  We present a classical and quantum mechanical study of an Andreev billiard
with a chaotic normal dot. We demonstrate that in general the classical
dynamics of these normal-superconductor hybrid systems is mixed, thereby
indicating the limitations of a widely used retracing approximation. We show
that the mixed classical dynamics gives rise to a wealth of wavefunction
phenomena, including periodic orbit scarring and localization of the
wavefunction onto other classical phase space objects such as intermittent
regions and quantized tori.
