1996/03/22 by K. M. Frahm, P. W. Brouwer, J. A. Melsen +1
Physics and Astronomy · #cond-mat
paper · pdf · doi:10.1103/physrevlett.76.2981
published as Phys. Rev. Lett. 76, 2981 (1996) · 4 pages, 2 figures, to appear in Phys. Rev. Lett
arxiv created 1996/03/22 · arxiv updated 2009/11/30
A theory is presented for the statistics of the excitation spectrum of a disordered metal grain in contact with a superconductor. A magnetic field is applied to fully break time-reversal symmetry in the grain. Still, an excitation gap of the order of δ opens up provided NΓ2\gtrsim 1. Here δ is the mean level spacing in the grain, Γ the tunnel probability through the contact with the superconductor, and N the number of transverse modes in the contact region. This provides a microscopic justification for the new random-matrix ensemble of Altland and Zirnbauer.