Andreev conductance of chaotic and integrable quantum dots

We examine the voltage V and magnetic field B dependent Andreev conductance of a chaotic quantum clot coupled via point contacts to a normal metal and a superconductor. In the case where the contact to the superconductor domi nates, we find that the conductance is consistent with the dot itself behav ing as a superconductor-it appears as though Andreev reflections are occurr ing locally at the interface between the normal lead and the dot. This is c ontrasted with the behavior of an integrable dot, where for a similar stron g coupling to the superconductor no such effect is seen. The voltage depend ence of the Andreev conductance thus provides an extremely pronounced quant um signature of the nature of thr dot's classical dynamics. For the chaotic dot, we also study nonmonotonic reentrance effects that occur in both V an d B.