Andreev transport through double quantum dots: Numerical renormalization group approach

We study the transport through double quantum dots coupled to normal and superconducting leads. Using the numerical renormalization group method, we calculate the linear conductance due to the Andreev reflection. As the Coulomb interaction in the dots gets larger, we find that the peak of the conductance is suppressed, which clearly features the crossover between two distinct regions of spin-singlet ground state, i.e. the superconducting singlet state and the Kondo singlet state. It is further elucidated that this crossover becomes smeared with the increase in the interdot coupling, which causes the suppression of the peaks in the gate-voltage dependence of the conductance.