Role of Spatial Amplitude Fluctuations in Highly Disordered s-Wave Superconductors
Abstract
The effect of non-magnetic impurities on 2D s-wave superconductors is studied beyond the weak disorder regime. Within the Bogoliubov-de Gennes (BdG) framework, the local pairing amplitude develops a broad distribution with significant weight near zero with increasing disorder. Surprisingly, the density of states continues to show a finite spectral gap. The persistence of the spectral gap at large disorder is shown to arise from the break up of the system into superconducting islands separated by regions with very small pairing amplitude. While the BdG superfluid density and off-diagonal correlations show a substantial reduction, amplitude fluctuations alone do not drive the system non-superconducting. A simple analysis of phase fluctuations in the highly inhomogeneous BdG state is shown to lead to such a transition.Keywords
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