Possibility of Exciton Mediated Superconductivity in Nano-Sized Sn/Si   Core-Shell Clusters: A Process Technology towards Heterogeneous Material in   Nano-Scale
  We have produced Sn/Si core-shell cluster assemblies by a plasma-gas-condensation cluster beam deposition apparatus. For the sample with Si content = 12 at.%, the temperature dependence of electrical resistivity exhibits a metallic behavior above 10K and the onset of superconducting transition below 6.1 K. With decreasing temperature, the thermomagnetic curve for the sample with Si content = 8 at.% begins to decrease steadily toward negative value below 7.7 K, indicating the Meissner effect. An increase in the transition temperature, TC is attributable to exciton-typesuperconductivity. 
Yuichiro Kurokawa, Takehiko Hihara, Ikuo Ichinose, and Kenji Sumiyama
cond-mat.supr-con