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

TL;DR

This paper calculates how impurities affect the density of states in a high-field superconductor, revealing a transition from a gapped to a gapless spectrum as disorder increases.

Contribution

It provides a detailed analysis of impurity effects on the density of states in a high magnetic field superconductor, highlighting the transition to a gapless spectrum.

Findings

At low energies, $N()\u223c ^2$ for weak disorder.

Strong disorder induces a finite density of states at the Fermi surface.

The spectrum becomes gapless due to high magnetic field and impurity effects.

Abstract

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, $N(\omega)\sim \omega ^2$ 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.