RANDOM-MATRIX THEORY OF A CHAOTIC ANDREEV QUANTUM-DOT

A new universality class distinct from the standard Wigner-Dyson class is identified. This class is realized by putting a metallic quantum d ot in contact with a superconductor, while applying a magnetic field s o as to make the pairing field effectively vanish on average. A random -matrix description of the spectral and transport properties of such a quantum dot is proposed. The weak-localization correction to the tunn el conductance is nonzero and results from the depletion of the densit y of states due to the coupling with the superconductor. Semiclassical ly, the depletion is caused by a singular mode of phase-coherent long- range propagation of particles and holes.