Abstract
We calculate the subgap density of states of a disordered single-channel normal metal connected to a superconductor at one end (normal-metal–superconductor junction) or at both ends [superconductor–normal-metal–superconductor (SNS) junction]. The probability distribution of the energy of a bound state (Andreev level) is broadened by disorder. In the SNS case the twofold degeneracy of the Andreev levels is removed by disorder leading to a splitting in addition to the broadening. The distribution of the splitting is given precisely by Wigner’s surmise from random-matrix theory. For strong disorder the mean density of states is largely unaffected by the proximity to the superconductor, because of localization, except in a narrow energy region near the Fermi level, where the density of states is suppressed with a log-normal tail.
- Received 21 March 2001
DOI:https://doi.org/10.1103/PhysRevB.64.134206
©2001 American Physical Society