorder becomes stronger than some critical value, a finite density of states is created at the Fermi surface. These results are a consequence of the gapless nature of the quasiparticle excitation spectrum in a high magnetic field.