Shot noise and Coulomb blockade of Andreev reflection

We derive low-energy effective action for a short coherent conductor between normal (N) and superconducting (S) reservoirs. We evaluate interaction correction $\ensuremath{\delta}G$ to Andreev conductance and demonstrate a close relation between Coulomb effects and shot noise in NS systems. In the diffusive limit doubling of both shot-noise power and charge in the carriers yields $|\ensuremath{\delta}G|$ four times larger than in the normal case. Our predictions can be directly tested in future experiments.