Andreev tunneling in charge pumping with SINIS turnstiles
  We present measurements on hybrid single-electron turnstiles with superconducting leads contacting a normal island (SINIS). We observe Andreev tunneling of electrons influencing the current plateau characteristics of the turnstiles under radio-frequency pumping. The data is well accounted for by numerical simulations. We verify the dependence of the Andreev tunneling rate on the turnstile's charging energy. Increasing the charging energy effectively suppresses the Andreev current. 
T. Aref, V. F. Maisi, M. V. Gustafsson, P. Delsing and J. P. Pekola
cond-mat.mes-hall