Coherence-length dependence of fluctuations in the conductance of normal-superconducting interfaces

Bruun, J. and Hui, V. C. and Lambert, Colin (1994) Coherence-length dependence of fluctuations in the conductance of normal-superconducting interfaces. Physical review B, 49 (6). pp. 4010-4014. ISSN 0163-1829

Abstract

We compute sample-to-sample fluctuations in the electrical conductance G(NS) of mesoscopic normal-superconducting boundaries. If the superconductor is clean and the normal conductor diffusive, the rms deviation deltaG(NS) is approximately a factor of 2 larger than the universal value obtained for normal disordered conductors. This is consistent with predictions of random matrix theories and recent numerical simulations. If the normal material is clean, but the superconductor diffusive, the boundary conductance fluctuation is greater than deltaG(NS), by an amount which increases as the superconducting coherence length decreases. For a diffusive normal material in contact with a dirty superconductor, deltaG(NS) is insensitive to weak disorder in the superconductor, but decreases in the extreme dirty limit, where quasiparticles within the superconductor become Anderson localized.