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

Abstract

We have calculated the density of states $N(ω)$ of a dirty but homogeneous superconductor in a high magnetic field. We assume a dilute concentration of scalar impurities and find how $N(ω)$ behaves as one crosses from the weak scattering to the strong scattering limit. At low energies, $N(ω)\sim ω^2$ 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.