Transport through Double-Dots coupled to normal and superconducting   leads
  We study transport through double quantum dots coupled to normal and superconducting leads, where the Andreev reflection plays a key role in determining characteristic transport properties. We shall discuss two typical cases, i.e. double dots with serial or parallel geometry. For the parallel geometry, the interference of electrons via multiple paths is induced, so that the transmission probability has Fano-type dip structures which are symmetric with respect to the Fermi energy. We also investigate the Aharonov-Bohm(AB) effect for the parallel geometry. In some particular situations, we find that the general AB period for double dots, 4$\pi$, is reduced to 2$\pi$. 
Yoichi Tanaka, Norio Kawakami