Superconducting cascade electron refrigerator
  The design and operation of an electronic cooler based on a combination of superconducting tunnel junctions is described. The cascade extraction of hot-quasiparticles, which stems from the energy gaps of two different superconductors, allows for a normal metal to be cooled down to about 100 mK starting from a bath temperature of 0.5 K. We discuss the practical implementation, potential performance and limitations of such a device. 
Maria Camarasa-Gomez, Angelo Di Marco (LPMMC), Frank W. J. Hekking   (LPMMC), Clemens Winkelmann (NEEL), Herv\'e Courtois (N...
cond-mat.supr-con