Enhancement of parametric pumping due to Andreev reflection

We report properties of parametric electron pumping in the presence of a su perconducting lead. Due to a constructive interference between the direct r eflection and the multiple Andreev reflection, the pumped current is greatl y enhanced. For both quantum point contacts and double barrier structures a t resonance, we obtain exact solutions in the weak pumping regime showing t hat I-p(NS)=4I(p)(N), which should be compared with the result of conductan ce G(NS)=2G(N). Numerical results are also provided for the strong pumping regime showing interesting Andreev assisted pumping behavior. (C) 2001 Amer ican Institute of Physics.