Universal spectral statistics of Andreev billiards: semiclassical   approach
  The classification of universality classes of random-matrix theory has recently been extended beyond the Wigner-Dyson ensembles. Several of the novel ensembles can be discussed naturally in the context of superconducting-normal hybrid systems. In this paper, we give a semiclassical interpretation of their spectral form factors for both quantum graphs and Andreev billiards. 
Sven Gnutzmann, Burkhard Seif, Felix von Oppen, Martin R. Zirnbauer