Role of Spatial Amplitude Fluctuations in Highly Disordered s-Wave Superconductors

Amit Ghosal; Mohit Randeria; Nandini Trivedi

doi:10.1103/PhysRevLett.81.3940

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Role of Spatial Amplitude Fluctuations in Highly Disordered s-Wave Superconductors

Amit Ghosal, Mohit Randeria, Nandini Trivedi

DOI 10.1103/PhysRevLett.81.3940 · Physical Review Letters

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Abstract

The effect of nonmagnetic 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 breakup of the system into superconducting “islands.” Superfluid density and off-diagonal correlations show a substantial reduction at high disorder. A simple analysis of phase fluctuations about the highly inhomogeneous BdG state is shown to lead to a transition to a nonsuperconducting state.