Density of States below the Thouless Gap in a Mesoscopic SNS Junction
Abstract
Quasiclassical theory predicts an existence of a sharp energy gap Eg~ħD/L2 in the excitation spectrum of a long diffusive superconductor-normal metal-superconductor (SNS) junction. We show that mesoscopic fluctuations remove the sharp edge of the spectrum, leading to a nonzero density of states (DOS) for all energies. Physically, this effect originates from the quasilocalized states in the normal metal. Technically, we use an extension of Efetov's supermatrix σ model for mixed NS systems. A nonzero DOS at energies E<Eg is provided by the instanton solution with broken supersymmetry.
- Publication:
-
Physical Review Letters
- Pub Date:
- July 2001
- DOI:
- 10.1103/PhysRevLett.87.027002
- arXiv:
- arXiv:cond-mat/0012478
- Bibcode:
- 2001PhRvL..87b7002O
- Keywords:
-
- Condensed Matter - Mesoscale and Nanoscale Physics;
- Condensed Matter - Superconductivity
- E-Print:
- 4 pages, REVTeX